Psychopathology and the development of disability

Soc Psychiatry Psychiatr Epidemiol (1997) 32:379-386 �9 Springer-Verlag 1997

A.C. Kouzis �9 W . W . Eaton

Psychopathology and the development of disability

Accepted: 5 November 1996

Abstract The objective was to determine the effect of preexisting psychopathology on days missed from work or usual activities ("disability days") in a large community sample (N = 3481). Logistic regression analyses were performed with the presence or absence of disability days (wave 2) as the dependent variable. The effects of sociodemographic variables, six psychiatric disorders, a high distress score, and chronic physical conditions (wave 1) were studied. Separate analyses were conducted for the total sample and four subgroups (labor force participants, homemakers, men, and women). The adjusted odds ratios and 95% confidence intervals (95% CI) for subjects with onset of panic disorder were 7.3 (95% CI = 1.8,28.7); for those with chronic major depressive disorder, 7.2 (95% CI = 0.3,160.6); and for those with chronic high distress, 5.0 (95% CI = 2.6,9.9). The relative odds for developing a disability were greater for those with either type of psychiatric disorder or high distress than for those with any prior physical illness or those with a prior disability day. Disability days experienced by persons with psychopathology result in diminished quality of life, economic losses, and increased need for health services. Improved health services and educa- tional and work adjustments for emotionally disabled persons are recommended.

Introduction

Restricted activity days, or disability days, experienced by persons is an important measure of functioning

A.C. Kouzis ( ~ ) . W.W. Eaton The Johns Hopkins University, School of Hygiene and Public Health, Department of Mental Hygiene, 624 North Broadway, Baltimore, MD 21205, USA

status and well-being (Golden 1986; Patrick et al. 1988; Scholes et al. t991; Stanfield et al. 1995). Persons with depression, schizophrenia, alcohol and other drug abuse or dependence experience functional disabilities that limit their lives and ability to relate to others both socially and occupationally. The association between depressive disorders and disability has been recently recognized as detrimental to work productivity and efficiency (Broadhead et al. 1990; Craig and Van Natha 1983; Mintz et al. 1992; Turner and Noh 1988; Von Korffet al. 1992). Days lost from work, a reduced sense of well-being, and a need for health services are often an outcome of psychopathology. Disabilities are significant for policy makers who make decisions regarding economic losses and for the provision of services in the society.

The 1978 US Social Security Survey of Disability and Work estimated that 1.1 million adults in households, or about 1% of the adult population, were seriously disabled mentally ill. These figures represent- ed only those in households and those between the ages of 20 and 64 years, they focused only on those receiving payments for work disability and considered only cases of at least 1 years duration (Ashbaugh et al. 1983). The National Health Interview Survey (NHIS) of 1989 found 2.8 million adults 18 years or older living in households, or about 1.6% of the adult population, who were either unable to work or limited in their work because of their severe mental illness (Barker et al. 1989). These were based on reports of household mem- bers' specific diagnoses reported by a single respondent in the household. Other surveys of psychiatric disorders have found more than 15% of the population have a mental disorder (Kessler et al. 1994; Robins et al. 1991). Thus, it is expected that many more people experience either a less severe, or a temporary, disability ("disability day") than those recognized as mentally disabled by the Social Security Administra- tion or those included in the Health Interview Surveys (Okpaku et al. 1994).

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Previous studies estimated associations of various measures of functioning with specific chronic medical conditions; few comparisons were made with patients experiencing distress or psychopathology (Mintz et al. 1992). Studies on physical functioning that included mental illness were restricted to psychological distress or depressed mood (Bruce et al. 1994; Frerichs et al. 1982; Neff et al. 1980; Satin and Morrett 1985; Selzer et al. 1968) and failed to adjust statistically for physical condition. Others have examined the relationship between depression and functional disability among patient samples (Gardiner 1980; Rutter 1977; Shaffer et al. 1972; Wells et al. 1989). Wells et al. (1989) focused on depression, citing its "association with large decre- ments in patient well-being and functioning." Ormel et al. (1993) found depression and anxiety were associated with mild to moderate disability, and that severity of psychiatric illness and disability show synchrony of change.

There are few studies on psychopathology and disability days. Von Korff et al. (1992), in a 1-year follow- up study of 185 medical patients who were high utilizers of ambulatory health care, found a relation between disability measures that included disability days and depression. Broadhead et al. (1990) investigated the relationship between psychopathology and disability days, but examined only depression and depressive symptoms. Persons with major depression experienced almost five times greater risk of disability days in their community study. A significant association between physical functioning, including bed days in the last 2 weeks and affective and anxiety disorders, was dem- onstrated by Wells et al. (1988) in Los Angeles. How- ever, their analysis was restricted to cross-sectional data and to interviews with non-Hispanic whites and Mexican Americans. In the United Kingdom, Jenkins (1985) found one-third of executive civil servants reported minor psychiatric morbidity.

Depression may be related to disability because it is associated with non-psychiatric medical conditions. A positive relationship has been found between physical illness and depression or psychological distress (Aneshensel et al. 1984; Craig and Van Natta 1983; Kathol and Petty 1981; Langer and Michael 1963; Neff et al. 1980). Significant differences in mental health were found to exist between patients without chronic physical conditions and those with any of five chronic physical conditions studied by Stewart et al. (1989). This differs from a few previous studies showing no such effect (Cassileth et al. 1984; Mason et al. 1983). A number of studies (Berkman et al. 1986; Craig and Van Natta 1983; Earle et al. 1979; Kasl and Cobb 1969; Rosenbaum and Raz 1977; Turner and Noh 1988) show the physically disabled to be signifi- cantly more depressed, or more psychologically dis- tressed generally, although others disagree (Crown and Crown 1973; Nelson and Gruver 1978; Stern et al. 1976).

Psychiatric disorders have also been linked with disabilities resulting from injuries. Paranoid ideation, clinical depression, and social stress have been sus- pected as possible causes of injuries (Holt 1981; Selzer et al. 1968). An association between affective distur- bances and disabling injuries among 18- to 64-year- olds and phobic symptoms and disabling injuries for 65- to 74-year-olds has been suggested by Aboraya (1991).

In sum, research on disability days to date has focused on general mental health of the physically challenged, on injuries, or on the depressed versus the non-depressed. There is little research tracing the evolution of psychopathology and disability in the general population. Recent longitudinal evidence has utilized patient samples in primary care (OrmeI et al. 1993; Von Korff et al. 1992) or been limited to depression (Aneshensel et al. 1984; Broadhead et al. 1990; Mintz et al. 1992; Von Korff et al. 1992; Wells et al. 1992), from which generalization to other psychopathology or the general population remains difficult.

Our prior analyses at baseline produced significant odds ratios of the effects of sociodemographic characteristics and psychopathology on disability days for emotional reasons only, for those employed full time in the labor force (Kouzis and Eaton 1994). Sub- jects with major depressive disorders had the strongest association with disability, with a 27 times greater likelihood of being absent from work for emotional reasons. Those with a panic disorder followed closely, with an odds 20 times that of others of missing work. Comparing the odds of absenteeism for physical health reasons, only respondents with cardiovascular disease or cancer were more likely to experience a disability day.

This paper, in contrast, has focused on 9eneral disability days, because it is felt that psychiatric problems may be an important cause of disability days, not necessarily labeled as emotional by respondents. For example, psychopathology may lead to physical conditions through a direct biological action ("psychoso- matic disorder") or through its effects on prevalence or curative health behaviors. Alternatively, respondents may label days not at work as deriving from physical illness, when in fact they are due to psychopathology ("mental health days").

The research reported here considers days missed from work or usual activities ("disability days") associated with a range of specific psychiatric disorders and psychosocial distress. Longitudinal data from a community survey permit an examination of the relevance of changes in psychiatric disorders to the development of disability. We assess and adjust for the influence of sociodemographic characteristics on these relationships. Further, the analysis statistically controlled for the effects of chronic medical conditions.

38t

Methods

Study sample

The sample was drawn from the Eastern Baltimore Mental Health Survey conducted during 1981 as part of the National Institute of Mental Health (NIMH) Epidemiologic Catchment Area (ECA) Pro- gram (Eaton and Kessler 1985; Eaton et al. 1981; 1984). It has recently been reported (Public Health Newsletter 1992) that East Baltimore has "the highest rates of premature disability and death in the state." The ECA program is a series of epidemiologic surveys conducted by university-based researchers in five metropolitan communities in the United States. This paper reports analyses from The Johns Hopkins University site of the ECA program.

The Baltimore site included three contiguous mental health catchment areas with an adult population of approximately 175,000. The data include information on 2768 individuals originally identified through a probability sample of adult household residents who were interviewed regarding their health, mental health, and health services use, and who were located and successfully reinterviewed 1 year later. The response rate in the first wave of the East Baltimore sample was 78%, and there was about 20% attrition between waves (Eaton et al. 1992; Von Korff 1985). Details concerning the characteristics of this population have been presented elsewhere (Eaton et al. 1984; Eaton and Kessler 1985).

Measurement

Each participant in the survey underwent a 90-min interview that included the National Institute of Mental Health Diagnostic Inter- view Schedule (DIS), which was scored to reflect DSM-III diagnoses (hence the label "DIS/DSM-III disorder") (American Psychiatric Association 1987; Robins et al. 1981). At follow-up symptoms experienced within the previous year were counted only if they met the severity criteria of the DIS and were not explained by physical illness, medications, alcohol, or other drug use.

Incidence, remission, and chronicity were determined for each of the psychiatric disorders. Cases where subjects were negative at baseline and positive at follow-up were deemed "onset" cases, those where subjects were positive at baseline and negative at follow-up we called "remission," and those where the subjects were positive at both baseline and follow up became "chronic" cases. Thus, for each of the six disorders and distress there were four categories: no diagnoses (reference category), incidence, remission, and chronicity.

Several sets of variables included in the Eastern Baltimore site of the NIMH's ECA program were not included in other ECA sites. The Baltimore site included the General Health Questionnaire (GHQ) to measure distress that might not be connected to a specific mental disorder. The GHQ was designed for study of the relationship of psychiatric problems to general heaRh care utilization, and has good psychometric properties (Goldberg 1972). The standard threshold of 4 points or more was used to define those in the sample considered to be at "high distress."

In the follow-up interview respondents were asked questions pertaining to disability over the previous 3 months. Specifically, they were asked, "During the last 3 months, were there any times when you were kept from your work, school, or usual activities for at least 1 whole day because of an injury or because you weren't feeling well?" Prior disability status as determined at baseline refers to having 1 or more disability days for emotional problems, physical conditions, or injuries. As in the Health Interview Surveys, 3 months was selected as our recall period, a compromise offering an adequate number of responses and necessary recency. The questions on disability days are used in many health surveys in the US and their reliability and validity is well known and adequate (Brown and Adams 1992; Revicki et al. 1994).

The sociodemographic variables included: age in years, sex, race, education, income level in dollars, insurance, marital status, and employment status. Information regarding employment status was attained by asking respondents what they were doing during most of the previous week (as in the labor force surveys). Insurance refers to private or publicly assisted forms of payment for health care services. Private forms of insurance include health insurance plans paying part or all doctor bills, health maintenance organizations (HMOs), and prepaid group practice plans. Publicly assisted medical assistance or other public programs such as welfare or public assistance forms of health care as well as Medicare from Social Security were also considered.

Questions on chronic health conditions were drawn from the Health Interview Survey. Respondents were queried as to whether they were currently experiencing specific physical health conditions. These included asthma, high sugar or diabetes, heart trouble, high blood pressure, arthritis or rheumatism, trouble breathing, a stroke and/or cancer.

Data analysis

Unlike simple random sampling, in which respondents have equal probabilities of selection, the multistage sampling procedures of the East Baltimore Epidemiologic Catchment Area survey lead to un- equal probabilities of selection. Therefore, a weight was assigned to each respondent based on his or her selection probability and weighted data are used in our analyses and reported in the text and tables. Results based on weighted data can thus be generalized to the East Baltimore community. The weighting procedure adopted here- in also adjusts variance estimates for the clustered aspect of the sampling so that tests of significance are conservative (Kessler et aI. 1985; Leaf et al. 1991).

As the number of disability days was highly skew, analyses were performed using logistic regression, with the presence or absence of disability days as the dependent variable (Cleary and Angel 1984; Fleiss et al. 1986). In the first stage of the logistic regression a multi- variate sociodemographic model was created for disability days. Variables were retained if the estimates were significant or if their inclusion substantially changed the magnitude of coefficients for other terms. In the second stage of modeling, psychiatric variables were added to the best fitting sociodemographic model. There was one regression equation for each psychiatric disorder. Dis- ability days associated with six psychiatric disorders and the presence of high distress were each compared to the values for respondents without that specific DIS/DSM-III diagnosis (Boyd et al. 1984).

Results

T h e s a m p l e in E a s t B a l t i m o r e is a b o u t 6 3 % female ( T a b l e 1). W h i l e the l a rges t age g r o u p c o m p r i s e s y o u n g a d u l t s u n d e r 30 yea r s of age ( 2 8 % , n = 777), t he difference b e t w e e n th is a n d the s m a l l e s t g r o u p s , t hose be- t w e e n 30 a n d 64 yea r s old, is o n l y 4 % , O n e - t h i r d a re A f r i c a n - A m e r i c a n ( 3 5 % , n = 958) a n d 4 0 % (n = 1124) a re m a r r i e d . O n l y o n e - t h i r d e a r n $20 ,000 or m o r e a year , w i t h 4 5 % (n = 1165) l i v ing in p o v e r t y o r !ow- i n c o m e levels. F u l l - t i m e e m p l o y e d w o r k e r s c o m p r i s e less t h a n o n e - h a l f ( 44%, n = 1205) of the s amp le . E i g h t y - t h r e e p e r c e n t (n = 2288) h a v e p r i v a t e o r p u b l i c h e a l t h i n s u r a n c e . T h i r t y - e i g h t p e r c e n t (n = 1048) ex- p e r i e n c e d at l eas t 1 d i s a b i l i t y d a y a t b a s e l i n e a n d 4 5 % (n = 1259) h a v e o n e o r m o r e c h r o n i c diseases .

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Table 1 Description of Baltimore Epidemiologic Catchment Area Sample ~

n %

Sex Male 1,027 37 Female L741 63

Age (years) 18-29 777 28 30-44 655 24 45-64 659 24 65 + 713 26

Education Eighth grade or less 737 27 Ninth to eleventh grade 694 25 High school 799 29 Beyond high school 538 19

Race African American 958 65 White and other 1,810 35

Marital status Married 1,644 60 Not married 1,124 40

Health insurance Insurance 2,288 83 No insurance 480 17

Income Under $4,999 444 16 $5,000 12,499 721 29 $12,500-19,999 475 19 $20,000 + 825 34

Employment Full-time 1,205 44 Not full-time 1,557 56

Chronic diseases One or more 1,259 45 None 1,509 54

Disability None 1,712 62 One or more 1,048 38

"The total sample consists of 2768 individuals. Data were required to be complete for age, sex, and race. For other variables the total does not always equal 2768 because of missing data

There is no striking variation in the percentage of respondents with disability days in the population according to sociodemographic variables (Table 2). Per- sons with disabilities at baseline were most likely (52%) to have a disability day at follow-up. Those with more than a high school education reported the second highest rate of absences (43%). The aging and persons with no prior disability days had the lowest absences at 31%. The crude odds differed trivially from the adjusted relative odds. The odds of having a disability day, adjusting for all the personal characteristics and chronic physical conditions, are presented in the far right column. Persons with 1 or more disability day at baseline had the greatest odds of having a disability

day, with odds 2.2 (95% CI = 1.69, 2.90) times greater than those with no prior disability. African-Americans and those with less than a high school education experienced the lowest odds of missing work or other activities.

The percentage of those with at aleast 1 disability day at wave 2 by type of psychopathology, the number of persons with each disorder according to our temporal classification, and the adjusted odds of having a disability day for each psychiatric disorder are considered in Table 3. Each of eight main rows contains a separate model controlling for sociodemographic fac- tors, chronic medical condition, and temporal characteristics of that particular disorder (onset, remission, and chronicity). The psychiatric disorders include major depressive disorder, alcohol abuse and dependence, other drug abuse/dependence, panic disorder, obsessive-compulsive disorder, and phobic disorder. Categories of high distress scores, and those with any DIS/DSM-III disorder, were also included. Per- sons with no DIS/DSM-III disorder were the compari- son group for those in any DIS/DSM-III disorder group.

The 19 subjects with chronic DIS/DSM-III panic disorders had the largest percentage reporting a disability day (100%), closely followed by the 14 subjects with chronic major depression, with 90% disability days and those with chronic high distress at 77%. Only 28% of those experiencing incidence of alcohol abuse or dependence reported at least one disability day.

The adjusted association of type of psychopathology on disability days appears in the far right column of Table 9. Subjects experiencing new occurrence or onset of a panic disorder had the greatest adjusted odds of missing work (OR = 7.3, 95%CI = 1.84, 28.69). This was followed by subjects experiencing a chronic major depressive disorder, with an odds ratio of 7.2 (95%CI = 0.33, 160.62), although this did not reach conventional levels of significance. Large confidence intervals caution us regarding the possible stability of these findings. The chronic distress group had relative odds of 5.0 (95%CI = 2.83, 6.30). The lowest odds of having a disability day were for subjects with onset of alcohol abuse or dependence (0.6 OR, 95%CI = 0.24, 1.31), although this was not significant.

The results of temporal changes in psychopathology for the three strongest categories (panic, depression, and high distress) reflect levels of disability that might be expected, for the most part (Fig. 1). For example, the percentage with disability days rises for those with incident panic and high distress and falls for those with remission of panic and distress. Levels are high and remain high for both chronic panic and high distress, and are lowest for those who do not have panic or high distress on either wave. This pattern for absence of disorder at both waves, and for chronic disorder, is what is displayed for depression; but there appears to be no difference in disability for those having a new

Table 2 Significant predictors of disability days at wave 2 (n = 2619)

Percentage in sample with Crude odds of Adjusted odds of having disability days having disability days disability days

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Sex Male 34 1.00 1.00 Female 43 1.43 1.39 (1.07, 1.82)

Age (years) 18-29 41 1.14 1.87 (1.15, 3.05) 30-44 42 1.17 1.81 (1.12, 2.93) 45 64 39 1.00 1.55 (1.01, 2.38) 65 + 31 1.00 1.00

Education Eighth grade or less 34 0.79 0.63 (0.41, 0.98) Ninth to eleventh grade 38 0.93 0.69 (0.47, 1.02) High school 38 0.97 0.67 (0.47, 0.96) Beyond high school 46 1.00 1.00

Race African American 32 0.68 0.60 (0.43, 0.85) White and other 41 1.00 1.00

Chronic physical condition One or more 43 1.34 1.59 (1.t7, 2.16) None 36 1.00 1.00

Disability days at wave 1 One or more 52 2.38 2.23 (1.69,2.90) None 31 1.00 1.00

Table 3 Disability days at follow-up and temporal patterns of psychopathology for 2619 subjects (DIS/DSM-III National Institute of Mental Health Diagnostic Interview Schedule scored to reflect DSM-III diagnoses, GHO General Health Questionnaire)

Type of Psychopathology a Percentage with 1 + No. with Adjusted 95% confidence disability days ~ psychopathology odds ratio a interval

DIS/DSM-III Major depressive disorder

DIS/DSM-III Alcohol abuse/dependence

DIS/DSM-III Drug abuse/dependence

DIS/DSM-III Panic disorder

DIS/DSM-III Obsessive-compulsive disorder

DIS/DSM-III Phobic disorder

Any DIS/DSM-III disorder

High GHQ score b

Onset Remission Chronic








66 27 2.4 (0.55, 10.50) 63 68 2.4 (0.96, 6.21) 90 14 7.2 (0.33,160.62)

28 57 0.6 (0.24, 1.31) 48 73 1.5 (0.70, 3.05) 48 71 1.5 (0.72, 3.14)

48 29 1.4 (0.48, 4.24) 46 52 1.4 (0.54, 3.85) 50 14 1.4 (0.25, 7.83)

71 32 7.3 (1.84, 28.69) 61 67 0.8 (0.31, 2.03) 100 19 1.0 (0.23, 4.45)

60 39 2.0 (0.68, 6.16) 45 44 1.1 (0.40, 2.88) 64 16 2.1 (0.32, 13.8)

49 112 1.6 (0.81, 3.04) 49 345 1.4 (0.95, 2.16) 48 111 1.3 (0.66, 2.51)

46 218 1.1 (0.66,1.80) 38 446 1.4 (0.98, 2.06) 38 313 2.0 (1.28, 2.96)

59 196 2.6 (1.58, 4.46) 45 274 1.3 (0.83, 2.04) 77 144 5.0 (2.56, 9.90)

a In prior 6 months b In prior several weeks ~ In prior 3 months d Adjusted for sex, age, education, race, chronic physical condition, and disability days at wave t

384

Fig. 1 Mean disability days and temporal patterns of psychopathology. �9 Absence; + onset; �9 remission; �9 chronic

DIS/DSM-III Major Depresive Disorder

MEAN DISABILITY DAYS 12

O.B l

0.6

0 4

0 2 I

L BASELINE 1 YEAR FOLLOW UR

DISIDSM-III Panic Disorder MEAN DISABILITY DAYS

1

0.8

0.6

0,4

0.2

12

1

0.8

06

0.2

O

High GHQ Distress

MEAN DISABILITY DAYS

BASELINE 1 YEAR FOLLOW UF~ BASELINE 1 YEAR FOLLOW DR

onset versus a remission, these being in between the chronic and absent groups. It may be that depressive symptomatology undulates too slowly for onset and remission to have a strong effect within the passage of 1 year's time.

Depression had a stronger effect than chronic physical condition on disability days. For example, the odds ratio for chronic physical condition was 1.59, smaller than the odds ratios in Table 3 (2.4, 2.4, 7.2).

In order to examine robustness of findings, addi- tional models were examined. To test whether the inclusion of any specific physical condition changed the pattern of results, each individual physical condition was entered into the regression equations. The largest associations were found for subjects suffering from stroke (OR = 2.6, 95%CI = 0.92, 2.81) or diabetes (OR = 2.3, 95%CI = 0.26, 1.57). These did not exceed the odds for psychiatric disorders in the respective models. Also, separate analyses were conducted without chronic physical condition in the regression equation, and the effects of depression on disability remained unchanged. Separate analyses of Tables 2 and 3 were also repeated for four subgroups (those employed full time in the labor force, full time homemakers, women, and men). The overall strength and direction of findings of the relationships were similar to those of the total sample.

Discussion

In both cross-sectional and longitudinal analyses, and for emotional and general disability days, mental disorders had the strongest association with missing days from work, school, or one's usual activities. This was

true after statistical adjustment for known sociodemographic variables, prior disability, and physical condition.

We categorized temporal change in psychiatric disorders as onset, remission, or chronic. Our findings indicate a pervasive link between chronic disorders and disabilities, except in the case of panic disorders, where onset proved a greater predictor for absence from work or usual activities. Persons experiencing onset of panic attacks for the first time may be prompted by the fear of myocardial infarction to seek medical care and/or avoid strenuous activities, thus experiencing disability. Panic disorder has been found to be the most common DIS diagnosis for which people seek treatment (Boyd 1986). Respondents with a chronic panic disorder may feel less danger and thus be less prone to call a phy- sician. Ours is essentially a 2-wave longitudinal design, by which causality may be inferred rather than perfect- ly established; thus, our analysis shows how disability and psychopathology evolve together over time. None- theless, the longitudinal data allow a more cogent analysis of causal relationship than has been possible in prior research.

Alcohol, drug; and mental (ADM) disorders are major causes of morbidity, disability, and mortality. Ac- cording to one report, the costs of depression approx- imate those for heart disease (Greenberg et al. 1993; Stoudemire et al. 1986). The economic burden of ADM disorders in the United States, whether measured in direct costs (diagnoses and treatment of patients) or indirect costs (reduced earnings due to lost productivity, premature death, and other related costs) (Bartel and Taubman 1986; Barth 1990; Frank and Gertler 1987; Mullaky and Sindelar 1994; Rice et al. 1990), is staggering: estimates for 1985 were $273.3 bil- lion (Richardson 1994). For depression, the annual

385

e c o n o m i c b u r d e n for 1990 has been e s t i m a t e d at $44 b i l l i on ( G r e e n b e r g et al. 1993). Yet h u m a n suffer ing a n d the d i m i n i s h e d qua l i t y of life a s s o c i a t e d wi th i l lness defy such " h u m a n cap i t a l cos t s " m o d e s of m e a s u r e - ment . P r e v e n t i o n a n d t r e a t m e n t efforts s h o u l d e m b r a c e c lose r sc reen ing a n d su rve i l l ance in p r i m a r y ca re a n d e d u c a t i o n a l a n d w o r k a d j u s t m e n t s for the e m o t i o n a l l y d i sab led as are p l anned for o ther g roups with disabilities.

Acknowledgements This analysis was supported by National Insti- tute of Mental Health (NIMH) grant MH 47447 and MH 14592.

Thomas Grein, MD, MPH, provided technical assistance with the data. We thank the editor and two anonymous reviewers for their criticisms.

The ECA Program is a series of five epidemiologic research studies performed by independent research teams in collaboration with staff of the division of Biometry and Epidemiology (DBE) of the NIMH. During the period of data collection, the ECA program was supported by cooperative agreements. The NIMH Principal Collaborators were Darrel A. Regier, MD, Ben Z. Locke, MSPH, William W. Eaton, PhD (October 1 1978, through October 1 1983), and Jack Burke, MD (October 1 1983, through March 1 1987). The NIMH Project Officers were Carl A. Taube, PhD, and William Huber. The Principal Investigators and Co-investigators from the five sites were: Jerome K. Myers, PhD, Myrna M. Weissman, PhD, and Gary L. Tischler, MD, Yale University, New Haven, CT (U01 MH 33870); Morton Kramer, ScD, Ernesl Gruenberg, MD, DPH and Sam Shapiro, MS, Johns Hopkins University, Baltimore, MD (U01 MH 33870); Lee N. Robins, PhD, and John Helzer, MD, Washington University, St. Louis, M. (U01 MH 33883); Dan Blazer, MD, and Linda George, PhD, Duke University, Durham, N.C. (U01 MH 35386); and Marvin Karno, MD, Richard L. Hough, PhD, Javier I. Escobar, MD, M. Audrey Burnam, PhD, and Diane Timbers, PhD, University of California at Los Angeles (U01 MH 35865).

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Psychopathology and the development of disability