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A systematic review of randomised control trials on the effects of yoga

on stress measures and mood

Michaela C Pascoe a Isabelle E Bauer b

a Institute of Neuroscience and Physiology Dept of Clinical Neuroscience and Rehabilitation Sahlgrenska Academy at University of Gothenburg Swedenb University of Texas Health Science Center Department of Psychiatry and Behavioral Science Houston TX USA

a r t i c l e i n f o

Article history

Received 12 February 2015

Received in revised form

10 July 2015

Accepted 10 July 2015

Keywords

Yoga

Anxiety

Depression

Mood

Stress

Brain imaging

In1047298ammation

Exercise

a b s t r a c t

Stress related disorders such as depression and anxiety are leading sources of disability worldwide and

current treatment methods such as conventional antidepressant medications are not bene1047297cial for all

individuals There is evidence that yoga has mood-enhancing properties possibly related to its inhibitory

effects on physiological stress and in1047298ammation which are frequently associated with affective disor-

ders However the biological mechanisms via which yoga exerts its therapeutic mood-modulating effects

are largely unknown This systematic review investigates the effects of yoga on sympathetic nervous

system and hypothalamic pituitary adrenal axis regulation measures It focuses on studies collecting

physiological parameters such as blood pressure heart rate cortisol peripheral cytokine expression and

or structural and functional brain measures in regions involved in stress and mood regulation Overall

the 25 randomised control studies discussed provide preliminary evidence to suggest that yoga practice

leads to better regulation of the sympathetic nervous system and hypothalamic-pituitary-adrenal sys-

tem as well as a decrease in depressive and anxious symptoms in a range of populations Further

research is warranted to con1047297rm these preliminary 1047297ndings and facilitate implementation in clinical

settings

copy 2015 Elsevier Ltd All rights reserved

1 Introduction

11 Mood stress and brain changes

Unipolar depression and anxiety are the leading source of adult

disability worldwide (Shyn and Hamilton 2010 Whiteford et al

2013) Approximately 350 million people are estimated to suffer

from depression (World Health Organisation [WHO] 2013) and

associated societal costs are V92 billion in Europe alone (Wittchen

et al 2011 Gustavsson et al 2011 Olesen et al 2012) Depressionand anxiety are highly co-morbid with each other and have shared

aetiology and neurobiology (Neale and Kendler 1995) Anxiety is the

single strongest predictor of depression onset (Mathew et al 2011

Avenevoli et al 2001 Hranov 2007) While there are neurochem-

ical differences between the conditions recent studies view

depression and anxiety as overlapping syndromes existing on a

continuum (Hranov 2007 Baldwin et al 2002 Ionescu et al 2013)

Depression and anxiety are closely linked to structural and

functional abnormalities in a number of stress and mood related

brain regions (Drevets 1998 Davidson 2003 Siegle et al 2002

Abercrombie et al 1998 Drevets 1999 Eren et al 2003) Alter-

ations have been observed in the anterior cingulate cortex (ACC)

(involved in immune response (Capuron et al 2005 Craig 2003

Goehler et al 2000 Gaykema and Goehler 2011) affective regu-

lation and reward anticipation ( Jackson et al 2006 Decety and Jackson 2004)) and the prefrontal cortex (PFC) (which anatomi-

cally connects to the ACC and is involved in social behaviour and

personality traits (Miller et al 2002 Yang and Raine 2009))

Functional and structural changes are also seen in regions of the

limbic system (involved in the stress response regulations of fear

anxiety mood and emotion (Herman et al 2005 Kempton et al

2011 Davis 1992)) namely the hippocampus and amygdala

Men with a 1047297rst-episode major depression show smaller hip-

pocampal total and gray matter volumes than healthy men ( Frodl

et al 2002) In monozygotic twins a smaller hippocampal volume

has been found to be a risk factor for the development of

Corresponding author Institute of Neuroscience and Physiology Dept of Clin-

ical Neuroscience and Rehabilitation Sahlgrenska Academy at University of Goth-

enburg Box 440 SE-405 30 Gothenburg Sweden

E-mail address michaelapascoeneuroguse (MC Pascoe)

Contents lists available at ScienceDirect

Journal of Psychiatric Research

j o u r n a l h o m e p a g e w w w e l s e v i e r c om l o c a t e p s y c h i r e s

httpdxdoiorg101016jjpsychires201507013

0022-3956copy

2015 Elsevier Ltd All rights reserved

Journal of Psychiatric Research 68 (2015) 270e282



posttraumatic stress disorder Additionally recent models of neu-

roprogression suggest that the hippocampal atrophy observed in

unipolar depression is cumulative as the degree of atrophy appears

to be related to the number of untreated episodes and illness

duration (Sheline et al 2003 Berk et al 2011 Fries et al 2012)

One could therefore argue that the relationship between structural

brain abnormalities and affective disorders is bidirectional

The aetiology of depressive and anxious disorders are complex

and polygenetic and additional to structural abnormalities in-

dividuals show abnormalities in the function and expression of

monoamine neurotransmitters such as serotonin and dopamine

(Krishnan and Nestler 2008 Morilak and Frazer 2004) increased

oxidative stress (Michel et al 2012 Bouayed et al 2009) decreased

expression of the neurotropic protein brain-derived neurotrophic

factor (BDNF) (Autry and Monteggia 2012) and changes in the

expression of cytokines (Dantzer 2012) Cytokines are small cell

signalling protein molecules essential in the innate immune

response and in1047298ammation Cytokines can be either pro or anti-

in1047298ammatory (del Zoppo et al 2000) and among other functions

stimulate the autonomic nervous system (ANS) and the hypotha-

lamic pituitary adrenal (HPA) axis (Silverman and Sternberg 2012)

The ANS has two main divisions the parasympathetic nervous

system (PNS) and the sympathetic nervous system (SNS) TheSNS isinvolved in the mobilisation of the body in situations of stress to

either lsquo1047297ght or 1047298ightrsquo the stressor The PNS is responsible for

returning the body to a homoeostatic state after the activation of

the SNS (Buijs 2013) In many cases the PNS and SNS have com-

plementary and opposing actions in that one system is responsible

for activating a physiological response and the other is responsible

for inhibiting it (Buijs 2013) Activation of the SNS is associated

with a number of physiological changes including increased heart

rate blood pressure HPA axis activation and subsequent down-

stream release of the glucocorticoid hormone cortisol from the

adrenal cortex (Raison et al 2006) Glucocorticoid levels and the

further synthesis of pro-in1047298ammatory cytokines are normally

regulated by a HPA axis negative feedback mechanism (Silverman

and Sternberg 2012)The reciprocal relationship among stress HPA axis regulation

and depression and anxiety is well known (Dantzer 2012 Dantzer

et al 2008 Maes 2008a) Clinical depression and anxiety are

associated with an increased in1047298ammatory state These conditions

are characterized by dysfunctional glucocorticoid feedback inhibi-

tion (Silverman and Sternberg 2012) hypersecretion of CRH HPA

axis dysfunction (Boyer 2000 Roy-Byrne et al 1986) increased

circulatory cortisol (a widely used biomarker of HPA axis dysfunc-

tion) (Olson et al 2012) and production of pro-in1047298ammatory cy-

tokines (Silverman and Sternberg 2012 Raison et al 2006

Sapolsky et al 2000 King and Hegadoren 2002) Anxiety related

sustained central arousal has been proposed to deplete neuro-

transmission in the forebrain and thus precipitate the onset of

depression (Neale and Kendler 1995 Eison 1990 Johnson et al1990 Nutt et al 1998 Schulberg et al 1998)

On the other hand chronic stress and in1047298ammation can

contribute to the onset of depressive and anxious symptoms

(Dantzer 2012 Masi and Brovedani 2011 Pascoe et al 2011)

Treatment with the in1047298ammatory cytokine Interferon-a (INF-a)

(Capuron and Miller 2004) has been associated with the presen-

tation of depressive and anxious symptoms in cancer survivorships

(Capuron et al 2002) These depressive symptoms resolve with

INF-a therapy termination (Capuron and Dantzer 2003) and anti-

depressant medication (Musselman et al 2001)

Finally the bene1047297cial effects of pharmaceutical antidepressant

medications appear to relate to their in1047298uence on in1047298ammatory

activity Tricyclic antidepressant medications reduce pro-

in1047298

ammatory Interleukin-1 (IL-1) and Interleukin-2 (IL-2) and

increase anti-in1047298ammatory Interleukin-10 in animal models

(Kubera et al 2000) suggesting that these pharmaceutical anti-

depressant medications likely reduce depressive symptoms at

least in part by mediating mood modulating in1047298ammatory

markers (Kubera et al 2000) Additionally high basal in1047298amma-

tion is associated with a treatment resistance to pharmaceutical

anti-depressant interventions in clinical populations An

increased in1047298ammatory state as characterised by heightened

plasma concentrations of in1047298ammatory cytokines and acute phase

proteins prior to antidepressant treatment is associated with a

non-response (Maes 2008b Raison et al 2013)

Not only are current pharmacological treatment methods such

as selective serotonin reuptake inhibitors (SSRI) not bene1047297cial for

all individuals (Howland 2006 Kirsch et al 2008) these medica-

tions are associated with deleterious side effects such as metabolic

disorders and diabetes (McIntyre et al 2010) that reduce quality of

life and negatively in1047298uence individual adherence to the medica-

tion (Schatzberg 2007) Thus there is need for safer and more

effective treatment methods for mood disorders

12 Yoga is an effective treatment for depressive and anxious

symptomatology

The termyogais Sanskrit for lsquounionrsquo or lsquoto yokersquo and describes a

lifestyle aiming to achieve union of mind body and spirit While the

origins of yoga are unclear the Indian sage Patanjali described eight

limbs of yoga (G F 1998) which have been performed in Eastern

cultures for thousands of years In recent years yoga has become

increasingly popular in Western cultures (Ding and Stamatakis

2014 Tindle et al 2005) There are many forms of yoga each

with unique approaches and theoretical underpinnings making a

de1047297nitive taxonomy dif 1047297cult (Ospina et al 2007) Previous authors

have noted that this lack of a de1047297nitive de1047297nition and subsequent

differences in the forms studied has hampered neuroscienti1047297c

research in this 1047297eld (Lutz et al 2007) All forms of yoga however

share common elements including use of controlled breathing

(pranayama) physical postures (asanas) and meditative techniques(dhyana) to achieve well-being and mind body union and balance

(Farmer 2012 P1047298ueger 2011 Travis and Pearson 2000) Several

studies and systematic reviews demonstrate the mood enhancing

effects of yoga as treatments for clinical depression ( Uebelacker

et al 2010 Pilkington et al 2005 DSilva et al 2012

Balasubramaniam et al 2012) and anxiety (Chattha et al 2008

Granath et al 2006 Banerjee et al 2007 Harinath et al 2004

Kjellgren et al 2007 West et al 2004 Woolery et al 2004

Smith et al 2007 Li and Goldsmith 2012) Yoga practice is asso-

ciated with a reduced number of major depressive episodes and

lower risk for dysthymia which is a milder but longer-term form of

depression (Banerjee et al 2007 Kjellgren et al 2007 Woolery

et al 2004 John et al 2007 Sharma et al 2006 Butler et al

2008) Meta-analyses and systemic reviews indicate that yogaand meditative therapies are equally effective as conventional an-

tidepressants in the treatment of depressive and anxious disorders

(da Silva et al 2009 Cramer et al 2013 Chen et al 2012) The

limited data thus far suggests that these practices are associated

with changes in the stress response (Kinser et al 2012 McCall

2013) The neurobiological mechanisms however via which yoga

exerts its mood enhancing effects are still not clearly understood

2 Methods

21 Systematic search strategy

In the present study we aimed to systematically review rand-

omised control trials (RCTs) investigating the effects of yoga on

MC Pascoe IE Bauer Journal of Psychiatric Research 68 (2015) 270e 282 271



stress-related biological measures and their neural correlates in

the context of depressive and anxious symptomology We searched

Pubmed MedlineOvid and Scopus with no year restriction for ar-

ticles containing the speci1047297c title word lsquoyogarsquo and the speci1047297c

abstract word lsquodepression rsquo lsquomoodrsquo lsquoanxietyrsquo lsquodepressive rsquo lsquoaffectiversquo

or lsquoanxiousrsquo and lsquoimmunersquo lsquocortisolrsquo lsquocatecholaminesrsquo lsquonorepi-

nephrinersquo lsquocytokinersquo lsquointerleukinrsquo lsquoInterferonrsquo lsquotumour necrosis

factor-alpharsquo lsquobrain-derived neurotropic factorrsquo lsquodopaminersquo lsquosero-

toninrsquo lsquoblood pressurersquo or lsquoheart ratersquo To explore the neural cor-

relates of stress in relation with yoga we searched the speci1047297c

abstract word lsquobrainrsquo and with the speci1047297c abstract words lsquomag-

netic resonance imaging (MRI)rsquo lsquofunctional MRIrsquo lsquodiffusion tensor

imaging (DTI)rsquo lsquoEEGrsquo lsquospectroscopyrsquo lsquoresting state fMRIrsquo lsquomagnetic

resonance spectroscopy (MRS)rsquo lsquopositron emission tomography

(PET)rsquo or lsquoarterial spin labelling (ASL)rsquo Articles reviewed were

restricted to original RCTs published in English that included a

population who engaged in a yoga practice with outcome mea-

sures related to HPA axis activation in1047298ammation or brain imaging

in conjunction with a measure of mood or current affective state

Review papers non-randomised trials case series and disserta-

tions were excluded

3 Results

A total of 122 papers with stress-related physiological parame-

ters were initially retrieved Studies were screened using title and

abstract when required full texts were accessed (n frac14 76) Nine of

these were excluded as they were review articles A further 31

papers were excluded as they were quasi-experimental cross

sectional of cohort studies four were excluded as they did not

include a biological and mood related outcome and 1047297ve were

excluded as they did not involve a yoga based intervention Three

additional papers were excluded as their results have not yet been

published Thus 24 RCT trials were included in the1047297nal review The

details of the search strategy are depicted in Fig 1

A total of 50 brain imaging papers were initially retrieved 34

were duplicates and were removed a further four were reviews

leaving 12 articles that were screened for eligibility seven were

removed as they did not include a brain imaging outcome one was

removed as it did not include a yoga asana intervention Three

further articles were removed as they were not RCTs Thus one RCT

trial was included in the 1047297nal review The details of the search

strategy are depicted in Fig 2

31 Characteristics of the included trials

Reviewed study characteristics are outlined in Table 1 Twenty-

1047297ve RCTs examining the effects of yoga on biological outcomes in

conjunction with mood related or brain related measures have

been included in this review Eight RCTs originated from India

(Sujatha and J A 2014 McDermott et al 2014 Kanojia et al 2013Ebnezar et al 2012 Gopal et al 2011 Telles et al 2010 Vadiraja

et al 2009 Malathi et al 1998) nine from the United States

(Woolery et al 2004 Corey et al 2014 Chandwani et al 2014

Kiecolt-Glaser et al 2014 Field et al 2013 Innes and Selfe

2012 Banasik et al 2011 Streeter et al 2010a) two from Australia

(Smith et al 2007 Cheema et al 2013) two from the United

Kingdom (Newham et al 2014 Bowden et al 2012) one from

Fig 1 Flow chart showing the retrieval process of biological related trials included in the systematic review

MC Pascoe IE Bauer Journal of Psychiatric Research 68 (2015) 270e 282272



Germany (Sarubin et al 2014)onefrom Spain (Tolbanos Roche and

Mas Hesse 2014) one from Sweden (Hallgren et al 2014) and two

from Brazil (Danucalov et al 2013 Rocha et al 2012)

The studied populations were heterogeneous across trials three

involved individuals with depression (Woolery et al 2004 Fieldet al 2013 Sarubin et al 2014) one focused on healthy in-

dividuals experiencing mildmoderate stress (Smith et al 2007)

one studied individuals with alcohol dependence (Hallgren et al

2014) and one involved 1047298ood survivors (Telles et al 2010) Four

studied people with illnesses commonly comorbid to mood disor-

ders such as metabolic problems (McDermott et al 2014 Corey

et al 2014) and hypertension (Sujatha and J A 2014 Tolbanos

Roche and Mas Hesse 2014) Six trials focused on individuals

with medical conditions such as restless leg syndrome (Innes and

Selfe 2012) cancer survivorships (Vadiraja et al 2009

Chandwani et al 2014 Kiecolt-Glaser et al 2014 Banasik et al

2011) and osteoarthritis (Ebnezar et al 2012) One study involved

healthy military personal (Rocha et al 2012) Finally eight studies

involved healthy adults (Kanojia et al 2013 Gopal et al 2011Malathi et al 1998 Streeter et al 2010a Cheema et al 2013

Newham et al 2014 Bowden et al 2012) including familial

caregivers (Danucalov et al 2013)

Hatha yoga was the most common intervention and was used in

six trials (Smith et al 2007 Sujatha and J A 2014 Kiecolt-Glaser

et al 2014 Cheema et al 2013 Sarubin et al 2014 Danucalov

et al 2013) Iyengar yoga was the second most common inter-

vention and was used in 1047297ve trials (Woolery et al 2004 Innes and

Selfe 2012 Banasik et al 2011 Streeter et al 2010a Bowden et al

2012) while two trials used prenatal yoga (Field et al 2013

Newham et al 2014) One trial used restorative yoga (Corey et al

2014) one used Patanjali yoga (Telles et al 2010) four did not

specify the yoga form yet provided the sequence in the method-

ology (McDermott et al 2014 Kanojia et al 2013 Ebnezar et al

2012 Chandwani et al 2014) and six did not specify the yoga

form or clearly outline the sequence used (Gopal et al 2011

Vadiraja et al 2009 Malathi et al 1998 Tolbanos Roche and

Mas Hesse 2014 Hallgren et al 2014 Rocha et al 2012)

The most common stress-related biological measures (n frac14 11studies) were autonomic arousal measures including blood pres-

sure heartrate skinconductanceand respiration (Smithet al 2007

Sujatha and J A 2014 McDermott et al 2014 Kanojia et al 2013

Ebnezar et al 2012 Gopal et al 2011 Telles et al 2010 Innes

and Selfe 2012 Tolbanos Roche and Mas Hesse 2014 Yeung et al

2014 Cheema et al 2013) Heart rate variability (HRV) was

measured in two studies as an indicator of ANS function and car-

diovascular response (Telles et al 2010 Cheema et al 2013)

increased HRV is interpreted to indicate greater parasympathetic

nervous system activity and a healthy balance between the sym-

pathetic and parasympathetic nervous systems (Buijs 2013)

The steroid hormone cortisol was assessed in 13 trials (Woolery

et al 2004 Gopal et al 2011 Vadiraja et al 2009 Corey et al

2014 Chandwani et al 2014 Field et al 2013 Banasik et al2011 Newham et al 2014 Bowden et al 2012 Sarubin et al

2014 Hallgren et al 2014 Danucalov et al 2013 Rocha et al

2012) Cytokines were measured in two trials (Gopal et al 2011

Kiecolt-Glaser et al 2014) Some other relevant health related

measures included lipid pro1047297les and body mass index (Sujatha and

J A 2014 McDermott et al 2014) As outlined in Table 1 all trials

included some measure of depressive symptoms except Sujatha

et al Smith et al Malathi et al and Ebnezar et al (Smith et al

2007 Sujatha and J A 2014 Ebnezar et al 2012 Malathi et al

1998) and 16 studies included a measure of anxiety (Woolery

et al 2004 Smith et al 2007 Sujatha and J A 2014 Ebnezar

et al 2012 Gopal et al 2011 Telles et al 2010 Vadiraja et al

2009 Field et al 2013 Innes and Selfe 2012 Streeter et al

2010a Cheema et al 2013 Newham et al 2014 Tolbanos Roche

Fig 2 Flow chart showing the retrieval process of imaging related trials included in the systematic review










and Mas Hesse 2014 Hallgren et al 2014 Danucalov et al 2013

Rocha et al 2012) Other studied measures included quality of life

(Smith et al 2007 Chandwani et al 2014 Kiecolt-Glaser et al

2014 Cheema et al 2013) stress or perceived stress (Sujatha and J

A 2014 McDermott et al 2014 Vadiraja et al 2009 Corey et al

2014 Innes and Selfe 2012 Hallgren et al 2014 Danucalov

et al 2013 Rocha et al 2012) fatigue and sleep quality (Telles

et al 2010 Chandwani et al 2014 Kiecolt-Glaser et al 2014

Innes and Selfe 2012 Bowden et al 2012) and pain or disability

(Smith et al 2007 Ebnezar et al 2012 Banasik et al 2011)

32 Findings of the included trials

321 Cortisol outcomes

Many of the reviewed studies assessed salivary cortisol There

are some limitations associated with salivary cortisol measure-

ments that can affect the reliability of the outcome Various drugs

and medications including caffeine pharmaceutical anti-

depressants and over-the-counter hydrocortisone creams affect

cortisol levels (Poll et al 2007 Granger et al 2009) as well as

smoking (Badrick et al 2007) and blood in the saliva (Ashman

et al 2002) Eating and drinking substances with low pH can

arti1047297cially increase cortisol levels (Goodyer et al 1996) and homecollection can be associated with compliance issues deviation from

instructions as well as insuf 1047297cient provision of saliva (Weibel

2003) Thus in clinical research it is important to ensure that

salivary measures are taken at several repeated measures over the

course of several days at the same time intervals Additionally as

cortisol levels follow a circadian rhythm the time of day that

cortisol sampling occurs should be held constant across the inter-

vention Controlling for waking time when assessing the cortisol

awakening response (CAR) (which is characterised by a rise in

cortisol upon awakening generally reaching its peak during the

initial 30e45 min after waking (Clow et al 2004)) is also important

(Clow et al 2004) Early waking time has been associated with

heightened CAR (Kudielka and Kirschbaum 2003) Thus waking

time should be documented and explored as a possible confound-ing factor The above collection conditions were satis1047297ed in most of

the reviewed studies as shown in Table 1 Those studies that did not

satisfy the above discussed collection standards of salivary cortisol

are discussed below where relevant

322 Salivary cortisol before and following yoga classes

Only two studies measured salivary cortisol before and

following yoga classes Newham et al found that eight weeks of

prenatal yoga was associated with decreased salivary cortisol state

anxiety and pregnancy speci1047297c anxiety in healthy women

compared to treatment as usual both after the 1047297rst yoga class and

after the 1047297nal yoga class (Newham et al 2014) Similarly in a trial

by Field et al involving 96 women with prenatal depression one

session of prenatal yoga was seen to decrease depression anxietyanger and pain After 12 weeks of yoga decreases were also

observed in cortisol estriol and progesterone Effects were also

seen after 12 weeks of a social support group suggesting a role of

social support in mediating HPA activity (Field et al 2013) The

authors state that the time of cortisol estriol and progesterone

sampling was held constant across the yoga intervention as sam-

ples were taken at mid morning both pre and post intervention

(Field et al 2013) Thus these two studies indicate that yoga

practice appears to have an immediate bene1047297cial effect on cortisol

levels

323 Daytime cortisol

Two studies measured daytime cortisol Bowden et al tested

fasting (2 h) salivary cortisol in healthy adults and found that

Iyenger yoga Brain Wave Vibration (a meditation practised in a

class involving rhythmic movements of the head neck and body)

and mindfulness classes were not associated with a change in

cortisol All interventions however improved mindfulness and

decreasedmeasures of stress A limitation of this study is that saliva

samples for cortisol testing were collected between 11am and 3pm

so the exact time of collection was not held constant between all

participants The authors highlighted however that cortisol levels

are relatively stable between these times that two separate sam-

ples from each individual were taken at each time point and that

pre-post intervention collection times for each individuals were

matched (Bowden et al 2012)

Banasik et al found that eight weeks of Iyengar yoga practice

was associated with lower salivary cortisol collected at 1047297ve pm

among breast cancer survivors (Banasik et al 2011) These authors

however did not specify if participants were fasting or not before

cortisol collection and as previously stated eating and drinking

various substances can arti1047297cially affect cortisol levels thus these

1047297ndings should be interpreted with caution (Goodyer et al 1996)

Given the limited evidence thus far and the possible methodolog-

ical shortcomings of the study by Banasik et al it is unclear at this

stage if yoga practice affects daytime cortisol

324 Waking and bedtime salivary cortisol

Findings of the effects of yoga classes on waking cortisol levels

are mixed Danucalov et al reported that hatha yoga in conjunction

with compassion meditation was associated with decreased sali-

vary waking cortisol depression anxiety and stress when prac-

ticed for eight weeks in familial caregivers as compared to a non-

treatment control group (Danucalov et al 2013) Banasik et al

also found that eight weeks of Iyengar yoga practice was associated

with lower morning cortisol and better emotional well-being

among breast cancer survivors Participants recorded the time of

collection on tracking forms with 95 of collections occurring

within 20 min of the assigned times and cortisol samples were

collected over two consecutive days at each time point in this study

(Banasik et al 2011) Chandwani et al found that in patients withbreast cancer a six-week yoga program involving a range of

physical yoga asanas was associated with a steeper cortisol slope

and decreased fatigue compared to individuals in a stretching or

waitlist control group at the end of radiotherapy A limitation of

this study is that the particular wake up time of individual partic-

ipants was not controlled for however samples were taken at the

same time intervals after waking for three consecutive days at each

time point (Chandwani et al 2014) and CAR has been shown to be

relativity stabile across consecutive days (Edwards et al 2001) In

another group of 56 patients with breast cancer Vadiraja et al

demonstrated that six weeks of yoga decreased waking and

bedtime salivary cortisol which corresponded to reduced depres-

sion anxiety and perceived stress as compared to brief supportive

therapy It should be noted that the brief supportive therapy groupreceived three-four 15 min individual counselling sessions during

six weeks whereas the yoga group received 18e24 yoga sessions

(Vadiraja et al 2009) Rocha et al found that six months of yoga

plus physical exercise was associated with decreased waking

cortisol depression anxiety and stress compared to exercise alone

among male Brazilian military personal However this study only

took a single waking cortisol measure at each collection time point

(Rocha et al 2012)

Contrarily Corey et al observed that after six month of

stretching or restorative yoga classes individuals in the stretching

conditions showed reduced waking and bedtime cortisol and had

lower self-perceived stress ratings than those in the restorative

yoga group Notably in the stretching condition poses were

changed approximately every 30s while in the restorative yoga




condition they were changed every 10e15min The authors spec-

ulated that these results might be due to increased physical activity

in the stretching condition This hypothesis is inconsistent with the

above-discussed 1047297ndings of Rocha et al who reported that yoga

plus exercise was more effective than exercise alone at lowering

cortisol levels (Rocha et al 2012) Alternatively post hoc analysis in

the study by Corey et al showed that increased perceived social

support in the stretching group was related to changes in cortisol

In the stretching intervention individuals partook in weekly dis-

cussion while in the restorative yoga group communication be-

tween participants was minimal (Corey et al 2014) These results

indicate that physical practices that incorporate a social aspect may

be more effective in modulating HPA activity Participants in this

study were asked to collect their morning cortisol sample before

11am so exact time of collection was not held constant between all

participants however 4 samplesday for three consecutive days

were collected from each participant at each time point the au-

thors found no signi1047297cant variance across the three test days and

the 1047297nal cortisol measure was averaged over the three days (Corey

et al 2014)

A pilot RCT by Hallgren et al involving 18-alcohol dependent

individuals showed that a 10-week yoga program was associated

with a non-signi1047297cant reduction in morning cortisol and alcoholconsumption at six months The authors speculated that the small

sample size might explain the absences of a signi1047297cant effect A

methodological limitation of this study is that individuals were not

tested upon completion of the yoga intervention but instead at six

months approximately three months after the completion of the

program Additionally no information was provided regarding the

time of day for cortisol collection or if multiple samples were

collected and thus this study appears to lack methodological rigour

(Hallgren et al 2014) In a small study involving 28 university

students experiencing mildmoderate depression Woolery et al

reported that 1047297ve weeks of Iyengar yoga decreased depression and

anxiety scores however there was only a trend for higher morning

cortisol In this study however only one salivary sample (waking

cortisol) was taken at each time point and the waking time of participants was not reported Thus these results should be inter-

preted with caution (Woolery et al 2004)

325 Serum cortisol

Only one reviewed study collected serum cortisol Sarubin et al

found that1047297veweeks of hatha yoga alongsidewitheitheran SSRI or

an atypical antipsychotic did not in1047298uence daytime serum cortisol

levels when compared to the SSRI or an atypical antipsychotic

alone in individuals with major depressive disorder Since both

medications were seen to decrease cortisol levels over time it is

possible that the additive effects of yoga were too small to be

detected Additionally the authors noted that the yoga intervention

used in this trial (5 60 min over 1047297ve weeks) was arguably too

short to result in endocrinological changes (Sarubin et al 2014)

326 Autonomic measures

There is strong evidence for the bene1047297cial effects of yoga on

stress-related autonomic measures such as blood pressure and

heart rate One small study by Tolbanos Roche et al involving 20

individuals with hypertension showed that a yoga program was

associated with reduced blood pressure stress anxiety and nega-

tive affect (Tolbanos Roche and Mas Hesse 2014) In 238 individuals

with hypertension Sujatha et al demonstrated that a 12 week

hatha yoga program was associated with a decrease in heart rate

blood pressure anxiety and perceivedstress compared to a waitlist

control group (Sujatha and J A 2014) In healthy women Kanojia

et al demonstrated that yoga decreased premenstrual associated

increases in blood pressure anger depression and anxiety and was

associated with a lower heart rate when compared to a no treat-

ment control group This effect was statistically signi1047297cant in the

second and third menstrual cycle after beginning practice (Kanojia

et al 2013) Innes et al showed that an eight-week Iyenger yoga

program decreased blood pressure anxiety perceived stress and

improved mood and sleep quality in women with restless-leg

syndrome when compared to individuals exposed to an educa-

tional 1047297lm program (Innes and Selfe 2012) In a trial involving

patients with osteoarthritis of the knee Ebnezar et alreported that

yoga in conjunction with conventional physiotherapy was associ-

ated with reduced blood pressure heart rate anxiety pain and

stiffness compared to physiotherapy exercises alone (Ebnezar et al

2012) These results suggest that yoga practices may have mood

and nervous system mediating effects beyond those associated

with targeted physical rehabilitation McDermott et al found that

eight weeks of either yoga or walking decreased blood pressure

anxiety depression and perceived stress with no difference be-

tween intervention groups on these measures in people with

elevated blood glucose (McDermott et al 2014) Finally Malathi

et al showed that in a sample of 75 healthy university students

that three months of yoga or relaxation was associated with

decreased changes in heart rate blood pressure galvanic skin

relaxation and anxiety during examination period as compared toa no treatment control group (Malathi et al 1998)

Only two studies measured the in1047298uence of yoga practice on

HRV Cheema et al found no effect of yoga practice on HRV in

healthy individuals but instead found that yoga was associated

with increased resting heart rate At baseline the yoga group had a

lower resting heart rate than the control group representing a

possible sampling bias (yoga group 62 plusmn 6 beatsmin control group

68 plusmn 10 beatsmin) The authors stipulated that the post interven-

tion increase in heart rate might have represented regression to the

mean in the yoga group Indeed heart rate was seen to be similar

between groups post intervention (yoga group 65 plusmn 9 beatsmin

control group 67 plusmn 9 beatsmin) (Cheema et al 2013) Telles et al

similarly failed to demonstrate an increase in HRV among 1047298ood

survivors in the single study investigating Patanjali Yogacompared to a wait list control group Telles et al speculated that

this lack of difference between groups might have been due to the

short one-week intervention period or low statistical power ( Telles

et al 2010) Thus in these two studies it appears that yoga practice

does not increase parasympathetic nervous system activity or

improve the balance between the sympathetic and para-

sympathetic systems

327 Immune changes

In a trial involving 186 breast cancer survivors Kiecolt-Glaser

et al demonstrated that a hatha yoga program reduced the pro-

duction of Interleukin-6 Tumor Necrosis Factor-alpha and Inter-

lukin-1beta cytokine from isolated peripheral blood mononuclear

cells stimulated with lipopolysaccharide (the major component of the outer membrane of Gram-negative bacteria which is often used

to induce an acute immune response (Kulp and Kuehn 2010)) as

well as decreasedfatigue and increased vitality but hadno effecton

depression scores compared to a waitlist control group when

measured at three months follow up from the 12 week program

Yoga participants did not report changes in perceived social sup-

port compared to the control group suggesting that social support

was not a mediating factor in their 1047297ndings (Kiecolt-Glaser et al

2014) Gopal et al showed that in university students 12 weeks

of yoga before examinations was associated with less exam related

increases in serum cortisol and decreases in the cytokine Inter-

feron gamma (IFN-g) Decreased serum IFN-g indicates a decline in

cellular immunity and thus the authors interpreted these 1047297ndings

to suggest that yoga may protect against stress related immune




suppression during situations of high stress (Gopal et al 2011)

Based on these 1047297ndings it appears that changes in cytokine levels

associated with yoga practice may contribute to changes in

behavioural outcomes

328 Yoga and brain measures

As illustrated in Table 1 only one RCT to date has collected both

measures of brain functioning in individuals practising yoga

(Streeter et al 2010b) Thestudy by Streeter et al was conducted in

the United States and included a cohort of mentally healthy in-

dividuals The authors used magnetic resonance spectroscopy

(MRS) prior to and following a 12-week Iyengar yoga or walking

program to determine Gamma-Aminobutyric Acid (GABA) levels in

the thalamic regions Notably this important neurotransmitter is

reduced across the spectrum of mood disorders This study

demonstrated that yoga was associated with decreased anxiety and

improved mood Further GABA levels positively correlated with

mood scores and negatively correlated with anxiety scores

(Streeter et al 2010b) The positive correlation between GABA

levels and mood scores suggests that GABA may at least in part

mediate the bene1047297ts of yoga on mood The link between the GABA

system and the in1047298ammatory response is still equivocal Current

models of allostatic stress in psychiatry state that exposure totrauma has negative physiological effects and may induce a

decrease in GABA levels which is an indicator of increased

in1047298ammation (McEwen 2003) Therefore it could be argued that

the reduction in GABA levels observed in the Streeter et al study

may be associated with stress and that yoga counteracts this pro-

cess by inhibiting the functioning of the HPA system (Streeter et al

2012)

We were unable to identify any further RCTs investigating the

effects of yoga practice on mood and functional connectivity We

did however identify two small pre-post intervention studies In

one such study from the United States and involving 4 yoga naive

individuals participants were seen to have a decreased resting

cerebral blood 1047298ow ratio in the right amygdala dorsal medial cor-

tex and sensorimotor area after 12 weeks of Iyanger yogacompared to baseline and assessed using single-photon emission

computed tomography Additionally the change in cerebral blood

1047298ow from baseline to after a mediation session was smaller in the

dorsal medial frontal lobe PFC and right sensorimotor cortex post

12 weeks of Iyanger yoga compared to at baseline ( Cohen et al

2009) In another small pre-post intervention study from India

and involving seven healthy elderly individuals six months of yoga

practice comprising of asanas and pranayama was reported to in-

crease hippocampal volume as assessed using magnetic resonance

imaging (Hariprasad et al 2013) Neither of the two above dis-

cussed pre-post intervention studies had a mood or well-being

related outcome measure

33 Differences in yoga forms and studied populations on arousal

The reviewed studies varied greatly in terms of the studied

populations forms of yoga practiced and biological outcomes In

terms of trials using a hatha yoga based intervention one study by

Sujatha et al showed that yoga was associated with changes in

blood pressure and heart rate (Sujatha and J A 2014) Smith et al

found no effect of hatha yoga practice on blood pressure (Smith

et al 2007) and Cheema et al found no effect of hatha yoga

practice on HRV (Cheema et al 2013) The studies by Smith et al

and Cheema et al only required participant to engage in 150 min

and 60 min of yoga practice a week respectively (Smith et al 2007

Cheema et al 2013) This was compared to compared to 600 min

followed by at least 150 min a week in the study by Sujatha et al

(Sujatha and J A 2014) One hatha yoga based study by Danucalov

et al showed a change in salivary cortisol (Danucalov et al 2013)

while a second hatha yoga study by Sarubin et al reported no

change in serum cortisol (Sarubin et al 2014) The Sarubin et al

study only required participants to engage in 60 min of practice a

week for 1047297ve weeks (Sarubin et al 2014) compared to 225 min a

week for eight weeks in the study by Danucalov et al (Danucalov

et al 2013) Kiecolt-Glaser et al (Kiecolt-Glaser et al 2014)

found that in 186 breast cancer survivors that women who prac-

ticed hatha yoga for a longer time period each day showed greater

reductions in fatigue and increases in vitality at post treatment and

three months follow up as well as a greater decease in lipopoly-

saccharide stimulated Interleukin-6 and Interlukin-1beta produc-

tion from isolated peripheral blood mononuclear cell at three

months follow up from the 12 week program As little as a 10 min

increase in daily yoga practice was associated with a 1047297ve-

percentage decrease in the IL-6 and an eight-percentage decrease

IL-1b geometric mean (Kiecolt-Glaser et al 2014) Thus collectively

these studies suggest that the dose of yoga practice is likely an

important mediating factor in terms of modulation of the SNS or

levels of the stress hormone cortisol

A further possible mediating factor on the effect of yoga on

biological outcomes is the population studied In the three hatha

yoga studies that found no biological changes the included patientswere those with major depressive disorder or healthy adults (Smith

et al 2007 Cheema et al 2013 Sarubin et al 2014) In the three

hatha yoga studies that reported a biological effect the participants

were breast cancer survivors individuals with hypertension and

healthy familial caregivers (Sujatha and J A 2014 Kiecolt-Glaser

et al 2014 Danucalov et al 2013) It is therefore possible that

yoga practice mediates SNS activation more effectively in some

populations than in others For example prenatal yoga was seen to

decrease salivary cortisol in both of the reviewed studies involving

pregnant women (Field et al 2013 Newham et al 2014) even

when only practiced for 20 min a week for 12 weeks ( Field et al

2013) Cortisol endogenously elevates during pregnancy and thus

this population mayshow a greater likelihood of decreasing cortisol

(Mastorakos and Ilias 2003) It is also possible that the effects of theyoga practice are great enough to elicit a decrease in cortisol in

spite of elevated levels

Biological outcomes were available for only three studies

investigating the effects of Iyengar yoga two of which involved

healthy adults and found no effect on salivary cortisol (Woolery

et al 2004 Bowden et al 2012) One study involved women

with restless leg syndrome and found that Iyengar yoga decreased

blood pressure but not heart rate (Innes and Selfe 2012) Restor-

ative yoga was similarly seen not to in1047298uence salivary cortisol in

one study (Corey et al 2014) Thus the preliminary data suggests

that hatha and prenatal yoga may be more effective than restor-

ative or Iyengar yoga in mediating SNS activity and the HPA axis It

is possible that Iyengar yoga does not effectively mediate SNS ac-

tivity in healthy individuals However there are too few studiesavailable and 1047297ndings are too inconsistent to draw conclusions in

this regard

Ten studies did not specify the type of yoga interventions used

however 1047297ve of these were seen to in1047298uence heart rate andor

blood pressure (McDermott et al 2014 Kanojia et al 2013

Ebnezar et al 2012 Malathi et al 1998 Tolbanos Roche and Mas

Hesse 2014) two were seen to in1047298uence salivary cortisol

(Vadiraja et al 2009 Chandwani et al 2014) and one to in1047298uence

serum cortisol and IFN-g but not heart rate or blood pressure

(Gopal et al 2011)

Overall the studies reviewed provide preliminary evidence that

various forms of yoga practice including hatha and prenatal yoga

are associated with biological changes including cortisol levels SNS

activation decreased stress and negative affect Programs involving




more hours of yoga practice per week seem to be more effective

than those with fewer hours Based on current 1047297ndings yoga does

not appear to mediate SNS or HPA activity as effectively in healthy

individuals However it is still unknown what aspects of the yoga

intervention are effective for example previous research shows

bene1047297cial effects of exercise (Craft and Perna 2004) meditation

(Goyal et al 2014) and mindfulness (Piet and Hougaard 2011) all

of which yoga practice encompasses

4 Discussion

Yoga is commonly used as a form of stress management

(Penman et al 2012) with practicing individuals reporting a

preference for self-management over clinical intervention no side

effects and a perceived ef 1047297cacy of yoga greater than that of con-

ventional medication (Pilkington et al 2005 Issakidis and

Andrews 2002 Jorm et al 2000a Jorm et al 2000b) The posi-

tive public perception of yoga is demonstrated by its growing

popularity In the United States approximately 95 of the popu-

lation were practising yoga in 2012 compared to 61 in 2007

(Clarke et al 2015) In Australia approximately 35 of the popu-

lation was practicing yoga in 2010 compared to 29 in 2006

(Australian Sports Commission and tSRGS 2010) In England upto 128 of the population were practicing in 200608 compared to

046 in 199799 (Ding and Stamatakis 2014) Accordingly medical

providers such as general practitioners are more commonly rec-

ommending yoga as a treatment method to their patients In the

United States approximately 144 million people where prescribed

yoga by their doctor in 2011 (Nerurkar et al 2011) A recent

Australian survey reports that 121 of general practitioners in New

South Wales recommended yoga therapies to their patients A

many as 766 of practitioners referred their patients to a yoga

therapist at least a few times during the year while 125 of

practitioners referred patients at least once per week (Wardle et al

2014)

Some individuals may 1047297nd yoga practice more appealing than

pharmacological therapies as it allows participants to be activelyengaged in therapy and as yoga can be utilised at periods of high

anxietydepression which empowers the individual in self-

management Additionally yoga practice may not be perceived to

lsquoarti1047297ciallyrsquo affect biochemical processes in the manner that phar-

maceutical interventions may be

However and despite the growing popularity of yoga practice

its neurobiological effects arestill largely notunderstood While the

literature-reviewed in the present systematic review suggests that

yoga practice appears to improve positive affect and decrease

depressive and anxious symptomology in diverse populations

many of the reviewed studies are characterised by small sample

size no follow up and the yoga interventions are not well

described making study replication and interpretation dif 1047297cult

Additionally in a number of studies the method of salivary cortisolcollection is characterised by a lack of rigor Indeed Table 1 shows

that many of the reviewed studies are published in lower impact

journals which at times can be re1047298ected by the methodological

quality of the studies Yoga research is a developing 1047297eld with a

dif 1047297cult to de1047297ne taxonomy (Ospina et al 2007) and arguably with

a reputation for poor methodological rigour This perception within

the scienti1047297c community may limit the availability of research

funding and thus further impair the production of high quality

research trials

Despite methodological limitations the large majority of the

studies provide some evidence that yoga is associated with bio-

logical changes in blood pressure heart rate cortisol or cytokine

levels It is therefore plausible that yoga may affect mood via SNS

and HPA axis regulation Further studies are required in order to

con1047297rm the preliminary1047297ndings that yoga appears to in1047298uence the

stress response and to explore the effects of yoga on the neural

correlates in the context of mood changes

Disclosurecon1047298ict of interest

The authors declare no con1047298ict of interest

Contributors

Michaela Celeste Pascoe designed the protocol conducted the

systematic review and wrote the manuscript Isabelle E Bauer

contributed to design of the protocol the systematic review and

the writing of the manuscript All authors have approved the 1047297nal

article

Role of the funding source

The was no funding source for this research

Acknowledgements

The authors have no acknowledgments to declare

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83Schatzberg AF 2007 Safety and tolerability of antidepressants weighing the

impact on treatment decisions J Clin Psychiatry 68 (Suppl 8) 26e34Schulberg HC Katon WJ S MK 1998 Management of mood and anxiety dis-

orders in primary care In Rush AJ (Ed) Mood and Anxiety Disorders CurrentScience Inc Philadelphia PA

Sharma VK et al 2006 Effect of Sahaj Yoga on neuro-cognitive functions in pa-tients suffering from major depression Indian J Physiol Pharmacol 50 (4)375e383

Sheline YI Gado MH Kraemer HC 2003 Untreated depression and hippo-campal volume loss Am J Psychiatry 160 (8) 1516e1518

Shyn SI Hamilton SP 2010 The genetics of major depression moving beyondthe monoamine hypothesis Psychiatr Clin North Am 33 (1) 125e140

Siegle GJ et al 2002 Cant shake that feeling assessment of sustained event-related fMRI amygdala activity in response to emotional information indepressed individuals Biol Psychiatry 51 (9) 693e707

da Silva TL Ravindran LN Ravindran AV 2009 Yoga in the treatment of moodand anxiety disorders a review Asian J Psychiatr 2 (1) 6e16

Silverman MN Sternberg EM 2012 Glucocorticoid regulation of in1047298ammationand its functional correlates from HPA axis to glucocorticoid receptordysfunction Ann N Y Acad Sci 1261 55e63

Smith C et al 2007 A randomised comparative trial of yoga and relaxation toreduce stress and anxiety Complement Ther Med 15 (2) 77e83

Streeter CC et al 2010 Effects of yoga versus walking on mood anxiety and brainGABA levels a randomized controlled MRS study J Altern Complement Med16 (11) 1145e1152

Streeter CC et al 2010 Effects of yoga versus walking on mood anxiety and brainGABA levels a randomized controlled MRS study J Altern ComplementaryMed 16 (11) 1145e1152

Streeter CC et al 2012 Effects of yoga on the autonomic nervous system gamma-aminobutyric-acid and allostasis in epilepsy depression and post-traumaticstress disorder Med Hypotheses 78 (5) 571e579

Sujatha T J A 2014 Efectivenes of a 12-Wek yoga program on physiopsychologicalparameters in patients with hypertension Int J Pharm Clin Res 6 (4)329e335

Telles S et al 2010 Post traumatic stress symptoms and heart rate variability inBihar 1047298ood survivors following yoga a randomized controlled study BMCPsychiatry 10 18

Tindle HA et al 2005 Trends in use of complementary and alternative medicineby us adults 1997-2002 Altern Ther Health Med 11 (1) 42e49

Tolbanos Roche L Mas Hesse B 2014 Application of an integrative yoga therapyprogramme in cases of essential arterial hypertension in public healthcareComplement Ther Clin Pract 20 (4) 285e290 httpdxdoiorg101016

jctcp201410004Travis F Pearson C 200 0 Pure consciousness distinct phenomenological and

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Uebelacker LA et al 2010 Hatha yoga for depression critical review of the evi-dence for ef 1047297cacy plausible mechanisms of action and directions for futureresearch J Psychiatr Pract 16 (1) 22e33

Vadiraja HS et al 2009 Effects of a yoga program on cortisol rhythm and moodstates in early breast cancer patients undergoing adjuvant radiotherapy arandomized controlled trial Integr Cancer Ther 8 (1) 37e46

Wardle J Adams J Sibbritt D 2014 Referral to yoga therapists in rural primaryhealth care a survey of general practitioners in rural and regional New SouthWales Australia Int J Yoga 7 (1) 9e16

Weibel L 2003 Methodological guidelines for the use of salivary cortisol as bio-logical marker of stress Presse Med 32 (18) 845e851

West J et al 2004 Effects of Hatha yoga and African dance on perceived stressaffect and salivary cortisol Ann Behav Med 28 (2) 114e118

Whiteford HA et al 2013 Global burden of disease attributable to mental andsubstance use disorders 1047297ndings from the global Burden of Disease Study 2010Lancet 382 (9904) 1575e1586

Wittchen HU et al 2011 The size and burden of mental disorders and otherdisorders of the brain in Europe 2010 Eur Neuropsychopharmacol 21 (9)655e679

Woolery A et al 2004 A yoga intervention for young adults with elevatedsymptoms of depression Altern Ther Health Med 10 (2) 60e63

Yang Y Raine A 2009 Prefrontal structural and functional brain imaging 1047297ndingsin antisocial violent and psychopathic individuals a meta-analysis PsychiatryRes 174 (2) 81e88

Yeung A et al 2014 Randomised controlled trial of a 12 week yoga intervention

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del Zoppo G et al 2000 In1047298ammation and stroke putative role for cytokinesadhesion molecules and iNOS in brain response to ischemia Brain Pathol10 (1)95e112




posttraumatic stress disorder Additionally recent models of neu-

roprogression suggest that the hippocampal atrophy observed in

unipolar depression is cumulative as the degree of atrophy appears

to be related to the number of untreated episodes and illness

duration (Sheline et al 2003 Berk et al 2011 Fries et al 2012)

One could therefore argue that the relationship between structural

brain abnormalities and affective disorders is bidirectional

The aetiology of depressive and anxious disorders are complex

and polygenetic and additional to structural abnormalities in-

dividuals show abnormalities in the function and expression of

monoamine neurotransmitters such as serotonin and dopamine

(Krishnan and Nestler 2008 Morilak and Frazer 2004) increased

oxidative stress (Michel et al 2012 Bouayed et al 2009) decreased

expression of the neurotropic protein brain-derived neurotrophic

factor (BDNF) (Autry and Monteggia 2012) and changes in the

expression of cytokines (Dantzer 2012) Cytokines are small cell

signalling protein molecules essential in the innate immune

response and in1047298ammation Cytokines can be either pro or anti-

in1047298ammatory (del Zoppo et al 2000) and among other functions

stimulate the autonomic nervous system (ANS) and the hypotha-

lamic pituitary adrenal (HPA) axis (Silverman and Sternberg 2012)

The ANS has two main divisions the parasympathetic nervous

system (PNS) and the sympathetic nervous system (SNS) TheSNS isinvolved in the mobilisation of the body in situations of stress to

either lsquo1047297ght or 1047298ightrsquo the stressor The PNS is responsible for

returning the body to a homoeostatic state after the activation of

the SNS (Buijs 2013) In many cases the PNS and SNS have com-

plementary and opposing actions in that one system is responsible

for activating a physiological response and the other is responsible

for inhibiting it (Buijs 2013) Activation of the SNS is associated

with a number of physiological changes including increased heart

rate blood pressure HPA axis activation and subsequent down-

stream release of the glucocorticoid hormone cortisol from the

adrenal cortex (Raison et al 2006) Glucocorticoid levels and the

further synthesis of pro-in1047298ammatory cytokines are normally

regulated by a HPA axis negative feedback mechanism (Silverman

and Sternberg 2012)The reciprocal relationship among stress HPA axis regulation

and depression and anxiety is well known (Dantzer 2012 Dantzer

et al 2008 Maes 2008a) Clinical depression and anxiety are

associated with an increased in1047298ammatory state These conditions

are characterized by dysfunctional glucocorticoid feedback inhibi-

tion (Silverman and Sternberg 2012) hypersecretion of CRH HPA

axis dysfunction (Boyer 2000 Roy-Byrne et al 1986) increased

circulatory cortisol (a widely used biomarker of HPA axis dysfunc-

tion) (Olson et al 2012) and production of pro-in1047298ammatory cy-

tokines (Silverman and Sternberg 2012 Raison et al 2006

Sapolsky et al 2000 King and Hegadoren 2002) Anxiety related

sustained central arousal has been proposed to deplete neuro-

transmission in the forebrain and thus precipitate the onset of

depression (Neale and Kendler 1995 Eison 1990 Johnson et al1990 Nutt et al 1998 Schulberg et al 1998)

On the other hand chronic stress and in1047298ammation can

contribute to the onset of depressive and anxious symptoms

(Dantzer 2012 Masi and Brovedani 2011 Pascoe et al 2011)

Treatment with the in1047298ammatory cytokine Interferon-a (INF-a)

(Capuron and Miller 2004) has been associated with the presen-

tation of depressive and anxious symptoms in cancer survivorships

(Capuron et al 2002) These depressive symptoms resolve with

INF-a therapy termination (Capuron and Dantzer 2003) and anti-

depressant medication (Musselman et al 2001)

Finally the bene1047297cial effects of pharmaceutical antidepressant

medications appear to relate to their in1047298uence on in1047298ammatory

activity Tricyclic antidepressant medications reduce pro-

in1047298

ammatory Interleukin-1 (IL-1) and Interleukin-2 (IL-2) and

increase anti-in1047298ammatory Interleukin-10 in animal models

(Kubera et al 2000) suggesting that these pharmaceutical anti-

depressant medications likely reduce depressive symptoms at

least in part by mediating mood modulating in1047298ammatory

markers (Kubera et al 2000) Additionally high basal in1047298amma-

tion is associated with a treatment resistance to pharmaceutical

anti-depressant interventions in clinical populations An

increased in1047298ammatory state as characterised by heightened

plasma concentrations of in1047298ammatory cytokines and acute phase

proteins prior to antidepressant treatment is associated with a

non-response (Maes 2008b Raison et al 2013)

Not only are current pharmacological treatment methods such

as selective serotonin reuptake inhibitors (SSRI) not bene1047297cial for

all individuals (Howland 2006 Kirsch et al 2008) these medica-

tions are associated with deleterious side effects such as metabolic

disorders and diabetes (McIntyre et al 2010) that reduce quality of

life and negatively in1047298uence individual adherence to the medica-

tion (Schatzberg 2007) Thus there is need for safer and more

effective treatment methods for mood disorders

12 Yoga is an effective treatment for depressive and anxious

symptomatology

The termyogais Sanskrit for lsquounionrsquo or lsquoto yokersquo and describes a

lifestyle aiming to achieve union of mind body and spirit While the

origins of yoga are unclear the Indian sage Patanjali described eight

limbs of yoga (G F 1998) which have been performed in Eastern

cultures for thousands of years In recent years yoga has become

increasingly popular in Western cultures (Ding and Stamatakis

2014 Tindle et al 2005) There are many forms of yoga each

with unique approaches and theoretical underpinnings making a

de1047297nitive taxonomy dif 1047297cult (Ospina et al 2007) Previous authors

have noted that this lack of a de1047297nitive de1047297nition and subsequent

differences in the forms studied has hampered neuroscienti1047297c

research in this 1047297eld (Lutz et al 2007) All forms of yoga however

share common elements including use of controlled breathing

(pranayama) physical postures (asanas) and meditative techniques(dhyana) to achieve well-being and mind body union and balance

(Farmer 2012 P1047298ueger 2011 Travis and Pearson 2000) Several

studies and systematic reviews demonstrate the mood enhancing

effects of yoga as treatments for clinical depression ( Uebelacker

et al 2010 Pilkington et al 2005 DSilva et al 2012

Balasubramaniam et al 2012) and anxiety (Chattha et al 2008

Granath et al 2006 Banerjee et al 2007 Harinath et al 2004

Kjellgren et al 2007 West et al 2004 Woolery et al 2004

Smith et al 2007 Li and Goldsmith 2012) Yoga practice is asso-

ciated with a reduced number of major depressive episodes and

lower risk for dysthymia which is a milder but longer-term form of

depression (Banerjee et al 2007 Kjellgren et al 2007 Woolery

et al 2004 John et al 2007 Sharma et al 2006 Butler et al

2008) Meta-analyses and systemic reviews indicate that yogaand meditative therapies are equally effective as conventional an-

tidepressants in the treatment of depressive and anxious disorders

(da Silva et al 2009 Cramer et al 2013 Chen et al 2012) The

limited data thus far suggests that these practices are associated

with changes in the stress response (Kinser et al 2012 McCall

2013) The neurobiological mechanisms however via which yoga

exerts its mood enhancing effects are still not clearly understood

2 Methods

21 Systematic search strategy

In the present study we aimed to systematically review rand-

omised control trials (RCTs) investigating the effects of yoga on
























tions were excluded

3 Results


































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065










































































































































































tions were excluded

3 Results


































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065




















































































































































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065


















































































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065
















































































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065














































































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065












































































































































































































levels



























































(Rocha et al 2012)





























et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065









































































































































































et al 2014)


















325 Serum cortisol

































































sympathetic systems

327 Immune changes

















































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065

















































































































































































2012)


















































































this regard








(Gopal et al 2011)
















4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065






























































































































































4 Discussion























2014)























research trials











Contributors





article



Acknowledgements


References
























1065








































































































































































































































































































































































Documents

documento cientifico de la Yoga.pdf