Generalized anxiety disorder prevalence and comorbidity with depression in coronary heart disease: a...

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http://hpq.sagepub.com/ Journal of Health Psychology http://hpq.sagepub.com/content/18/12/1601 The online version of this article can be found at: DOI: 10.1177/1359105312467390 2013 18: 1601 originally published online 8 January 2013 J Health Psychol Phillip J Tully and Suzanne M Cosh coronary heart disease: A meta-analysis Generalized anxiety disorder prevalence and comorbidity with depression in Published by: http://www.sagepublications.com can be found at: Journal of Health Psychology Additional services and information for http://hpq.sagepub.com/cgi/alerts Email Alerts: http://hpq.sagepub.com/subscriptions Subscriptions: http://www.sagepub.com/journalsReprints.nav Reprints: http://www.sagepub.com/journalsPermissions.nav Permissions: http://hpq.sagepub.com/content/18/12/1601.refs.html Citations: What is This? - Jan 8, 2013 OnlineFirst Version of Record - Nov 20, 2013 Version of Record >> at UNIVERSITY OF ADELAIDE LIBRARIES on November 21, 2013 hpq.sagepub.com Downloaded from at UNIVERSITY OF ADELAIDE LIBRARIES on November 21, 2013 hpq.sagepub.com Downloaded from

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http://hpq.sagepub.com/content/18/12/1601The online version of this article can be found at:

 DOI: 10.1177/1359105312467390

2013 18: 1601 originally published online 8 January 2013J Health PsycholPhillip J Tully and Suzanne M Cosh

coronary heart disease: A meta-analysisGeneralized anxiety disorder prevalence and comorbidity with depression in

  

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Journal of Health Psychology18(12) 1601 –1616© The Author(s) 2012Reprints and permissions: sagepub.co.uk/journalsPermissions.navDOI: 10.1177/1359105312467390hpq.sagepub.com

Introduction

Major depressive disorder (MDD) is the most commonly researched internalizing/emotional disorder in coronary heart disease (CHD) patients. Previous meta-analyses indicate that MDD and depression symptoms confer greater CHD morbidity risk (Barth et al., 2004; Nicholson et al., 2006), culminating in the American Heart Association advocating routine depression screening among these patients (Lichtman et al., 2008). However, the fact that depression screen-ing and intervention have only translated to a modest impact on cardiovascular outcomes (Baumeister et al., 2011; Pizzi et al., 2011)

suggests that what is understood about the MDD–CHD link is in the nascent stages and incomplete. Recent findings also indicate that

Generalized anxiety disorder prevalence and comorbidity with depression in coronary heart disease: A meta-analysis

Phillip J Tully1,2,3 and Suzanne M Cosh1

AbstractGeneralized anxiety disorder prevalence and comorbidity with depression in coronary heart disease patients remain unquantified. Systematic searching of Medline, Embase, SCOPUS and PsycINFO databases revealed 1025 unique citations. Aggregate generalized anxiety disorder prevalence (12 studies, N = 3485) was 10.94 per cent (95% confidence interval: 7.8–13.99) and 13.52 per cent (95% confidence interval: 8.39–18.66) employing Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria (random effects). Lifetime generalized anxiety disorder prevalence was 25.80 per cent (95% confidence interval: 20.84–30.77). In seven studies, modest correlation was evident between generalized anxiety disorder and depression, Fisher’s Z = .30 (95% confidence interval: .19–.42), suggesting that each psychiatric disorder is best conceptualized as contributing unique variance to coronary heart disease prognosis.

Keywordscomorbidity, coronary heart disease, depression, generalized anxiety disorder, meta-analysis

1The University of Adelaide, Australia2 School of Psychology, The University of Adelaide, Australia

3Cardiac Surgery Research and Perfusion, Department of Medicine, Flinders Medical Centre, Australia

Corresponding author:Phillip J Tully, Cardiac Surgery Research and Perfusion, Cardiac and Thoracic Surgical Unit, Flinders Medical Centre, Bedford Park, SA 5042, Australia. Email: [email protected]

467390 HPQ181210.1177/1359105312467390Journal of Health PsychologyTully and Cosh2012

Article

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1602 Journal of Health Psychology 18(12)

other emotional constructs such as anxiety and negative affect, in particular, increase CHD risk, raising the possibility that MDD is not a discrete psychiatric risk factor for CHD (Frasure-Smith and Lesperance, 2008; Martens et al., 2010; Phillips et al., 2009; Scherrer et al., 2010; Tully et al., 2011). In fact, the extent to which the recent CHD prognostic findings reflect unique depression variance, independent from anxiety and negative affect, remains largely unchallenged. Quantifying the degree of comor-bidity between MDD and anxiety disorders in CHD can help inform whether these disorders contribute independent variance to cardiovascu-lar prognosis or, alternatively, whether the co-occurrence of disorders largely reflects common variance (e.g. negative affect, shared diagnostic symptoms and artificial diagnostic splitting). Although the extent of overlap between psycho-social constructs in CHD has long been high-lighted as crucial to define (Kubzansky et al., 2006; Kubzansky and Kawachi, 2000; Smith, 2010); Suls and Bunde, 2005; Tully et al., 2008), we are not aware of a previous study to pool such data together and thereby quantify the associa-tion between depression and anxiety in CHD patients.

Among all psychiatric disorders, generalized anxiety disorder (GAD) is the most commonly comorbid disorder with MDD, both concur-rently and across the lifespan, among individu-als primarily free from CHD (Krueger, 1999; Sherbourne et al., 1996; Watson, 2009). In fact, in primary care settings over half of unipolar MDD, cases are comorbid with GAD (Sherbourne et al., 1996), so much so that scholars have long debated whether these even form separate diag-nostic and clinical disorders (Mennin et al., 2008). Explanations for high comorbidity between GAD and MDD include shared diag-nostic criteria (i.e. fatigability, restlessness/psychomotor agitation, concentration and sleep difficulties) (American Psychiatric Association, 2000), common genetic factors and common diathesis (Mineka et al., 1998) and related cog-nitive processes such as rumination and worry (Brosschot et al., 2006; Soo et al., 2009). For

these reasons, GAD would serve as a suitable diagnostic exemplar to determine the extent to which depression shares variance with anxiety among CHD patients.

The dilemmas imposed by the overlap between depression and GAD are exemplified further in recent aetiological and prognostic studies. Recent research generally supports that MDD is associated with CHD, though largely contrasting results have been reported for GAD. For example, a recent epidemiological survey of 43,093 US civilians showed that the largest psy-chiatric association with physician diagnosed cardiovascular disease was attributable to GAD, as opposed to any other affect or mood disorder (adjusted odds ratio (OR): 1.83; 95% confidence interval (CI): 1.39–2.39) (Goodwin et al., 2009). Some studies have suggested that GAD is asso-ciated with cardiovascular outcome independent of MDD (Frasure-Smith and Lesperance, 2008; Martens et al., 2010; Phillips et al., 2009; Tully et al., 2011) and another dataset reported reduced cardiovascular risk attributable to GAD (Parker et al., 2011), raising the possibility that these psychiatric disorders are highly collinear in CHD. Given that the degree of interrelation between GAD and MDD in CHD patients and the overall prevalence of GAD are not known, a critical gap is evident with respect to interpreta-tion of the extant literature, particularly aetio-logical and prognostic studies.

Only by identifying the prevalence of GAD and the comorbidity rates between GAD and MDD will the extent of potential confounding variance in the MDD–CHD association be known. If comorbidity between GAD and MDD is small, then both GAD and MDD might best be conceptualized as discrete psychiatric risk factors in CHD. This, in turn, could feasibly redirect psychosocial research and interven-tions towards treatments tailored towards the phenotypic processes and biobehavioural mechanisms that confer CHD risk, beyond sim-ply depression. Conversely, if high comorbidity rates were evident, research and intervention efforts may facilitate a shift away from disor-der-specific treatments towards transdiagnostic

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Tully and Cosh 1603

approaches targeting common and modifiable vulnerability risk factors for depression and anx-iety in CHD (Barlow et al., 2011; Dozois et al., 2009). Therefore, the purpose of this systematic review was to quantify the prevalence of GAD in CHD and comorbidity with MDD with two study aims:

1. What is the prevalence of GAD in popu-lations with verified CHD?

2. What are the current comorbidity rates between depression disorders and GAD in populations with verified CHD?

Methods

Literature search

Using standardized criteria (Stroup et al., 2000), one systematic search of the Medline, Embase, SCOPUS and PsycINFO electronic databases was performed for English language studies or unpublished doctoral dissertations, reporting the prevalence of GAD in CHD or comorbidity rates with depression published between January 1975 and May 2011. Free text searches without language restrictions included the term GAD in combination with CHD, cardiovascular disease, heart disease, ischaemic heart disease, myocar-dial infarction (MI), cardiac death, coronary artery bypass graft (CABG), percutaneous coro-nary intervention, angioplasty and heart failure. These cardiac search terms were then combined with ‘anxiety’ and several common structured diagnostic interview tools: Anxiety Disorder Interview Schedule (ADIS), Composite International Diagnostic Interview (CIDI), Diagnostic Interview Schedule (DIS), MINI International Neuropsychiatric Interview (MINI) and Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders, Third Edition, Revised (DSM-III-R) (SCID).

Selection criteria

Eligibility criteria were established before the literature search. Editorial, letter, case report,

conference abstract or qualitative reviews were excluded. Studies with post-stroke, cerebrovas-cular accident populations, heart transplant and mitral valve prolapse populations were also excluded, unless CHD patients were reported separately. Only studies with more than 50 patients were included to provide reliable prev-alence and comorbidity estimates and sufficient power for studies. Studies were eligible for inclusion if the sample showed physician veri-fied or documented CHD (e.g. positive stress test, coronary atherosclerosis, MI and coronary revascularization procedure) or end-stage heart failure. Studies employing only self-report CHD diagnosis/symptoms were ineligible.

Diagnosis of GAD and MDD (current and life-time) was derived from either structured inter-view or self-report with the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 1987, 2000, 2010) and International Classification of Diseases-10 (ICD-10; World Health Organization, 2007) criteria, or documented with relevant codes corroborated by a physician in medical records. Non-current International Classification of Disease codes for ‘anxiety states’ and ‘anxiety neurosis’ were not searched for and were excluded.

Data extraction

The two authors independently reviewed arti-cles for eligibility. In the case of title/abstract disagreements, the study was subjected to full-text review. Additional studies were identified by inspection of the reference section of arti-cles selected for full-text review. Disagreements were resolved by discussion. The quality of studies was not rated because there are no agreed upon measures of study quality, and the use of subjective rating scales may lead to bias (Petitti, 1994). Standardized data were extracted for each study including authors and citation, sample size, CHD sample characteristics, coun-try, age (mean (M), standard deviation (SD)) and percentage female sex, GAD criteria, current and lifetime GAD prevalence, GAD and MDD

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1604 Journal of Health Psychology 18(12)

comorbidity rates. Like other meta-analyses (Hackett et al., 2005), articles were judged to be from the same cohort if there was evidence of overlapping study dates, recruitment sites and similar study sample characteristics and grant funding numbers. In the case of multiple reports for the same sample, the study with the most comprehensive data and largest sample was retained.

Search results

Figure 1 displays the flow chart for exclusion and selection of studies. Table 1 describes the characteristics of the included studies reporting GAD prevalence and CHD outcomes in CHD. From 1025 unique citations, 934 were excluded by title/abstract (Kappa agreement = .91). Among 91 subjected to full-text review, in

Full Text Review(n = 91)

+ 15 identified by manualsearching

Title/Abstract Exclusion(n = 934)

Non-CHD (n = 728)GAD not reported (n = 120)Review (n = 31)Paediatric (n = 7)Case report/letter (19)Stroke (n = 15)Non-English (n = 13)Animal (n = 1)

Primary Literature Search

(n = 1,025)

Full Text Exclusion(n = 94)

Not CHD / mixed (n = 27)None / insufficient GAD

prevalence (n = 41)Self-report CHD (n = 5)

Case-report/review (n = 7)< 50 patients (n = 3)

Duplicate sample (n = 11)

Met Inclusion Criteria Aim 1(n = 12)

Met Inclusion Criteria Aim 2

Reported proportion of GADpatients with MDD

(n = 3)

Met Inclusion Criteria Aim 2

Reported proportion ofMDD patients with GAD

(n = 4)

Figure 1. Flow chart of selected studies.CHD: coronary heart disease; GAD: generalized anxiety disorder; MDD: major depressive disorder.

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Tully and Cosh 1605Ta

ble

1. O

verv

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ount

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AU

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1606 Journal of Health Psychology 18(12)

Stud

yC

ount

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me;

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IS: a

nxie

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ule;

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ustr

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; CA

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: sta

ndar

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viat

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sta

ndar

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ror;

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-III:

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gnos

tic a

nd S

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tical

Man

ual o

f Men

tal D

isord

ers,

Third

Edi

tion;

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-III-R

: Dia

gnos

tic a

nd S

tatis

tical

M

anua

l of M

enta

l Diso

rder

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ird E

ditio

n, R

evis

ed; D

SM-IV

: Dia

gnos

tic a

nd S

tatis

tical

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ual o

f Men

tal D

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Four

th E

ditio

n; M

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or d

epre

ssiv

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sord

er.

a Num

ber

of G

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cas

es is

the

den

omin

ator

; num

ber

of d

epre

ssio

n ca

ses

is t

he n

umer

ator

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umbe

r of

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ress

ion

case

s is

the

den

omin

ator

; num

ber

of G

AD

cas

es is

the

num

erat

or.

c Mar

tens

et

al. (

2010

) re

port

ed u

sing

DIS

to

dete

rmin

e G

AD

and

MD

D w

ith D

SM-IV

cri

teri

a, h

owev

er, r

efer

red

to t

he D

SM-II

I ver

sion

. The

aut

hors

rep

orte

d 12

-mon

th

GA

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ates

.d F

rasu

re-S

mith

and

Les

pera

nce

(200

8) a

lso

repo

rted

com

orbi

dity

for

17 o

ut o

f 43

GA

D p

atie

nts

with

pas

t hi

stor

y of

dep

ress

ion

indi

catin

g a

com

orbi

dity

rat

e of

39.

53 (

95%

C

I 25.

99-5

4.44

) e P

arke

r et

al.

(201

1) r

epor

ted

lifet

ime

GA

D c

omor

bid

with

dep

ress

ion/

dyst

hym

ia. A

CID

I + r

esea

rch

assi

stan

t pr

eval

ence

was

als

o re

port

ed fo

r cu

rren

t (1

5.5%

) an

d lif

etim

e G

AD

(28

.6%

).f T

ully

et

al. (

2008

) de

pres

sion

com

orbi

dity

cou

ld n

ot b

e ca

lcul

ated

bec

ause

onl

y hi

erar

chic

al e

xclu

sion

rul

es w

ere

repo

rted

.g F

edor

off e

t al

.’s (

1991

) di

agno

stic

cri

teri

a ar

e co

nsis

tent

with

DSM

-III G

AD

and

MD

D c

rite

ria.

h Ban

kier

et

al. (

2008

) re

port

ed 1

1 ou

t of

30

GA

D c

ases

in m

ixed

MD

D/a

nxie

ty g

roup

and

4/3

0 G

AD

cas

es in

anx

iety

-onl

y gr

oup.

The

fina

l rep

orte

d sa

mpl

e w

as r

estr

icte

d to

eith

er d

epre

ssio

n on

ly (

n =

30)

, no

psyc

hiat

ric

diso

rder

(n

= 3

0), m

ixed

dep

ress

ion–

anxi

ety

(n =

30)

and

anx

iety

onl

y (n

= 3

0) fr

om w

hich

the

2 ×

2 c

ontin

genc

y ta

ble

for

com

orbi

d G

AD

am

ong

MD

D w

as c

alcu

late

d.i H

awor

th e

t al

. (20

05)

repo

rted

dep

ress

ion

diso

rder

s (2

2 ou

t of

98,

tot

al 2

5%)

as m

ajor

dep

ress

ion

(14.

8%),

dyst

hym

ia (

2.3)

, min

or d

epre

ssio

n (2

.3),

brie

f dep

ress

ion

diso

r-de

r (3

.4)

and

adju

stm

ent

diso

rder

with

dep

ress

ion

(1.1

).

Tabl

e 1.

(C

ontin

ued)

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Tully and Cosh 1607

addition to 15 identified by manual searching, a further 94 were excluded. A total of 12 studies were retained that reported GAD prevalence and seven of these also reported comorbidity with MDD.

Additional data from personal communication

The lead authors of some studies were con-tacted if required using the provided contact e-mail address. No response was received from the authors of one study (Bankier et al., 2008) who reported GAD prevalence results of 120 patients from a total recruited sample of 143. The GAD prevalence and MDD comorbidity rate were thus derived from the reported cohort of 120. A broad ‘all anxiety disorder’ category was reported in some studies. As the original GAD prevalence data in well-defined CHD groups could not be provided, these studies were excluded.

Statistical analyses

The Mix 1.7 software was employed for data analyses (Bax et al., 2006b); a software descrip-tion was reported by Bax et al. (2006a, 2007). The summation of current and lifetime preva-lence estimates was reported as the proportion of GAD patients within the total CHD sample. Aim 2 data were reported by describing the comorbidity between GAD and MDD (propor-tion of GAD patients with depression) and the comorbidity between MDD and GAD (propor-tion of depressed patients with GAD). Aim 1 and Aim 2 prevalence data were reported as proportions with 95 per cent CI calculated via the Wilson score method without continuity correction (Newcombe, 1998). To report GAD and MDD comorbidity rates, the r value was calculated (Rutledge and Loh, 2004), and then a standardized conversion to Fisher’s Z with standard error was applied (Field, 2001). Correlation effect sizes can be interpreted according to Cohen’s criteria (Cohen, 1992):

small < .10, medium = .10 to <.30, large = .30 to .50. Heterogeneity statistics were evaluated; I2 > 50 per cent in fixed-effects analyses repre-sents considerable heterogeneity, while in ran-dom effects models, when τ2 approaches zero, there is no homogeneity (Tak et al., 2010). When Aim 1 and 2 data were pooled together with a fixed-effects model, the inverse variance approach was selected. In the random effects models for Aim 1–Aim 2 data, the DerSimonian–Laird method (1986) was employed to provide a more conservative estimate of effect size (Tak et al., 2010). To evaluate the presence of publi-cation bias, the fail-safe N was reported, along with Begg and Mazumdar’s (1994) and Egger et al.’s (1997) tests.

Results

GAD prevalence in CHD

There were 12 studies (total N = 3485) reporting GAD prevalence among populations with docu-mented CHD. The Heart and Soul study recruited the largest sample, reporting GAD prevalence among 1015 stable CHD patients (Martens et al., 2010). A Canadian study recruited 804 stable coronary artery disease (CAD) patients (Frasure-Smith and Lesperance, 2008). An Australian study performed structured interviews 4 days after acute coronary syndrome among 436 patients (Parker et al., 2011). A primary care sample reported GAD prevalence rates for 245 patients with MI or heart failure (Sherbourne et al., 1996). Others reported prevalence among CHD patients attending cardiac rehabilitation (Todaro et al., 2007), an outpatient cardiology clinic (Bankier et al., 2008) and coronary angi-ography >50 per cent stenosis (Valkamo et al., 2003). The only CABG surgery study performed structured interview before surgery (Tully et al., 2011). Another report compared MI patients with stroke and spinal cord lesions, reporting MI patients separately (Fedoroff et al., 1991). The smallest studies were among 100 CHD patients (Bankier et al., 2004), 98 heart failure patients

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1608 Journal of Health Psychology 18(12)

with left ventricular systolic dysfunction (Haworth et al., 2005) and 86 CHD outpatients (Birket-Smith et al., 2009).

When pooling the GAD prevalence data together, there was evidence of heterogeneity (I2 = 89.17%). When a random effect model was specified, the pooled GAD prevalence was 10.94 per cent (95% CI: 7.8–13.99; z = 7.01, p < .0001; τ2 = .0024), data shown in Figure 2. The fail-safe N statistic indicated that an additional 1051 missing studies would be required to bring the p value from .00 to .05. Neither Begg and Mazumdar’s nor Eggar’s test supported the evi-dence of publication bias. A sensitivity analysis was performed excluding the studies adopting DSM-III-R or earlier criteria. Again, there was evidence of heterogeneity (I2 = 90.09%), and a random effects model from seven prevalence studies supported a 2 per cent higher prevalence and 13.52 per cent pooled prevalence (95% CI: 8.39–18.66; z = 5.16, p < .0001; τ2 = .004). There was no evidence of publication bias from Begg and Mazumdar’s and Eggar’s test. The fail-safe N statistic indicated that an additional 394 miss-ing studies would be required to bring the p value from .00 to .05.

Lifetime GAD prevalence

Three studies reported lifetime GAD in CHD, and the combined N was 884 patients (Parker et al., 2011; Sherbourne et al., 1996; Todaro et al., 2007). Due to heterogeneity (I2 = 60.89%), a random effects model was specified and showed that the pooled lifetime GAD prevalence was 25.80 per cent (95% CI: 20.84%–30.77%; z = 20.67, p < .001; z = 10.19, p < .0001; τ2 = .0012). There was no evidence of publication bias from Begg and Mazumdar’s or Eggar’s test, and the fail-safe N statistic indicated that an additional 216 missing studies would be required to bring the p value from .00 to .05.

Pooled comorbidity results for depression and GAD in CHD

There were seven studies where the comorbidity between MDD and GAD could be calculated

(N = 2702). One study provided comorbidity rates among a subsample of patients, but not the total recruited sample (Bankier et al., 2008). As there was evidence of heterogeneity (I2 = 97.20%), comorbidity data were pooled together in a random effects model, and this model sug-gested a modest association between MDD and GAD, Fisher’s Z = .30, 95 per cent CI: .19–.42; z = 5.11, p < .001; τ2 = .0228), data shown in Figure 3. There was no evidence of publication bias. The fail-safe N indicated that an additional 1861 missing studies were required to bring the p value from .00 to .05.

Proportion of GAD patients with comorbid depression in CHD

In moderator analyses, only studies reporting the proportion of MDD cases among GAD patients were included (combined N = 2384). As there was evidence of heterogeneity (I2 = 97.77%), comorbidity data were pooled together in a random effects model, which sug-gested a modest association, Fisher’s Z = .28 (95% CI: .10–.46; z = 3.19, p = .0015, τ2 = .0301). There was no evidence of publication bias. The two studies with stable CHD (Frasure-Smith and Lesperance, 2008; Martens et al., 2010) provided a higher comorbidity associa-tion in random effects model (Fisher’s Z = .34, 95% CI: .01–.69; z = 1.97, p = .05, τ2 = .0605) than the acute coronary syndrome studies (Fedoroff et al., 1991; Parker et al., 2011) (Fisher’s Z = .21, 95% CI: −.14 to .58; z = 1.19, p = .23, τ2 = .0629).

Proportion of depressed patients with comorbid GAD in CHD

The proportion of GAD cases among MDD patients could be determined in three studies (Bankier et al., 2004, 2008; Haworth et al., 2005). Comorbidity rates ranged between 18.33 per cent and 61.54 per cent. A random effects model was specified (I2 = 96.35%), and this test showed modest comorbidity between MDD and GAD (Z = .32, 95% CI: .13–.52; z = 3.2985,

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Tully and Cosh 1611

p < .0001). There was no evidence of publica-tion bias from Begg and Mazumdar’s and Eggar’s test. The fail-safe N indicated that an additional 391 missing studies were required to bring the p value from .00 to .05.

Discussion

This systematic review was the first to quan-tify the degree of overlap between categorical depression and anxiety disorders in CHD patients with meta-analysis techniques. The results suggested approximately 11 per cent–14 per cent GAD prevalence in CHD samples, dependent on the diagnostic criteria employed to determine psychiatric disorder status. This finding approximates previous MDD preva-lence estimates of 15 per cent in CHD samples (Thombs et al., 2008). The pooled lifetime GAD prevalence was 26 per cent. Generally speaking, the pooled comorbidity data showed correla-tions in the small to modest range (Cohen, 1992) between MDD and GAD and, thus, each psychiatric disorder is best conceptualized as sharing small to moderate variance in CHD populations.

The low comorbidity rates in CHD patients reported here noticeably contrast with those reported in clinical psychiatric samples. Evidence from three national epidemiological surveys in the Netherlands, United States and Australia (total N = 29,014) showed that GAD shared more variance with the mood disorders (r = .65) than with the other anxiety disorders (range r = .42–.58) in weighted analyses (Watson, 2009). A possible explanation for the discrepancy in comorbidity rates includes that the phenomenology of MDD in cardiovascular patients is discrepant from non-cardiovascular MDD, as previous authors have questioned (Carney and Freedland, 2012). For example, results from the Sequenced Alternatives to Relieve Depression showed that patients with CHD reported more symptoms of sympathetic nervous arousal (Fraguas et al., 2007). However, contrasting results have been reported as to whether a particular cardiovascular depression

subtype might be associated with CHD morbid-ity (Carney and Freedland, 2012; Hoen et al., 2010; Tully et al., 2011).

Indeed, it is also plausible that the phenome-nology of GAD is dissimilar among CHD patients. That said, Hoehn-Saric et al. (2004) reported that GAD patients without documented CHD scored significantly higher on cardiovas-cular and respiratory anxiety symptoms than other psychiatric patients and suggested that such symptoms were markers for somatic focussed worry in GAD. Challenging that ill-ness worry and fear would be significantly ele-vated in CHD patients, Marker et al. (2008) reported that persons without documented ath-erosclerosis scored significantly higher on a measure of heart focussed worry/fear than per-sons with heart disease. Similarly, a Swedish sample of 767 chronic stable angina patients found evidence for lower worries about the future among persons with MI history than those without MI history (25% vs 37%, p < .01) (Billing et al., 2000). Comparably, lower wor-ries were also found for persons with a heart failure diagnosis than persons without heart fail-ure (26% vs 36%, p < .01) (Billing et al., 2000).

As the pooled correlation between MDD and GAD was modest, these findings have implica-tions for interpretation of previous prognostic studies that have inferred heightened CHD mor-bidity risk to MDD and/or GAD. At the very least, findings here do not suggest that studies reporting prognostic CHD risk are merely con-founded by a large degree of shared variance between MDD and GAD. With respect to prog-nostic studies examining MDD and GAD con-currently, the Heart and Soul study showed that GAD increased the risk for subsequent major cardiovascular events between 61 per cent and 74 per cent, while MDD impacted the strength of this association by less than 5 per cent, cor-roborating independence of these psychiatric disorders (Martens et al., 2010). Also, Frasure-Smith and Lesperance (2008) showed that both MDD and GAD were associated with a twofold increased risk for major adverse cardiovascular outcome. However, the authors also noted that a

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1612 Journal of Health Psychology 18(12)

diagnosis of either MDD or GAD conferred the greatest cardiovascular morbidity event risk, despite the small correlation between psychiat-ric disorders in the sample (Fisher’s Z = 17, p = .04). As such, it is not known whether MDD and GAD work through similar or discrepant biobe-havioural mechanisms to portend greater CHD morbidity risk. Curiously, despite low comor-bidity rates in CHD, both MDD and GAD have been associated with reduced vagal control and autonomic nervous system activity (Brosschot et al., 2006). Additionally, previous research links both MDD and GAD to CHD risk factors such as smoking, alcohol use, lower exercise and lower medication adherence (Barger and Sydeman, 2005; Grant et al., 2004; Martens et al., 2010; Wiltink et al., 2011).

Collectively, a sparse number of studies met the inclusion criteria, suggesting that further GAD research is required in CHD to clarify these preliminary findings. Dugas et al. (2010) highlighted the low rate of publications and concluded that GAD research continues to lag behind the other anxiety disorders. In CHD, previous research and intervention efforts appear to have consolidated depression as the predominant psychosocial factor (Denollet, 2008), whereas GAD research is seemingly in the nascent stages. For example, few of the CHD studies reported here investigated prog-nostic cardiovascular outcomes (Frasure-Smith and Lesperance, 2008; Martens et al., 2010; Parker et al., 2011) or receiver operating char-acteristic evaluations of self-report measures to identify GAD (Frasure-Smith and Lesperance, 2008; Haworth et al., 2005; Tully and Penninx, 2012). As other systematic reviews have shown, GAD is a chronic and disabling condition that deleteriously impacts upon quality of life (Bereza et al., 2009), with significant unmet needs (Sherbourne et al., 1996) and associated financial costs in primary care (Hoffman et al., 2008). Thus, given the relatively modest comor-bidity rates between GAD and MDD, the rec-ommendation for further GAD research in CHD cannot be understated. The predominance of CHD research concerning non-specific

self-reported anxiogenic constructs such as trait and state anxiety may hamper efforts to exam-ine specific disorders such as GAD. It was the case here that studies were excluded because various anxiety disorders were collapsed together into an ‘any anxiety disorder category’ that is not clinically informative in cardiac set-tings (Tully and Baker, 2012). In fact, such research practices neglect the heterogeneous presentation of anxiety disorders and the phe-notypic variance that makes each disorder rela-tively unique (Watson, 2009).

This study is presented with several strengths including the systematic data retrieval and meta-analyses techniques to provide a novel quanti-fication of the degree of overlap between depression and anxiety disorders that confer CHD risk. Studies prone to bias with samples fewer than 50 and those adopting self-reports of CHD were excluded. A large proportion of total variance was explained by heterogeneity in the studies, and one potential explanation was the types of CHD patients recruited. For example, only one study was identified among CABG surgery (Tully et al., 2011), one among cardiac rehabilitation attendees (Todaro et al., 2007) and two studies after acute coronary syndrome (Fedoroff et al., 1991; Parker et al., 2011). Other potential sources of heterogeneity include the type of diagnostic criteria to determine GAD, gender ratio and age of patients. A limita-tion concerns the categorical classification of depression and anxiety when these negative emotional constructs are known to reflect a con-tinuum, and critically appraised as potentially reflecting a single disorder (Mennin et al., 2008). Further research might investigate the overlap between MDD and GAD with continu-ous self-report measures that match diagnostic criteria (e.g. patient health questionnaire (PHQ)-9 and GAD-7) (Kroenke et al., 2010), and could pool together r values using a similar methodology to that outlined here.

In conclusion, these data approximate 11 per cent–14 per cent current and 26 per cent life-time GAD prevalence in CHD. The pooled data showed small to modest correlations between

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Tully and Cosh 1613

MDD and GAD and, thus, each psychiatric dis-order is best conceptualized as sharing moder-ate amount of variance in CHD populations. These findings support that GAD and MDD each contribute unique variance to CHD prog-nosis and may assist interpretations of the extant literature.

FundingThis research received no specific grant from any funding agency in the public, commercial or not-for-profit sectors.

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