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A systematic review on the effect of the built and physical environment on mental health

Report prepared by Charlotte Clark, Bridget Candy and

Stephen Stansfeld for the Mental Health Foundation

Centre for Psychiatry

Wolfson Institute of Preventive Medicine Queen Marys School of Medicine & Dentistry

University of London

January 2006

Sections of this report were prepared in expert consultation with Ben Cave, Clair Chilvers (Director, NHS R&D Portfolio in Mental Health, DH), Sarah Curtis, Hugh Freeman, Lynne Friedli, Rowan Myron (Senior Researcher, Mental Health Foundation), and the Environmental Law Foundation, Health, Environment and Law Group.

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CONTENTS FIGURES AND TABLES............................................................................................................................ 3

EXECUTIVE SUMMARY .......................................................................................................................... 4

ABBREVIATIONS....................................................................................................................................... 6

STATISTICAL TERMS .............................................................................................................................. 6

INTRODUCTION ........................................................................................................................................ 7

METHOD...................................................................................................................................................... 7 SCOPE OF REVIEW: SUBJECT AREA .............................................................................................................. 7 EXPERT GROUP OF ADVISERS...................................................................................................................... 8 SEARCHING FOR THE EVIDENCE.................................................................................................................. 8

Search terms ......................................................................................................................................... 8 Search Strategy ..................................................................................................................................... 9 Data sources ......................................................................................................................................... 9

THE REVIEW PROCESS................................................................................................................................. 9 Eligibility screening of paper titles and abstracts ................................................................................ 9 Inclusion of studies ..............................................................................................................................10 Data extraction ....................................................................................................................................10 Data Synthesis......................................................................................................................................10

RESULTS.....................................................................................................................................................11 DATABASE SEARCHES................................................................................................................................11 EVIDENCE FOR ACCESS TO RESIDENTIAL GREEN OR OPEN SPACES .............................................................14 EVIDENCE FOR EXPOSURE TO NEIGHBOURHOOD VIOLENCE .......................................................................14 EVIDENCE FOR HOUSING OR NEIGHBOURHOOD QUALITY AND REGENERATION..........................................15

Housing and neighbourhood quality....................................................................................................15 Housing or neighbourhood regeneration.............................................................................................16

EVIDENCE FOR HOUSING TENURE ..............................................................................................................17 EVIDENCE FOR NEIGHBOURHOOD DISORDER .............................................................................................18 EVIDENCE FOR THE CHRONIC NOISE EXPOSURE DOMAIN............................................................................19 EVIDENCE FOR SPATIAL AND POPULATION DENSITY ..................................................................................20

Household spatial density ....................................................................................................................20 Population density ...............................................................................................................................20

EVIDENCE FOR URBAN BIRTH ....................................................................................................................23 ELEMENTS OF THE PHYSICAL OR BUILT ENVIRONMENT WHERE LITTLE EVIDENCE WAS IDENTIFIED...........24

DISCUSSION...............................................................................................................................................25 RANGE OF THE EVIDENCE ..........................................................................................................................25 STRENGTH OF THE EVIDENCE.....................................................................................................................25 IMPLICATIONS FOR FUTURE ENVIRONMENTAL DEVELOPMENTS .................................................................26 LIMITATIONS OF THE REVIEW ....................................................................................................................27

CONCLUSION............................................................................................................................................27

REFERENCES ............................................................................................................................................28 REFERENCE LIST OF INCLUDED PAPERS......................................................................................................28 PAPERS IDENTIFIED AS POTENTIALLY RELEVANT BUT UNABLE TO GET......................................................33 PAPERS EXCLUDED WITH REASON FOR EXCLUSION IN ITALICS...................................................................34 OTHER REFERENCES ..................................................................................................................................36

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APPENDIX 1. PREDICTORS: TERMS USED IN THE SEARCH STRATEGY DESCRIBING FEATURES OF THE PHYSICAL ENVIRONMENT.............................................................................37

APPENDIX 2. DATA EXTRACTIONS FOR FULL TEXT PAPERS INCLUDED IN THE REVIEW.......................................................................................................................................................................39

TABLE 1. ACCESS TO RESIDENTIAL GREEN OR OPEN SPACES AND MENTAL HEALTH ..................................39 TABLE 2. EXPOSURE TO STREET VIOLENCE AND MENTAL HEALTH.............................................................41 TABLE 3. HOUSING AND NEIGHBOURHOOD QUALITY AND REGENERATION AND MENTAL HEALTH.............45 TABLE 4. HOUSING TENURE AND MENTAL HEALTH ...................................................................................54 TABLE 5. NEIGHBOURHOOD DISORDER AND MENTAL HEALTH ..................................................................56 TABLE 6. NOISE AND MENTAL HEALTH......................................................................................................59 TABLE 7. SPATIAL/POPULATION DENSITY AND MENTAL HEALTH...............................................................64 TABLE 8 URBAN BIRTH AND MENTAL HEALTH...........................................................................................73 TABLE 9. URBANICITY (NOT SPECIFICALLY OR WEAKLY DEFINED) AND MENTAL HEALTH......................75 TABLE 10 ASPECTS OF PHYSICAL AND BUILT ENVIRONMENT WHERE A LACK OF RESEARCH EVIDENCE WAS IDENTIFIED ................................................................................................................................................76

FIGURES AND TABLES FIGURE 1: PROJECT FLOW CHART ...................................................................................................................13 TABLE 1. CITATION DATABASES SEARCHED, YEARS SEARCHED AND NUMBER OF CITATIONS IDENTIFIED ......12 TABLE 2: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE

ASSOCIATION BETWEEN LACK OF ACCESS TO GREEN OR OPEN SPACE AND MENTAL HEALTH.................14 TABLE 3: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE

ASSOCIATION BETWEEN EXPOSURE TO NEIGHBOURHOOD VIOLENCE AND MENTAL HEALTH. ................15 TABLE 4: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE

ASSOCIATION BETWEEN POOR NEIGHBOURHOOD AND/OR POOR HOUSING QUALITY AND MENTAL HEALTH.................................................................................................................................................16

TABLE 5: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE ASSOCIATION BETWEEN HOUSING/NEIGHBOURHOOD REGENERATION AND MENTAL HEALTH...............17

TABLE 6: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE ASSOCIATION BETWEEN RENTAL HOUSING TENURE AND MENTAL HEALTH. ..........................................17

TABLE 7: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE ASSOCIATION BETWEEN NEIGHBOURHOOD DISORDER AND MENTAL HEALTH........................................18

TABLE 8: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE ASSOCIATION BETWEEN CHRONIC NOISE EXPOSURE AND MENTAL HEALTH...........................................20

TABLE 9: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, FOR THE ASSOCIATION BETWEEN HOUSEHOLD SPATIAL DENSITY AND MENTAL HEALTH.....................................20

TABLE 10: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, AND THE ASSOCIATION BETWEEN HIGH POPULATION DENSITY AND PSYCHOLOGICAL MORBIDITY.......................22

TABLE 11: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, AND THE ASSOCIATION BETWEEN HIGH POPULATION DENSITY AND SCHIZOPHRENIA...........................................22

TABLE 12: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, AND THE ASSOCIATION BETWEEN LOWER POPULATION DENSITY AND SUICIDE ....................................................23

TABLE 13: NUMBER OF STUDIES IDENTIFIED, BY AGE GROUP AND HIGHEST LEVEL OF EVIDENCE, AND THE ASSOCIATION BETWEEN URBAN BIRTH AND SCHIZOPHRENIA. ...............................................................24

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Executive Summary Background & Aim There is a emerging body of evidence that the physical environment can affect mental health. The aim of this systematic review was to assess the strength of the evidence of the impact of the physical environment on mental health and well-being and to establish the level of evidence available, which could usefully inform legal cases evaluating health and environmental impacts. Method The systematic review identified studies published in English, in peer-reviewed journals between January 1990 and August 2005, which examined the effect of the physical or built environment on the incidence or prevalence of psychological morbidity. The physical environment was defined as relating to residential, neighbourhood or natural environments; mental health outcomes ranged from general psychological distress to more specific psychiatric diagnoses. The systematic review was undertaken with strict inclusion and exclusion criteria: studies included were reviews or primary research studies that examined populations of any age, including children, from industrially established market economy countries. Peer-reviewed papers were identified using several large citation databases (Medline, Embase, Psychinfo, Web of Science, BIDS, Geobase, ICONDA), relating to architecture, health, human geography, psychology and the social sciences. One reviewer screened all citations for eligibility and a second reviewer checked a random sample to ensure agreement on eligibility for inclusion in the review. One reviewer assessed the full text articles for eligibility; papers where eligibility was unclear were referred to a second reviewer. Papers eligible for the review were then subject to data extraction, which was undertaken using published guidelines for systematic reviews. One reviewer undertook data extraction, with a second reviewer double checking all data extraction summaries for accuracy. The information extracted from the papers was type of study design and study population, definition and measurement of the predictor(s), mental health outcome and how they were measured, main results and any adjustments made in the analysis for confounding factors, and any limitations or weaknesses of the study. Results In total 54,395 papers were identified using the search strategy, although there was a considerable degree of overlap in citation identification between the databases searched. Of these, 99 papers were identified which assessed the effect of the physical or built environment on mental health: 3 papers were systematic reviews, 2 papers were narrative reviews and the remaining 94 were primary research papers. The majority of papers were of cross-sectional design and there were fewer longitudinal studies. One-third of the studies used UK populations and the remainder were largely studies of European or North American populations.

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The papers were categorised into the following research domains: access to green spaces, exposure to neighbourhood violence, housing and neighbourhood quality and regeneration, housing tenure, neighbourhood disorder, chronic noise exposure, spatial and population density, and urbanicity. The methodological quality of the studies varied enormously, both within and across research domains, which affected the conclusions which could be drawn about the strength of the evidence for each domain. The strength of the evidence for environmental effects on mental health varied and was strongest for the effects of urbanicity on mental health: there was longitudinal evidence that urban birth was associated with schizophrenia, and that rural residence in adulthood was associated with suicide rates for males. Evidence for an effect of the neighbourhood on mental health was convincing: there was longitudinal evidence for exposure to violence in the neighbourhood and perceived neighbourhood disorder being associated with poorer mental health, as well as housing and neighbourhood regeneration being associated with improved mental health. There was cross-sectional evidence that chronic noise exposure was associated with poorer mental health, however the lack of longitudinal research in this domain limited this conclusion, as individuals with poorer psychological health are more likely to evaluate the environment negatively, bringing into question the direction of causality between noise exposure and mental health. Evidence for an effect of housing on mental health was weaker: robust longitudinal studies were few and cross-sectional studies in this area were often methodologically poor. Conclusion This review identified a range of peer-reviewed papers, which examined the association between the physical environment and mental health. The strength of the evidence varied and was strongest for the effects of urban birth (on risk of schizophrenia), rural residence (on risk of suicide for males), neighbourhood violence, neighbourhood regeneration and neighbourhood disorder. Evidence for an effect of housing on mental health was weaker. There was a lack of robust research in some areas and some aspects of the environment have been very little studied to date. The lack of evidence of environmental effects in some domains, does not necessarily mean that there are no effects: rather that they have not yet been studied. The evidence identified in this review will be utilised by the ELF Health, Environment and Law group, to establish possible implications for planning laws.

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Abbreviations ADHD Attention Deficit Hyperactivity Disorder dBA Measure of sound level in decibels (A-weighted to

approximate the typical sensitivity of the human ear). BSI Brief Symptom Inventory CES-D Centre for Epidemiologic Studies Depression Scale CDI Child Depression Inventory CIDI Composite International Diagnostic Interview CIS-R Revised Clinical Interview Schedule DH Department of Health DIS Diagnostic Interview Schedule DSL-90 Symptom Checklist- 90 DSRS Depression Self-Rating Scale EIA Environmental Impact Assessment ELF Environmental Law Foundation GHQ General Household Questionnaire HADS Hospital Anxiety and Depression Scale HEL Health, Environment and Law HIA Health Impact Assessment K10 Kessler 10 Scale KINDL Kindl Quality of Life Index LAeq Equivalent continuous sound level MHF Mental Health Foundation MHI Rand Mental Health Inventory MOS Medical Outcomes Study NGO Non-government Organisation NWS National Womens Study Depression Module ONS Office of National Statistics PANAS Positive and Negative Affect Scale PERI Psychiatric Epidemiology Research Instrument PTSD Post Traumatic Stress Disorder SAD Symptoms of Anxiety and Depression Scale SCL-90 The Symptom Checklist SDQ Strengths and Difficulties Questionnaire SF-36 Short Form 36 item General Health Survey SPHERE SPHERE measure of psychological and somatic symptoms Statistical terms CI Confidence interval NS Not significant or B Beta statistic SD Standard deviation SE Standard error

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Introduction The Environmental Impact Assessment (EIA) directive (85/337/EEC) ensures that the environmental consequences of planning decisions are taken into account, prior to planning consent being granted. During an EIA, evidence for the actual or potential impacts of the development on the environment are assessed, along with stakeholders opinions about the development, including those of the affected community. EIAs can also incorporate a Health Impact Assessment (HIA), as it is increasingly recognised that health is determined by a broad range of factors, including the environment. EIAs empower individuals and communities to protect the environment, ensure sustainable development and to protect human and environmental rights. The Environmental Law Foundation (ELF) is a national UK charity, linking communities and individuals to legal and technical expertise to prevent damage to the environment; it aims to increase awareness of how the law can be used to promote equitable, sustainable and healthy environments. Whilst there is an emerging body of evidence concerning the effect of the physical environment on mental health, the Environmental Law Foundation, Health, Environment and Law Group (HEL - a sub-group of ELF, with a specific focus on health, including mental health and well-being), identified the need to assess the level of evidence available, which can usefully inform legal cases evaluating health and environmental impacts. The aim of this systematic review was to assess the strength of the evidence of the impact of the physical environment on mental health and well-being. This systematic review was funded by the Mental Health Foundation (MHF) and conducted over 4 months (August-November 2005). Method Scope of review: subject area The aim of the review was to identify reviews and evaluative studies, both of qualitative and quantitative design, of the effect of the physical environment on mental health for children (including adolescents) and adults. For the purposes of this review, the physical environment was defined in terms of built and natural aspects of residential and neighbourhood environments. Work environments and the effects of conflicts or natural disasters on residential or neighbourhood environments were not included in the review. Mental health was defined in terms of symptoms of psychological well-being and diagnoses of psychiatric illness, including suicide.

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Expert group of advisers A panel of subject experts advised and assessed the findings, throughout the review process. Advice was obtained concerning the selection of data sources, the terms used in the search strategy, and the identification of key papers. The expert panel also commented on drafts of the final report. The experts and their affiliations are listed below. Ben Cave* Ben Cave Associates Ltd Clair Chilvers NHS R & D Portfolio in Mental Health, DH Sarah Curtis Queen Mary, University of London Hugh Freeman* Fellow, Green College, Oxford Lynne Friedli* Mental Health Promotion Specialist Rowan Myron Mental Health Foundation * Members of the ELF HEL group Searching for the evidence Search terms A list of search terms to describe the physical and built environment, mental health outcomes and research methodologies were compiled by the research team, in consultation with the expert panel. The search terms are briefly summarised below: see Appendix 1 for the complete list of search terms. The physical and built environment search terms related to:

1. the physical quality of housing and neighbourhoods in relation to tenure, household crowding, housing quality, waste disposal, chronic noise exposure, community facilities, maintenance, access to green/open space, traffic level, transport quality, and pollution.

2. the perceived sense of safety in the neighbourhood and exposure to violence in the neighbourhood.

3. spatial density/crowding in the home and neighbourhood.

The mental health terms related to: 1. general mental health (psychiatric disorder, psychiatric illness, mental

disorder, mental well being, mental stress, psychological health, psychological well being, psychological illness, mental health, mental illness).

2. specific mental illnesses (anxiety, stress disorder, phobic disorder, panic disorder, obsessive-compulsive disorder, compulsive behaviour, obsessive behaviour, mood, seasonal affective disorder, depression, depression postpartum, dysthymic disorder, psychosis, schizophrenia, Attention Deficit Hyperactivity Disorder, bipolar disorder, conduct disorder, hyperactivity, suicide).

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The research methodology terms related to the study design or type of review (systematic, review, random, trial, study, control, before and after, cohort, case control, cross-sectional, longitudinal, qualitative, prospective, retrospective, survey, intervention, observational). Search Strategy We planned, if feasible within the four month time limit, to identify published citation evidence from January 1980 to August 2005, of papers published in English, which explored the effect of the physical environment on mental health in populations from industrially established countries or regions. These included Australasia, Europe, Japan and North America. Due to the time constraints of the project, we only identified studies published in peer-reviewed journals: grey literature such as government and non-government organisation (NGO) reports, journal letters and book chapters were not included. Data sources Papers were identified using large citation databases (listed below), which were selected because they hold citation records from peer-reviewed publications in the subject areas of health, psychology, architecture, human geography and the social sciences (Weaver 2002). We also hand searched the journal Environment and Behaviour from 1995 to 20051. The reference lists of identified papers were additionally checked for further relevant studies. The expert panel checked a preliminary final list of references identified for the review, to ensure that the search process had been comprehensive. Evidence was identified from the following large citation databases: 1. Medline 2. Embase 3. Psychinfo 4. Web of Science 5. BIDS 6. Geobase 7. ICONDA. The review process Eligibility screening of paper titles and abstracts One reviewer (BC) screened all titles and abstracts of the papers identified from the search strategy, to assess eligibility for inclusion in the review. Eligibility screening was undertaken by year per citation database. To assess and reach an acceptable level of consistency and agreement on paper eligibility, the eligibility screening was double checked by a second reviewer (CC). Double checking was continued until the reviewers reached complete agreement, which was when approximately 10% of the individual year searches had been double checked. 1 1995, 1996, 1997 were incomplete collections.

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Inclusion of studies The full-text of the journal paper was retrieved (either electronically or in paper format) for potentially eligible papers. One reviewer (BC) undertook the text retrieval, read the paper and re-assessed eligibility. Where eligibility was unclear the paper was referred to a second reviewer (CC) for agreement on eligibility. Papers that were initially selected for inclusion by one reviewer (BC) were checked for eligibility by a second reviewer (CC). Data extraction Papers eligible for the review were then subject to data extraction which was undertaken according, where appropriate (depending upon study design), to published guidelines for systematic reviews (Begg 1996; Stroup 2000). For each paper descriptions of the methodology and findings were extracted by one reviewer (BC). All extractions were checked by a second reviewer (CC). The information extracted from the papers was: 1. Type of study design and study population (including age, gender, ethnicity,

indicator(s) of socioeconomic position and study response rate). 2. Definition and measurement of the predictor(s) aspects of the physical environment. 3. Mental health outcome(s) and how measured. 4. Main results and any adjustments made to the analysis for confounding factors. 5. Any limitations or weaknesses of the study in any of the above domains. The data extractions were categorised by the aspect of the physical environment under investigation into the following domains2. 1. Access to residential green or open spaces. 2. Exposure to neighbourhood violence. 3. Housing and neighbourhood quality and regeneration. 4. Housing tenure. 5. Neighbourhood disorder. 6. Noise. 7. Spatial/population density. 8. Neighbourhood population density. 9. Urbanicity. For each of these categories, results were collated for children (including adolescents) and adults. Where sufficient evidence was available, results were also differentiated by type of mental health outcome. A minority of studies (N=5) could not be categorised, as they examined a unique aspect of the physical or built environment, for which no other evidence was available. Data Synthesis A hierarchy of the strength of the quantitative evidence was applied to each extraction, relating to the robustness of the study design and findings, as well as any study limitations, using the Oxford Centre for Evidence-based Medicine Level of Evidence and 2 These domains were defined after data extraction, based upon the range of papers identified, and were not predetermined.

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Grades of Recommendation scale (http://www.cebm.net/levels_of_evidence.asp#levels). This is a well recognised, frequently used scale for summarising the level and strength of research evidence relating to health outcomes. The scale ranges from 1a (the highest level of evidence) to 4 (the lowest level of evidence). The specific levels of evidence are: 1a. Systematic review of randomised controlled trials with homogeneity of findings. 1b. Individual randomised controlled trials with narrow confidence intervals. 2a. Systematic review of cohort studies with homogeneity of findings. 2b. Individual cohort studies or poor quality randomised controlled trials. 3a. Systematic review (with homogeneity) of case-control studies. 3b. Individual case-control study. 4. Case-series (and poor quality cohort and case-control studies). In this systematic review, because of the heterogeneity of studies in terms of the study design, study population characteristics, the measurement of the physical and built environment and the measurement of mental health, it was not possible to conduct a meta-analysis to compare the homogeneity of findings of the identified studies. Results Database searches We searched the seven selected databases (Medline, Embase, Psychinfo, WOS, BIDS, GEOBASE and ICONDA). Due to time constraints, each database was searched back to 19903, rather than 1980 as originally planned. Table 1 shows the number of citations per database that were identified using our search strategy; the number of citations identified varied considerably by database, reflecting a difference in the number of papers available for the different disciplines covered by the databases. In total 54,395 citations were identified from a search of the seven databases, but there was a degree of overlap in citation identification between the databases. Figure 1 shows a flow chart, detailing the number of citations available at each stage of the search strategy. Screening of the citations identified 147 which were potentially relevant, of which 99 were included and 43 were excluded after full text retrieval; we were unable to retrieve a further 5 papers which were potentially relevant. Studies which were excluded at the full text retrieval stage, are listed in the Reference section, along with reasons for each exclusion.

3 GEOBASE was searched back only until 2000, because of a delay in access which reduced the time available to search the database and conduct data extraction.

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Table 1. Citation databases searched, years searched and number of citations identified

Database Years searched Number of citations identified Medline Embase Psychinfo WOS BIDS GEOBASE ICONDA

1990 to August 2005 1990 to August 2005 1990 to August 2005 1990 to August 2005 1990 to August 2005 2000-2005 1990 to September 2005

16,137 24,116 7,328 4,230 599 1,768* 217*

(search used mental health outcomes only) The search strategy identified 99 papers, which assessed the effect of the physical or built environment on mental health and well-being; 3 studies were systematic reviews, 2 were narrative reviews and the remaining 94 were primary research studies. During the project, we were unable to retrieve the full text for a further 5 papers. The design of the primary research studies varied, but the majority were of cross-sectional design. There were far fewer of the more robust studies of quantitative design such as randomised controlled trials or prospective cohort studies. Only one qualitative study was identified. The mental health outcomes assessed in the studies varied. The most frequent outcomes examined were general psychological well-being, depression, anxiety, schizophrenia and suicide. The majority of studies used validated scales to measure mental health and examined adult populations. One-third of the studies (32/94) examined UK populations. In terms of the physical or built environment, the studies covered several domains: access to green spaces, exposure to neighbourhood violence, housing and neighbourhood quality and regeneration, housing tenure, neighbourhood disorder, noise exposure, spatial density, population density and urbanicity. The following sections summarise and discuss the evidence for each of these domains and conclude with a table summarising the available level of evidence for each domain, using the Oxford Centre for Evidence-based Medicine Level of Evidence and Grades of Recommendation scale. The data extractions for each individual paper, by domain, are in Appendix 2.

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Figure 1: Project flow chart Citations identified

From database search = 54,395 Citations identified at

screening as potentially relevant = 147* Citations excluded

at full text = 43 Reasons:

Letter = 1 Study in progress = 1 Discussion paper = 9 Inappropriate sample = 5 Not mental health outcome = 8 Article superseded by another by same group = 5 Does not assess the effect of the built or physical environment = 14

Citations included after full text retrieval = 99

Type of physical or urban environment**: Urban birth = 7 Spatial density Household = 7 Neighbourhood = 23 Neighbourhood violence = 7 Neighbourhood disorder = 8 Neighbourhood/household quality = 11 Neighbourhood/household regeneration = 10

Housing tenure = 5 Noise = 11

Roads = 1 Pollution = 1 Territorial domestic space = 1 Green space =5 Public amenities = 1 Urban hassles =1

Five citations unable to get full text. **types of physical or urban environment does not add to total as some citations related to same study (but different analysis), while other citations have explore effect of several elements of the environment.

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Evidence for access to residential green or open spaces Five papers were identified that explored residential accessibility to green or open space and mental health (see Appendix 2: table 1 for data extractions). Four papers examined the effect in adults (Lewis and Booth 1994; Kaplan 2001; Kou and Sullivan 2001; McIntyre 2003), and one in children (Wells 2003). The papers explored the effect of gardens and natural areas, either available as views from the home or in terms of having physical access, on mental health. The studies varied in mental health outcome; three measured psychological distress including anxiety and depression, whilst two examined mental fatigue. Most studies used validated mental health measures. Two studies were conducted in the UK, both of which had study samples of several thousand adults (Lewis and Booth 1994; McIntyre 2003). All the studies found that having access, either as a view or through physical access, to green or open spaces such as gardens or natural areas was associated with better mental health (Table 2). However, this conclusion should be treated with caution as all of the studies were of less robust cross-sectional design: all except one (Kuo & Sullivan 2001), had poor response rates: and some used subjective measures of green space, such as self- or interviewer-ratings of access. Table 2 below summarises and evaluates the level of evidence for these studies. Table 2: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between lack of access to green or open space and mental health.

Age group A beneficial association No clear association A harmful association Children 0 0 1 (3b)* Adults 0 0 4 (3b)*

3b= evidence from cross-sectional study. Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. * In one study the association found was beneficial in that living nearby nature improved mental health outcome. Evidence for exposure to neighbourhood violence Seven studies were identified that explored the association between exposure to neighbourhood violence and mental health (Norris and Kaniasty 1994; Pastore 1996; Lai 1999; Mazza 1999; Moses 1999; Hurt 2001; Latzman and Swisher 2005) (see Appendix 2: table 2 for data extractions). One study was a prospective longitudinal cohort study (Norris and Kaniasty 1994) while the other studies were of cross-sectional design. Neighbourhood violence was defined as witnessing an arrest, mugging, shooting or stabbing, having possessions stolen or damaged, and being verbally or physically threatened or attacked. Six studies examined the effects of exposure to violence in child samples (Pastore 1996, Lai 1999, Mazza 1999, Moses 1999, Hurt 2001, Latzman & Swisher 2005) and one in adults (Norris and Kaniasty 1994). All studies used USA-based populations, except one which was undertaken in Canada (Lai 1999). The more robust longitudinal study (Norris & Kaniasty 1994) found that being a victim of property or violent crime was associated with poorer mental health for adults, 15 months after the crime occurred: victims of violent crime were also more psychologically

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symptomatic than victims of property crime. All of the cross-sectional studies in children found that being a witness or victim of crime was associated with poorer mental health: in one study this effect was found for females and not males (Moses 1999). Table 3 below summarises and evaluates the level of evidence for these studies. Table 3: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between exposure to neighbourhood violence and mental health.

Age group A beneficial association No clear association A harmful association Children 0 0 6 (3b)* Adults 0 0 1 (2b)

2b = evidence from longitudinal cohort study, 3b= evidence from cross-sectional study. Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. *In one study an association was found for females but not males; in another study the association was found for PTSD but not for depression or suicide.

Evidence for housing or neighbourhood quality and regeneration Housing and neighbourhood quality Ten studies (Saito 1993; Hopton 1996; Silveria and Ebrahim 1998; Evans 2000; Ellaway 2001; Evans 2002; Weich 2002; McIntyre 2003; Sundquist 2004; Galea 2005) and one review (Chu 2004) explored aspects of neighbourhood or housing quality and mental health (see Appendix 2: table 3a for data extractions). All of the primary studies defined neighbourhood quality using a number of characteristics including living in an area with derelict property, graffiti, lack of recreation space or private gardens, speeding traffic, high crime levels and uneven payments. Housing quality was also multifaceted in its definition and included living in damp homes, condensation problems, dissatisfaction with housing and desire to be re-housed. Half of the studies were conducted in the UK and the remainder were from Australia, Canada, Sweden and the USA. All the studies examined adult populations, except one (Evans 2002), which explored the effects of residential quality on childrens mental health. Only one study was a prospective longitudinal cohort study (Sundquist 2004) and the others were of cross-sectional design. One narrative review explored the effect of the physical environment on mental well-being (Chu 2004). The longitudinal cohort study followed a large sample of Swedish adults over an 8 year period, to examine associations between neighbourhood quality, defined as the level of destruction of public spaces, satisfaction with street cleanliness and the level of perceived neighbourhood noise, and psychiatric illness (Sundquist 2004). The study found no association between these aspects of neighbourhood quality and psychiatric illness. The cross-sectional studies demonstrated associations between poor housing or neighbourhood quality and mental health. However, some of these studies were limited by poor response rates. Table 4 below summarises and evaluates the level of evidence for these studies.

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Table 4: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between poor neighbourhood and/or poor housing quality and mental health.

Age group A beneficial association No clear association A harmful association Children 0 0 1 (3b) Adults 0 1 (2b) 9 (2b)

2b = evidence from a longitudinal cohort study, 3b= evidence from a cross-sectional study. Level of evidence score range 1 to 4 and a to b, with 1a being the highest value.

Housing or neighbourhood regeneration One systematic review (Thomson 2001 and 2003), one randomised controlled trial (Leventhal 2003) and six longitudinal studies (Dalgard and Tambs 1997; Evans 2000; Kahlweier 2000; Blackman and Harvey 2001; Blackman 2003; Huxley 2004 and Thomas 2005) explored the effects of housing or neighbourhood regeneration schemes on mental health (see Appendix 2: table 3b). Four of these studies compared residents who experienced housing or neighbourhood regeneration with control groups who did not experience housing or neighbourhood regeneration (Evans 2000; Kahlweier 2000; Blackman and Harvey 2001; Blackman 2003). Three of the studies were undertaken in the UK (Blackman and Harvey 2001; Blackman 2003; Huxley and Thomas 2005) and the rest were conducted in Europe and the USA. Several types of regeneration scheme were evaluated: neighbourhood regeneration encompassing improving deteriorated housing, repairing vandalised facilities, removal of graffiti, installing regular rubbish clearance, building new schools, playgrounds, sports and park areas: housing regeneration encompassing damp proofing, re-roofing and installing new windows in homes: and relocation to better housing and/or neighbourhoods. The effect of regeneration on mental health was measured up to 5 years after the implementation of the scheme. The systematic review identified 9 studies that explored the effects of housing and neighbourhood regeneration on mental health. Some of these studies are identified as primary research papers in this review, but some are not included as they were published before 1990 (Thomson 2001). The review found consistent evidence of an improvement in mental health after housing and neighbourhood regeneration but this conclusion was limited by a lack of detail about the design of the available studies. The randomised controlled trial found that a housing relocation scheme had a positive effect on the mental health of adults and male children, three years after implementation (Leventhal 2003). However, this effect was not found for female children. The six longitudinal studies all demonstrated a positive association between housing or neighbourhood regeneration and mental health, with one exception (Huxley 2004 and Thomas 2005), which found no improvement in mental health nearly two years after the implementation of a housing improvement scheme on a council estate. However, the consistent findings for the longitudinal studies should be treated with some caution, as four of the studies were affected by a low response rate. Table 5 below summarises and evaluates the level of evidence for these studies.

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Table 5: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between housing/neighbourhood regeneration and mental health.

Age group A beneficial association No clear association A harmful association Children 1(2b)* 0 0 Adults 7(2a-**) 1(2b) 0

2a= evidence from a systematic review, 2b = evidence from a longitudinal cohort study. Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. *In male children but not in female children. **A minus is applied as review under-reports the methods. Evidence for housing tenure Five studies were identified that explored the effects of living in rental accommodation on mental health (Ellaway 1998; Dunn 2002; Hiscock 2003; McIntyre 2003 Cairney 2005) (see Appendix 2: table 4). Three studies explored the effects of rental tenure on UK samples and the other studies were conducted in Canada. All studies explored the effects in adults, except one which used a child sample (Cairney 2005). All the studies were of less robust cross-sectional design. The findings of the studies were equivocal, with three studies demonstrating no association between housing tenure and mental health, one finding an association (Hiscock 2003) and another finding an association for only a sub-sample of adolescents, aged 12 to 14 years, but not for older adolescents (Cairney 2005). One explanation for the equivocal findings may be methodological weaknesses of the studies; all of the identified studies either have a low response rate or lack detail about the methodology of the study. Table 6 summarises and evaluates the level of evidence for these studies. Table 6: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between rental housing tenure and mental health.

Age group A beneficial association No clear association A harmful association Children 0 0 1* (3b) Adults 0 3 (3b) 1**(3b)

3b= evidence from a cross-sectional study. Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. *For children aged 12-14, not found in 15-19 year olds, ** The strength of the association is unclear: the effect may be related to other factors.

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Evidence for neighbourhood disorder Seven studies were identified that explored associations between neighbourhood disorder, such as crime and vandalism and mental health (Ross 2000; Ellaway 2001; Green 2002; Latkin and Curry 2003; Macintyre 2003; Christie-Mizell 2004; Ziersch 2005) (see Appendix 2: table 5). One further study explored the association between sense of belonging to the community and mental health (Young 2004). Two studies were of longitudinal design (Latkin & Curry 2003; Christie-Mizell 2004) and six were cross-sectional (Ross 2000; Ellaway 2001; Green 2002; Macintyre 2003: Young 2004; Ziersch 2005). All the studies examined adult samples, and one focused on older adults, aged 73-78 years (Young 2004). Three of the studies were conducted in the UK, three in the USA and two in Australia. The two longitudinal studies examined the effects of multiple characteristics of perceived neighbourhood disorder including vandalism, crime, derelict housing, litter, drug selling in the street, graffiti and teenagers hanging around, on mental health in North American populations (Latkin & Curry 2003; Christie-Mizell 2004). Despite contrasting follow-up periods, 9 months compared with 14 years, both studies found that perceived neighbourhood disorder was associated with poorer mental health. However, these results should be treated cautiously as neither study reports the response rate and although the Latkin & Curry study describes itself as a community sample, it is a community HIV outreach sample, which may limit representativeness. All of the cross-sectional studies that explored perceived neighbourhood disorder found that greater neighbourhood disorder was associated with poorer mental health. The study of sense of belonging, also demonstrated associations between positive perceptions of neighbourhood safety and neighbourhood community and better mental health. Table 7 below summarises and evaluates the level of evidence of these studies. Table 7: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between neighbourhood disorder and mental health.

Age group A beneficial association No clear association A harmful association Children 0 0 0 Adults 0 0 7 (2b)

Older adults 0 0 1 (3b) 2b = evidence from a longitudinal cohort study, 3b= evidence from a cross-sectional study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value.

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Evidence for the chronic noise exposure domain Eleven studies were identified that examined the effects of chronic noise exposure on mental health (Nivison & Endresen 1993; Saito 1993; Stansfeld 1996; Meister 2000; Haines et al 2001a; 2001b; 2001c; Lercher 2002; Ristovska 2004; Hardoy 2005; Stansfeld 2005) (see Appendix 2: table 6). One narrative review that summarised the effects of chronic noise exposure on health, including mental health was also identified (Stansfeld 2000). The studies examined the effects of chronic noise exposure on mental health for both children and adults and the majority of studies were carried out in Europe. Two studies were of robust longitudinal design: one of a child sample (Haines 2001a) and one of an adult sample (Stansfeld 1996); the rest of the studies were cross-sectional. The type of noise exposure examined varied from general ambient neighbourhood noise to source-specific road and aircraft noise exposure. Most studies measured chronic noise exposure using standardised noise metrics, although a couple utilised weaker measures such as residential distance from the noise source (Hardoy 2005) or perceived noise exposure (Saito 1993). All of the studies used validated measures of mental health. A longitudinal study of aircraft noise exposure in children (Haines 2001a) found that chronic aircraft noise exposure was not associated with mental health, after a one year follow-up. Evidence from cross-sectional studies of children is mixed: some studies have found no association between chronic noise exposure and overall mental health measures (Haines 2001b; Stansfeld 2005), whilst others have found an association (Lercher 2002; Haines 2001c). Evidence for effects on specific measures of child mental health such as hyperactivity and conduct disorder are similarly mixed: one cross-sectional UK study (Haines 2001c) found that aircraft noise exposure was associated with increased hyperactivity but not conduct disorder, whilst another study (Ristovska 2004) found that community noise exposure was not associated with hyperactivity but was associated with increased conduct disorder. The longitudinal study of noise exposure in male adults (Stansfeld 1996), found that exposure to road traffic noise was associated with higher scores for anxiety, over a 5 year period: no association was found between noise exposure and depression. A recent cross-sectional study supports these findings (Hardoy 2005) and also demonstrated an association of noise with anxiety but not depression. There is further cross-sectional support for an association (Meister 2000), although one study, with a small sample size found no association between objective noise measurements and anxiety and depression (Nivison & Endresen 1993). Subjective responses to noise exposure, such as annoyance and potential mediating factors such as noise sensitivity were associated with mental health outcomes (Nivison & Endresen 1993; Saito 1993) but these cross-sectional studies are limited as they may confound the perception of noise with psychological state. Table 8 below summarises and evaluates the level of evidence of these studies.

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Table 8: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between chronic noise exposure and mental health

Age group A beneficial association

No clear association A harmful association

Children 0 3 (2b) 3 (3b)* Adults 0 1 (3b) 4 (2b)

2b = evidence from a longitudinal cohort study, 3b= evidence from a cross-sectional study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. *One study found effect for social adaptability and opposing behaviour but not hyperactivity or anxiety No association for objective noise but association observed for subjective noise. Two studies found effect for anxiety but not depression. Evidence for spatial and population density Household spatial density Seven studies explored the effects of spatial density in the household on mental health (Saito 1993; Ruback 1994; Maxwell 1996; Sadowski 1999; Agerbo 2001; Evans 2001; Wahlbeck 2001) (see Appendix 2: table 7a). Three studies were of longitudinal design (Saito 1993; Sadowski 1999; Wahlbeck 2001) and the rest were cross-sectional studies. Five studies explored the effect of spatial density for adult samples and two examined the effects for children (Agerbo 2001; Evans 2001). Whilst one of the longitudinal studies found an association between high spatial density in the household during childhood and adult mental health for males but not females (Sadowski 1999), the other two studies demonstrated no association, suggesting that high household spatial density in childhood is not associated with poorer mental health in adulthood. The cross-sectional studies of adult populations support this conclusion, as they also found no association between current household spatial density and mental health. The cross-sectional studies of children (Maxwell 1996; Evans 2001) suggest that children from crowded, high spatial density homes may have poorer psychological health, but both these studies have methodological limitations, including small sample sizes and unreported response rates. Table 9 below summarises and evaluates the level of evidence for these studies. Table 9: Number of studies identified, by age group and highest level of evidence (in brackets), for the association between household spatial density and mental health.

Age group A beneficial association No clear association A harmful association Children 0 0 2 (3b) Adults 0 4 (2b) 1 (2b)*

2b = evidence from a longitudinal cohort study, 3b= evidence from a cross-sectional study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. one study examined behavioural disturbance as the outcome *In one study a harmful association was found in male subgroup only

Population density A systematic review from one research group (McGrath 2004; Saha 2005) and twenty one studies were identified that examined the effects of population density and mental

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health (Parikh 1996; Saunderson 1998; Kennedy 1999; Turner Goins 1999; Schelin 2000; Allardyce 2001; Singh 2002; Lehtinen 2003; Oliver 2003; Weich 2003; Caldwell 2004; Otsu 2004; Peen 2004; Spauwen 2004; Sturm 2004; Wang 2004; Walters 2004; Fraser 2005; Levin 2005; Propper 2005; Rohrer 2005) (see Appendix 2: table 7b). The majority of studies were of cross-sectional design and only two were longitudinal (Lehtinen 2003; Spauwen 2004). Unfortunately, not all of the studies provided definitions of population density: those that did grouped the study population into 3 to 5 categories based upon the number of people per km or the total population living in an area. A range of mental health outcomes were evaluated including psychological distress (depression and anxiety), schizophrenia and suicide; as there were several studies in this domain, it was possible to describe and evaluate the evidence individually for each of these outcomes. Psychological distress Eleven studies explored the association between population density and rates of depression and anxiety in adults. All studies were of cross-sectional design. Depression and anxiety were measured using validated scales and covered differing levels of severity of psychological distress. The studies were conducted in the UK, USA, Canada and Scandinavia. The only cross-national study found that there was an increased risk of depressive disorder for women living in high density urban areas, but this association was only found for women in the UK and Ireland: strangely no similar association was observed for Finnish or Norwegian women (Lehtinen 2003). However, there are some methodological anomalies for this paper, which suggest that caution should be given to the findings: firstly, the confidence intervals for the odds ratio for the Irish sample are extremely wide (95% CI 1.09, 303.80), suggesting that the data for the sample lacks power: secondly, few adjustments were made to the analysis for specific socio-economic factors, which may confound the association between population density and mental health. The results of the other cross-sectional studies are also equivocal: some studies have found that there is no clear association between population density and mental health (Parikh 1996; Sturm 2004; Propper 2005) while others have found that higher population density was associated with higher rates of psychological morbidity (Oliver 2003; Wang 2004; Weich 2003; Rohrer 2005). Furthermore, some studies suggest that these associations are evident only in specific sub-groups. In one American study an association was found for the suburban residents and not for the urban or rural residents (Rohrer 2005) and a recent UK study found an association between population density and depression but only for individuals who were resident in urban areas and who were economically inactive (Weich 2003). Two studies explored the effects of population density for older adults (Turner Goins 1999; Walters 2004): the UK study suggested that living in an area of higher residential density was associated with an increased risk of depression and anxiety (Walters 2004), whilst the American study found that within rural areas, living in high density areas was associated with fewer depressive symptoms (Turner Goins 1999). Table 10 below summarises and evaluates the level of evidence for these studies.

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Table 10: Number of studies identified, by age group and highest level of evidence (in brackets), and the association between high population density and psychological morbidity

Age group A beneficial association No clear association A harmful association Children 0 0 0 Adults 1(3b) 3 (3b) 5* (3b) Older adults 1(3b)** 0 1 (3b) 3b= evidence from a cross-sectional study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. Declining rural population associated with poorer mental health *In one study in the female population in UK and Ireland not in Norway or Finland, in another increased risk for those in suburban area only, and in another study association only found for those who were not employed. **In a rural population

Schizophrenia The association between population density and schizophrenia was explored in one longitudinal cohort study (Spauwen 2004) and three cross-sectional studies (Schelin 2000; Allardyce 2001; Peen 2004). A systematic review was also identified (McGrath 2004; Saha 2005) but this review did not describe how the previous studies defined urbanicity. The more robust, longitudinal study found no association between population density and schizophrenia in a sample of young German adults followed up over a 4 to 5 year period (Spauwen 2004); whilst the three less robust, cross-sectional studies found that higher population density was associated with increased rates of schizophrenia. However, one of these studies found that the urban-rural difference observed in rates of schizophrenia between rural Dumfries and Galloway and urban Camberwell, were explained by the high incidence of non-whites in urban Camberwell (Allardyce 2001). The systematic review found equivocal evidence for an association between high population density and schizophrenia: an association was found for incidence rates of schizophrenia but not for prevalence rates. The authors suggest that this difference may have been because the prevalence analysis included more data from developing countries, than the incidence analysis, but this explanation is unconvincing. Table 11 below summarises and evaluates the level of evidence for these studies. Table 11: Number of studies identified, by age group and highest level of evidence (in brackets), and the association between high population density and schizophrenia

Age group A beneficial association No clear association A harmful association Adults 0 3 *(2b) 2(3b) 2b = evidence from a longitudinal cohort study, 3b= evidence from a cross-sectional study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. *One study found no effect after adjusting for ethnicity.

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Suicide Six cross-sectional studies examined the association between population density and rates of suicide (Saunderson 1998; Singh 2002; Otsu 2004; Caldwell 2004; Kennedy 2005; Levin 2005). Studies were undertaken in the UK, as well as Australia, Japan and the USA. All these studies used national suicide mortality data over one or more years, except one which used suicide data from London boroughs (Kennedy 1999). All of the studies provided findings separately for male and female samples, with one exception (Kennedy 1999). Living in more sparsely populated areas was associated with higher rates of suicide in males (Saunderson 1998; Singh 2002; Caldwell 2004; Levin 2005). In the North American study, the suicide rate was double for rural areas, compared with urban areas (Singh 2002). These findings are supported by a Japanese study which found that males living in areas of economic development with high population density had a lower risk of suicide (Otsu 2004). The evidence concerning an association between population density and suicide for females was equivocal with three studies finding no effect and two studies, which provided analysis stratified by age group, demonstrating an association. One Australian study (Caldwell 2004) found that women aged 30-44, living in areas of medium population density had a higher rate of suicide compared with their counterparts in rural and urban areas and an American study found that rates of suicide were higher for women aged 15-24 living in the least populated areas (Singh 2002). One study, which focused on urban areas London boroughs, found that greater population density and higher deprivation was associated with an increased risk of suicide (Kennedy 1999). Table 12 below summarises and evaluates the level of evidence for these studies. Table 12: Number of studies identified, by age group and highest level of evidence (in brackets), and the association between lower population density and suicide

Age group A beneficial association No clear association A harmful association Adults 1(3b) 0 5* *(3b) 3b= evidence from a cross-sectional study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value. **In one study living in urban areas had a lower risk of suicide Evidence for urban birth Longitudinal cohort studies which explored the effects of urban versus non-urban birth and the development of schizophrenia in adulthood were identified from Denmark (Eaton 2000; Agerbo 2001; Pedersen 2001; Van Os 2004), the Netherlands (Marcelis 1998 and 1999) and Finland (Haukka 2001) (see Appendix 2: table 8). The Danish studies were carried out by the same research group and utilised the same data set. All of the studies defined urbanicity of birth place using measures of population density and used data from national registers to measure schizophrenia in adulthood. All of these longitudinal studies found an association between being born in an urban area and schizophrenia, with most studies identifying an increasing gradient of risk with increasing urbanicity. Haukka (2001), in comparing the strength of association in

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different cohorts born between 1950-1969, found that the risk for urban born individuals increased and was stronger for the younger cohorts. An interesting study in the Netherlands examined not only the effect of urban birth, but also its interaction with urbanicity of area of residence in adulthood. This study found that individuals who were born in urban areas, but did not live in an urban area in adulthood were at greater risk of schizophrenia compared with those who were born in rural areas but resident in urban areas as adults (Marcelis 1999). Table 13 below summarises and evaluates the level of evidence for these studies. Table 13: Number of studies identified, by age group and highest level of evidence (in brackets), and the association between urban birth and schizophrenia.

Age group A beneficial association No clear association A harmful association Adults 0 0 7 (2b) 2b = evidence from a longitudinal cohort study Level of evidence score range 1 to 4 and a to b, with 1a being the highest value.

Elements of the physical or built environment where little evidence was identified There were six research domains where minimal studies (only one or two papers) were identified: these were remoteness, community amenities, pollution, road improvements, urban hassles and territorial spaces in the home. These studies were all of cross-sectional design. Data extractions for these studies are provided in Appendix 2: table 10.

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Discussion Range of the evidence This review identified 99 papers that have examined the association between the physical environment and mental health. The papers identified examined a range of environmental factors and mental health outcomes including access to green spaces, exposure to neighbourhood violence, housing and neighbourhood quality and regeneration, housing tenure, noise exposure, household and population density, and urban birth. One of the conclusions of this review is that there is a lack of robust research in some of the domains that have been examined previously and some aspects of the environment have been very little studied to date. It was surprising that no peer-reviewed journal papers, examining the longitudinal effects of major developments, such as changes to transport infrastructures and facilities, on mental health were identified. It is possible that studies of this type may be published in the future, given the more recent focus on environmental and health impact assessment methods in Europe and the evaluation of large scale developments upon the population. This implies that the absence of evidence of environmental effects in some domains does not necessarily mean there are no effects simply that they have not been studied. Strength of the evidence The methodological quality of the studies identified by this systematic review varied enormously, both within and across domains. This affected the conclusions which could be drawn about the strength of the evidence for each domain. The most compelling evidence for an environmental effect on mental health comes from studies of the effect of urban environments, usually defined by population density, on mental health. Longitudinal studies have found consistent evidence for an association between urban birth and schizophrenia, as well as an association between rural residence in adulthood and suicide rates for males, but not females. The association between rural residence and suicide may relate to a lack of employment opportunities in rural areas. However, evidence for an association between urbanicity and broader psychological distress, such as depression and anxiety, is more equivocal and there are a lack of longitudinal studies in this area. There was also some cross-sectional evidence for an effect of chronic noise exposure on mental health, although the findings by type of disorder are more consistent for adults than children. Adult mental health was also associated with subjective rather than objective measures of noise exposure, such as noise annoyance. There is evidence that noise annoyance is not on the pathway between noise exposure and mental health. There is a need for further longitudinal studies in this domain and the cross-sectional conclusions should be treated cautiously, as individuals who are experiencing poor mental health are more likely to also evaluate the environment negatively, bringing into question the direction of causality between subjective assessments of noise exposure and mental health.

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Studies have found little association between household density and mental health, either cross-sectionally or longitudinally. However, household density and social disadvantage may be confounded in these studies, as most studies do not make adequate adjustment for socioeconomic factors. Evidence for associations between household tenure and mental health was similarly limited by inadequate adjustment for socioeconomic factors: cross-sectional evidence for an association between rental tenure and poorer mental health was weak, but the studies were additionally limited by other methodological weaknesses, including poor response rates. As expected, there was evidence for an association between exposure to violence or crime in the neighbourhood and poorer mental health, particularly for children; although the majority of evidence was cross-sectional. However, these findings need to be interpreted with some caution, as we would expect that being the victim of crime would be associated with poorer mental health. It is difficult to theorise what contribution the physical aspects of the neighbourhood environment would play in this association: possibly, poorly designed neighbourhood environments may allow opportunities for criminals to take advantage of people where they are not overlooked. Another suggestion comes from the consistent longitudinal and cross-sectional evidence that perceived neighbourhood disorder, such as vandalism, lack of facilities, vacant housing and litter, was associated with poorer mental health. These environmental aspects illustrate one way in which the environment may mediate the effect of exposure to crime on mental health. However, it is difficult to disentangle these associations as individuals with poorer mental health are likely to be selected into poorer neighbourhoods. Overall, evidence for an effect of housing quality on mental health was mixed: there was no longitudinal evidence for an association and the cross-sectional studies which demonstrated an association were limited by poor response rates. In contrast, consistent longitudinal evidence was available for housing and neighbourhood regeneration improving mental health. There was also consistent cross-sectional evidence that access to green or open spaces was also associated with better mental health, but again these findings were limited by poor study response rates. One important finding of this review is the need for methodologically stronger research in the domains examining the effect of housing quality and facilities on mental health: more specifically, these associations need to be examined with larger sample sizes, as well as longitudinally, which would enable the causal relationship between the environment and mental health to be examined in more detail. Implications for future environmental developments It is beyond the scope of this systematic review to examine the implications of the strength of the evidence identified herewith for legal cases evaluating the health and environmental impacts of planning developments. The evidence identified in this review will be reviewed by the ELF Health, Environment and Law Group, and a further publication prepared, detailing the possible implications of the evidence for planning laws.

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Limitations of the review This review was extensive in sourcing evidence, which led to a vast number of citations being identified. Due to time constraints of the review, only one reviewer scanned all of the identified citations for eligibility. A weakness of the review was that this stage was not undertaken independently, by two reviewers. However, a 10% sample of the searches were screened independently by a second reviewer and this second screening process was only terminated when the checks per year reached 100% agreement. We also sent the panel of experts a preliminary final list of references, for the identification of omissions: no omitted studies were identified, suggesting that the search strategy had been comprehensive. Conclusion In conclusion, this review identified a range of peer-reviewed papers, which have examined the association between the physical environment and mental health. The majority of papers were cross-sectional and there were more studies of adult than child populations. The strength of the evidence for environmental effects on mental health varied and was strongest for urban birth (on risk of schizophrenia), rural residence (on risk of suicide for males), neighbourhood violence, neighbourhood regeneration and neighbourhood disorder. Evidence for effects of housing on mental health was weaker: robust longitudinal studies were few and many of the cross-sectional studies were methodologically poor. The evidence identified in this review will be utilised by the ELF Health, Environment and Law group, to establish possible implications for planning laws.

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