SS

SMR

a

ARRAA

KPEPDCS

1

slfdaifG2

bEccm

Bf

h0

Journal of Anxiety Disorders 32 (2015) 73–80

Contents lists available at ScienceDirect

Journal of Anxiety Disorders

ubthreshold and threshold DSM-IV generalized anxiety disorder iningapore: Results from a nationally representative sample

iau Pheng Lee ∗, Vathsala Sagayadevan, Janhavi Ajit Vaingankar, Siow Ann Chong,ythily Subramaniam

esearch Division, Institute of Mental Health, Singapore

r t i c l e i n f o

rticle history:eceived 8 October 2014eceived in revised form 16 March 2015ccepted 18 March 2015vailable online 28 March 2015

eywords:opulation-based surveypidemiology

a b s t r a c t

Previous nationally representative studies have reported prevalence of DSM-IV generalized anxiety dis-order (GAD). However, subthreshold and threshold GAD expressions remain poorly understood. Thecurrent study examined the prevalence, correlates and co-morbidity of a broader diagnosis of GAD inSingapore. The Singapore Mental Health Study (SMHS) was an epidemiological survey conducted in thepopulation (N = 6616) aged 18 years and older. The Composite International Diagnostic Interview version3.0 (CIDI 3.0) was used to establish mental disorder diagnoses. The lifetime prevalence for subthresholdGAD (2.1%) and threshold GAD (1.5%) in the current sample was found to be lower than in Westernpopulations. Younger age group, Indian ethnicity, previously married, chronic physical conditions, and

revalenceisabilityomorbidityingapore

being unemployed were associated with higher odds of having more severe expression of generalizedanxiety. The relatively lower prevalence rate of subthreshold GAD expression suggests possible culturalinterferences in the reporting and manifestation of anxiety symptomatology. Despite the low preva-lence, significant impacts on functioning and comorbidity among subthreshold generalized anxiety casesindicate the importance of early treatment to ensure a better prognosis.

. Introduction

Generalized anxiety disorder (GAD) is characterized by exces-ive, persistent worry and anxiety lasting for a duration of ateast 6 months, accompanied by symptoms, such as restlessness,atigue, poor concentration, irritability, muscle tension, and sleepisturbances causing substantial distress and impairment in dailyctivities (APA, 1994, 2013). In addition, the waxing and wan-ng symptomology that changes from subthreshold syndromes toull symptomatic GAD is common among GAD sufferers (Angst,amma, Baldwin, Ajdacic-Gross, & Rössler, 2009; Ballenger et al.,001).

Diagnosing GAD poses significant challenges given the relativelyroad range of prevalence estimates reported across countries.ven among community studies which utilized similar diagnostic

riteria, instruments, and sampling methods, the prevalence variesonsiderably. For instance, the lifetime prevalence was 0.8% inetropolitan China and 2.3% in Korea, as opposed to 5.7% in United

∗ Corresponding author at: Research Division, Institute of Mental Health, 10uangkok View, Singapore 539747, Singapore. Tel.: +65 6389 3623;

ax: +65 6389 2795.E-mail address: siau pheng lee@imh.com.sg (S.P. Lee).

ttp://dx.doi.org/10.1016/j.janxdis.2015.03.008887-6185/© 2015 Elsevier Ltd. All rights reserved.

© 2015 Elsevier Ltd. All rights reserved.

States and 6.0% in New Zealand (Cho et al., 2007; Kessler, Berglund,et al., 2005; Lee, Tsang, Zhang, et al., 2007; Oakley Browne, Wells,Scott, & Mcgee, 2006). The observed differences in prevalenceestimates across different cultures raise issues with regard tocross-cultural variability in psychiatric epidemiology. The lack ofmeasurement equivalence of the instrument, incapability of thediagnostic criteria to identify pathology across cultures, or a truedifference of prevalence rate among different cultural groups havebeen suggested as possible mechanisms underlying the observeddifferences (Asnaani, Richey, Dimaite, Hinton, & Hofmann, 2010;Lewis-Fernández et al., 2011).

In addition, constant revisions of the diagnostic criteria acrossthe various versions of Diagnostic and Statistical Manual of MentalDisorders (DSM) reflect uncertainty in the definition and diagno-sis of GAD, and further increase the complexity of the matter (Leeet al., 2009). Increase in the duration of “worrying” from 1 monthto 6 months in DSM-III-R, was made in an effort to differentiatea transient anxiety response to stress from GAD. The subsequentversion of the manual, DSM-IV, again redefined GAD, additionallystipulating that a) the anxiety and worry must be excessive, b) the

worry must be difficult to control, and c) autonomic symptomswere replaced by at least three of the six key hypervigilance/tensionassociated symptoms from the diagnostic criteria (Beesdo-Baumet al., 2011; Carter, Wittchen, Pfister, & Kessler, 2001).

7 xiety

itmeLdfdiecitprie

bs(elti(

2

2

i6saiRwrfnead

(nipaagwacop

2

vu

4 S.P. Lee et al. / Journal of An

Such changes in the DSM-IV GAD diagnostic criteria have madet more difficult for individuals to be diagnosed with GAD. Yet, evenhose with subthreshold level of generalized anxiety expressions

ay also suffer from significant impairment, pathological anxi-ty, and comorbid conditions (Carter et al., 2001; Haller, Cramer,auche, Gass, & Dobos, 2014). For instance, increasing the requireduration of worry precludes individuals experiencing symptomsor less than 6 months from receiving a diagnosis. However, evi-ence suggests that this group of cases also show significant daily

mpairment (Kessler, Brandenburg, et al., 2005), similar to levelsxperienced by individuals who have met the 6-month durationriterion (Lee et al., 2009). Thus, these diagnostic changes impactndividuals with subthreshold symptoms as they may not receivehe clinical attention they need. Furthermore, the relatively highrevalence of subthreshold GAD across epidemiological samples,anging from 3.6% to 13.7%, underscores the importance of enhanc-ng our understanding of the implications of such changes (Cartert al., 2001; Haller et al., 2014).

Despite their disabling characteristics, and significant diseaseurden, the nature of milder forms of generalized anxiety expres-ions remains poorly understood, particularly in an Asian contextLee et al., 2009). Given the urgency to understand the disorderpidemiology, this paper aimed to assess the prevalence of variousevels of generalized anxiety expressions, as well as their rela-ionship to comorbid conditions, socio-demographic factors, andmpairment, using the data from the Singapore Mental Health StudySMHS).

. Method

.1. Sample

The SMHS was a nationwide epidemiological survey conductedn Singapore from December 2009 to December 2010. A total of616 respondents, aged 18 years and older were recruited in theurvey. Disproportionate stratified sampling was used to obtainn equivalent proportion of 30% of the three main ethnic groupsn Singapore (Chinese, Malay, and Indian) in the current sample.espondents were randomly selected from a national database, andere approached at their households for face-to-face interviews. A

esponse rate of 75.9% was achieved in the study. No significant dif-erences were found in age and gender between respondents andon-responders. However, Chinese and those belonging to otherthnic groups were more likely to be non-responders than Malaysnd Indians. Detailed methodology of the current survey has beenescribed in a prior article (Subramaniam et al., 2012).

The weighted mean age of respondents was 43.9 yearsS.E. = 0.3). Weighted distribution by ethnic group was 76.9% Chi-ese, 12.3% Malay, 8.3% Indian, and 2.4% Other ethnicities, which

s representative of the Singapore population based on the 2007opulation census. Fifty-two percent of respondents were female,nd 48.5% were male. The majority of respondents were marriedt the time of the survey (62.4%), 28.9% of respondents were sin-le, 4.2% were divorced/separated, and 4.4% of respondents wereidowed. In addition, the majority of respondents had completed

t least secondary level education (secondary, 27.6%; Pre-U/juniorollege/diploma, 22.4%; vocational, 7.9%; university, 22.4%), 14.7%f respondents had primary level education, and 5.5% had pre-rimary level education.

.2. Instruments

The SMHS used the Composite International Diagnostic Inter-iew version 3.0 (CIDI v3.0) as the main survey instrument. These of CIDI requires completion of a training program offered by

Disorders 32 (2015) 73–80

the WHO-CIDI Training and Research Center. Study team memberswho attended the training program conducted an intensive 3-weektraining program for lay interviewers.

CIDI v3.0 was adapted to the Singaporean context. Other thanthe English version, the study also used the Malay and Chineseversions of the instrument. The Malay language (Bahasa Melayu)version of CIDI was fully translated by the study team, whereasthe Chinese language version was adapted from a version trans-lated by the WMH-CIDI group in China. We did not develop aTamil version, the major language spoken by Indians in Singapore,as we made the assumption that most Indians are conversant inEnglish (Department of Statistics, Ministry of Trade and Industry,Singapore, 2013). Respondents chose the language (i.e. English, Chi-nese, Malay) in which they were most comfortable to complete thesurvey.

Three screening questions prefaced the GAD module: (1) “Didyou ever have a time in your life when you were a “worrier” – thatis, when you worried a lot more about things than other peoplewith the same problems as you?,” (2) “Did you ever have a time inyour life when you were much more nervous or anxious than mostother people with the same problems as you?,” and (3)“Did you everhave a period lasting one month or longer when you were anxiousand worried most days?” Respondents who answered “yes” for atleast one of the screening questions proceeded to the GAD module.If respondents answered “no” to all three screening questions, theGAD module was skipped.

Diagnoses of mental illnesses reported in this paper wereapplied without using DSM-IV hierarchy exclusion rules, unlessstated otherwise. Chronic physical conditions were assessed usinga modified version of the CIDI chronic physical condition check-list. All respondents completed the 30-day functioning modulein the CIDI and the EQ-5D questionnaire. The EQ-5D question-naire measures various aspects of health-related quality of life,including mobility, self-care, usual activities, pain/discomfort, andanxiety/depression.

2.3. Assessment of DSM-IV generalized anxiety disorder andsubthreshold expressions

The GAD module in the CIDI starts with a checklist of types ofworries. Assessment of DSM-IV GAD is described in Table 1. A skip-ping pattern was applied depending on respondents’ responses tothe items.

Levels of generalized anxiety expressions included (a) worryingfor at least 1 but less than 3 months, (b) worrying for at least 3but less than 6 months, (c) subthreshold GAD, and (d) thresholdGAD. Respondents who reported worrying for at least 3 monthsand had at least 2 of the other DSM-IV GAD criteria (B, C, or E),were classified as “subthreshold GAD,” whereas respondents whoreported at least 6 months of worrying and met criteria B, C, andE were considered “threshold GAD” cases. These criteria were firstused in Carter et al.’s (2001) study, and are used here to facilitatecross-cultural comparisons.

A DSM-IV GAD diagnosis also contains two exclusion criteria.Criterion D stipulates that the focus of the worry and anxiety shouldnot be confined to features of another Axis I disorder, whereascriterion F states that the anxiety must not be due to the direct phys-iological effects of substance use, medical conditions, or other mooddisorders. Respondents only received a DSM-IV GAD diagnosis ifthey met the abovementioned criteria.

2.4. Statistical analysis

Statistical analysis was performed using the Statistical Anal-ysis Software (SAS) System version 9.3 (SAS Institute, Cary, NC)and Stata statistical software version 13.0 (StataCorp, College

S.P. Lee et al. / Journal of Anxiety Disorders 32 (2015) 73–80 75

Table 1Assessment of DSM-IV Generalized Anxiety Disorder in Composite International Diagnostic Interview (CIDI) version 3.0.

Criteriona Fulfilled if. . . The subsequent items of GAD modulewere skipped if. . ..b

Criterion A part 1Excessive anxiety and worry

‘Yes’ to either one of 3 screening questions in thescreening module

‘No’ to all three screening questions

Criterion A part 3Anxiety about a number of events oractivities

Endorsed worry for more than one type ofevent/activity (e.g. finances, physical appearanceand etc.)

Criterion DWorry and anxiety is not confined toanother Axis 1 disorder

Endorsed worry to items not related to mentalhealth, substance use, phobic and obsessivecompulsive situations, separation anxiety issue

Endorsed only one specific type ofworry

Criterion BDifficult to control the worry

‘Often’ or ‘Sometimes’ in how often they haddifficulty in controlling their worry

Criterion A part 2Anxiety occurring more days thannot for at least 6 months

Reported ‘Six months or longer’ as the longestperiod when they were anxious on most days

‘Less than one month’ reported

Criterion CAssociated key symptoms

Endorsed at least three or more of the six keysymptoms (i.e. restlessness, easily fatigued,difficulty concentrating, irritability, muscletension, sleep disturbance)

Endorsed less than two key symptoms(i.e. 0 or 1 symptom)

Criterion E part 1Cause distress

Endorsed emotional distress they experienced, orendorsed they could not think about anythingbecause of the worry

Criterion E part 2Cause impairment in functioning

Endorsed worry interfered with work, social life,personal relationship, or ability to carry dailyactivities, or as reflected in Sheehan DisabilityScale.

Did not endorse distress andimpairment that caused by their worryor anxiety

Criterion F part 1Worry and anxiety is not due tophysiological effects of a substanceor other medical conditions

Did not endorse worry to be due to physical causes(e.g. physical illness, injury), or use of medication,drugs, or alcohol

Criterion F part 2Worry and anxiety is not due toother mood disorders

No comorbidity of mood disorders as reflected indiagnosis in respective disorder specific CIDImodule, or with any comorbid of mood disorderswhile GAD age of onset is younger, age of recencyis older (i.e. more recent), duration of persistenceis longer than other mood disorders

I GADg.

SasomaisatigcAlbtf

3

3

adm

a Criteria fulfillment is presented in accordance with sequence of items in the CIDb Unless as stated in the table, the subsequent items were asked without skippin

tation, TX). The data was weighted to adjust for oversampling,nd post-stratified by age and ethnicity distribution between theurvey sample and Singapore population. Worrying for less thanne month, worrying for at least 1 month, worrying for at least 3onths, subthreshold GAD, and threshold GAD were organized into

single 5-level ordinal variable with subsequent points on the scalendicating increasing severity level of generalized anxiety expres-ion (i.e. threshold GAD is more severe than subthreshold GADnd etc.). Ordinal logistic regression was performed to examinehe association between the various levels of generalized anx-ety expressions and socio-demographic factors (including ageroup, ethnicity, gender, marital status, education level, presence ofhronic physical conditions, employment status, and income level).fter adjusting for age group, gender, and ethnicity, multivariate

ogistic regression was used to calculate the odds ratios for comor-idity and impairment. Poisson regression was used to calculatehe rate ratios of functioning days lost using data from the 30-dayunctioning module.

. Results

.1. Prevalence of worrying and GAD

Prevalence estimates for the different levels of generalizednxiety expressions are presented in Table 2. Among the respon-ents, 5.7% reported worrying for at least one month (inclusive ofore severe levels), 3.7% reported worrying for at least 3 months

specific module.

(inclusive of subthreshold GAD and threshold GAD), 2.1% had sub-threshold GAD (inclusive of threshold GAD), and 1.5% had thresholdGAD. After applying DSM-IV hierarchy exclusion rules, 0.9% ofrespondents received a DSM-IV GAD diagnosis.

Table 2 shows the association between generalized anxi-ety expressions and socio-demographic variables. Being younger,Indian, of “Other” ethnicities, divorced/separated, widowed, andunemployed significantly predicted more severe levels of general-ized anxiety expressions. Those with primary education were lesslikely to have more severe generalized anxiety expressions thanthose with university education.

3.2. Comorbidity and impairment of worrying and GAD

Table 3 shows the prevalence and odds ratios for comorbidityof lifetime mental illnesses and chronic physical conditions. Themajority of respondents who worried for at least one month or hadmore severe levels of expressions (79.3%) had at least one of thedisorders listed in Table 3. Prevalence of comorbid chronic physi-cal conditions was higher than that of comorbid mental illnessesacross all generalized anxiety expressions, except the thresholdGAD category (any physical conditions, 49.4%; any mental illnesses,

78.8%). Major depressive disorder (MDD) was found to be the mostcommon comorbid mental illness, and chronic pain was the mostcommon physical condition across the generalized anxiety expres-sions.

76 S.P. Lee et al. / Journal of Anxiety Disorders 32 (2015) 73–80

Table 2Socio-demographic association with levels of generalized anxiety expressions.

Worrying ≥1 montha

5.7% (1.9%)Worrying ≥ 3months 3.7% (1.6%)

Subthreshold GAD2.1% (0.6%)

Threshold GAD1.5% (1.5%)

Odds ratiosb

n % 95% CI n % 95% CI n % 95% CI n % 95% CI OR 95% CI p-Value

Age group18–34 82 3.17 2.2 4.1 43 2.27 1.4 3.1 27 0.79 0.3 1.2 53 1.76 1.1 2.4 135–49 39 1.47 0.8 2.1 37 1.68 0.9 2.4 19 0.87 0.3 1.4 48 1.95 1.2 2.8 0.7 0.5 1.2 0.250–64 24 1.28 0.5 2.1 13 0.65 0.1 1.2 10 0.34 0.0 0.7 21 1.22 0.4 2.0 0.4 0.2 0.8 0.007*

65 + + 3 1.26 0.0 2.9 6 1.42 0.0 3.1 0 – – – 0 – – – 0.3 0.1 0.9 0.03*

EthnicityChinese 37 1.79 1.2 2.4 33 1.61 1.1 2.2 11 0.52 0.2 0.8 29 1.37 0.9 1.9 1.0Malay 43 1.80 1.3 2.3 28 1.18 0.7 1.6 17 0.70 0.4 1.0 35 1.45 1.0 1.9 1.0 0.7 1.4 1.0Indian 58 2.93 2.2 3.7 27 1.37 0.8 1.9 23 1.17 0.7 1.6 53 2.63 1.9 3.3 1.5 1.1 2.0 0.004*

Other 10 4.18 1.6 6.8 11 4.32 1.7 6.9 5 1.60 0.1 3.1 5 2.09 0.2 4.0 1.8 1.1 3.1 0.03*

GenderMale 87 2.38 1.7 3.1 58 1.85 1.2 2.5 23 0.43 0.2 0.7 48 1.22 0.7 1.7 1.0Female 61 1.53 1.0 2.1 41 1.37 0.8 2.0 33 0.81 0.4 1.2 74 1.78 1.2 2.4 1.0 0.7 1.4 0.9

Marital statusSingle 59 3.08 2.0 4.1 28 1.47 0.7 2.2 21 0.89 0.3 1.4 37 1.48 0.8 2.2 1.0Married 78 1.45 1.0 2.0 57 1.27 0.8 1.7 32 0.51 0.2 0.8 66 1.21 0.8 1.7 0.9 0.6 1.5 0.8Divorced/separated 8 1.65 0.0 3.5 10 4.94 1.3 8.6 2 1.00 0.0 2.8 17 7.42 2.9 11.9 4.5 2.4 8.4 <0.001**

Widowed 3 1.66 0.0 4.6 4 4.03 0.0 8.4 1 0.12 0.0 0.4 2 0.18 0.0 0.4 3.3 1.2 8.8 0.02*

Education levelUniversity 39 2.32 0.0 0.3 27 2.71 1.5 3.9 9 0.38 0.0 0.8 22 1.40 0.6 2.2 1.0Pre-U/Junior College/Diploma 33 2.61 0.1 1.6 23 1.78 0.8 2.7 12 0.67 0.1 1.2 39 2.39 1.3 3.5 1.0 0.6 1.5 0.9Vocational 22 3.64 0.7 2.4 12 1.52 0.2 2.8 10 2.23 0.4 4.0 8 0.51 0.2 0.9 1.0 0.5 1.8 0.9Secondary 39 1.56 1.5 3.7 22 0.82 0.3 1.4 18 0.67 0.2 1.1 35 1.62 0.8 2.4 0.7 0.4 1.3 0.3Primary 13 0.84 1.5 5.8 12 0.64 0.1 1.2 5 0.14 0.0 0.3 17 1.17 0.3 2.0 0.4 0.2 0.9 0.04*

Pre-Primary 2 0.13 1.3 3.3 3 3.08 0.0 6.6 2 0.18 0.0 0.4 1 0.06 0.0 0.2 0.5 0.2 1.7 0.3Any chronic physical condition

No 83 1.71 1.2 2.2 40 1.02 0.6 1.4 28 0.57 0.3 0.9 52 1.31 0.8 1.8 1.0Yes 65 2.26 1.4 3.1 59 2.42 1.6 3.3 28 0.71 0.3 1.1 70 1.79 1.1 2.4 2.3 1.7 3.1 <0.001**

Employment statusEmployed 113 2.08 1.5 2.6 70 1.73 1.2 2.3 38 0.52 0.3 0.8 81 1.41 1.0 1.9 1.0Economically inactive 20 1.04 0.3 1.8 20 1.25 0.3 2.2 7 0.27 0.0 0.6 24 1.10 0.4 1.8 0.8 0.5 1.3 0.3Unemployed 10 3.69 0.6 6.7 6 1.28 0.0 2.8 6 2.33 0.0 4.8 14 5.10 1.5 8.7 2.5 1.4 4.5 0.002*

IncomeBelow $19,999 71 1.62 1.0 2.2 46 1.24 0.7 1.8 33 0.62 0.3 0.9 62 1.60 1.0 2.2 1.0$20,000–$49,999 48 2.53 1.6 3.5 31 2.20 1.2 3.2 18 0.92 0.3 1.5 36 1.22 0.6 1.8 1.2 0.8 1.8 0.4Above $50,000 22 2.18 0.9 3.5 17 1.98 0.8 3.1 5 0.35 0.0 0.8 16 1.66 0.6 2.7 0.9 0.5 1.7 0.8

a Prevalence in the parentheses are mutually exclusive with each group, while prevalence out of the parentheses are inclusive of more severe levels.b Based on multivariate ordinal logistic regression, with 5 levels of generalized anxiety expressions as an ordinal outcome.* Significant at p < 0.05 level.

** Significant at p < 0.001 level.

Table 3Prevalence and odds ratios (ORs) of comorbidity of life time DSM-IV mental illnesses, and chronic physical conditions in levels of generalized anxiety expressions.

Comorbid disorder Worrying ≥1 month Worrying ≥ 3 months Subthreshold GAD Threshold GAD

n % ORa 95% CI n % ORa 95% CI n % ORa 95% CI n % ORa 95% CI

Lifetime DSM-IV mental illnessesMajor depressive disorder 40 31.4 9.5 (5.3, 17.0)** 32 32.1 9.8 (5.2, 18.7)** 24 29.9 7.8 (3.4, 17.9)** 73 58.9 30.2 (16.7, 54.6)**

Dysthymia 2 0.5 2.1 (0.4, 9.4) 7 3.8 20.0 (5.0, 79.5)** 1 0.8 2.7 (0.3, 23.2) 13 9.9 38.7 (11.9, 126.1)***

Bipolar disorder 10 5.4 6.6 (2.3, 18.3)*** 1 2.4 2.8 (0.4, 22.0) 6 9.8 11.9 (2.9, 49.2)** 20 21.0 31.5 (13.7, 72.4)**

OCD 14 6.8 2.7 (1.1, 6.5)* 11 11.4 4.9 (2.0, 11.8)** 8 7.4 2.7 (1.1, 6.3)* 26 27.1 13.1 (6.8, 25.3)**

Alcohol abuse 20 17.1 5.2 (2.3, 11.6)** 9 9.2 2.4 (0.9, 6.5) 8 10.8 3.9 (1.2, 12.9)* 9 4.2 1.4 (0.6, 3.1)Alcohol dependence 2 0.5 0.6 (0.1, 2.7) 2 2.4 3.8 (0.5, 27.9) 3 2.3 3.8 (0.9, 16.0) 6 3.1 7.5 (2.9, 19.4)**

Chronic physical conditionsDiabetes 9 2.0 0.3 (0.1, 0.6)** 9 12.7 2.5 (0.9, 7.2) 3 2.2 0.5 (0.1, 1.7) 8 4.4 0.8 (0.3, 2.7)Hypertension 22 19.4 1.6 (0.8, 3.4) 18 16.8 1.2 (0.5, 3.3) 6 9.7 1.0 (0.2, 4.4) 17 18.8 1.8 (0.9, 3.7)Cardiovascular 4 0.8 0.3 (0.1, 1.0)* 5 11.2 6.4 (2.2, 19.0)** 3 1.8 1.5 (0.4, 5.0) 4 3.3 2.1 (0.5, 9.5)Chronic pain 31 21.4 1.9 (1.0, 3.5) 34 38.9 4.3 (2.4, 7.6)** 17 33.9 3.3 (1.4, 7.8)* 46 33.7 3.4 (1.9, 6.0)**

Ulcer 5 4.9 2.9 (0.9, 9.5) 4 3.1 1.6 (0.4, 7.2) 2 1.7 1.0 (0.2, 4.5) 6 4.6 2.7 (0.8, 9.5)Cancer 0 – – – 1 0.3 0.5 (0.1, 3.7) 0 – – – 2 2.8 6.0 (0.9, 40.8)Neurological conditions 4 0.9 0.3 (0.1, 0.9)* 3 2.9 0.9 (0.2, 4.7) 1 0.8 0.3 (0.0, 2.0) 5 5.6 1.8 (0.5, 6.3)Respiratory conditions 24 22.2 2.4 (1.2, 4.6)* 21 23.9 2.8 (1.3, 5.7)* 6 5.4 0.5 (0.2, 1.3) 24 11.8 1.3 (0.7, 2.7)

Any mental illness 62 45.1 7.0 (4.0, 12.4)** 44 45.7 7.3 (4.0, 13.3** 30 39.2 5.45 (2.6, 11.6)** 94 78.8 34.9 (17.8, 68.4)**

Any physical condition 65 48.5 1.7 (1.0, 2.8)* 59 62.9 3.2 (1.8, 5.7)** 28 47.1 1.85 (0.8, 4.2) 70 49.4 1.9 (1.1, 3.2)*

Any of the above disorders 104 73.1 3.9 (2.3, 6.6)** 76 80.6 6.1 (3.1, 12.0)** 44 74.7 4.7 (1.8, 12.5)* 109 87.7 11.1 (4.8, 25.3)**

a Based on multivariate logistic regression, adjusted for age group, gender and ethnicity.* Significant at p < 0.05 level.

** Significant at p < 0.001 level.

S.P. Lee et al. / Journal of Anxiety Disorders 32 (2015) 73–80 77

Table 4Association between functioning and levels of generalized anxiety expressions.

Worrying ≥ 1 month Worrying ≥ 3 months Subthreshold GAD Threshold GAD

OR 95% CI p-Value OR 95% CI p-Value OR 95% CI p-Value OR 95% CI p-Value

Fair/poor self-perceivedmental healtha

4.3 2.4 7.8 <0.001** 3.9 2.0 7.5 <0.001** 7.1 2.9 17.5 <0.001** 12.5 6.7 23.1 <0.001**

Fair/poor self-perceivedphysical healtha

1.2 0.7 2.2 0.5 3.4 2.0 5.8 <0.001** 2.5 1.0 5.9 0.046* 3.9 2.2 7.0 <0.001**

EQ-5Db

Mobility 2.2 0.5 8.7 0.3 1.8 0.3 12.1 0.6 6.6 1.3 34.1 0.02* 3.2 1.0 10.0 0.046*

Self-care 9.5 1.2 75.2 0.03* <0.001 <0.001 <0.001 <0.0001 <0.001 <0.001 <0.001 <0.0001 2.4 0.5 11.5 0.3Usual activities 2.5 0.6 10.8 0.2 3.4 0.7 16.7 0.1 1.6 0.4 7.1 0.5 3.9 1.1 14.6 0.04*

Pain/discomfort 1.4 0.7 3.1 0.4 3.1 1.6 6.1 <0.001** 3.3 1.2 8.8 0.02* 5.6 3.0 10.5 <0.001**

Anxiety/depression 7.7 4.1 14.7 <0.001** 3.5 1.6 7.4 0.001* 8.8 3.2 23.8 <0.001** 13.1 7.3 23.5 <0.001**

a Multivariate logistic regression, adjusted for age group, gender and ethnicity.b Multivariate ordinal logistic regression, adjusted for age group, gender and ethnicity.

hitgopoto

aEanl

3

rwta1acowde

r

TM

* Significant at p <0.05 level.** Significant at p < 0.001 level.

The associations between self-perceived mental health, physicalealth, health-related quality of life, and levels of generalized anx-

ety expressions are presented in Table 4. Compared to the grouphat reported worrying for less than one month, the other levels ofeneralized anxiety expressions showed significantly higher oddsf fair/poor mental health. A similar trend was observed for self-erceived physical health – compared to the “worrying less thanne month” group, those with worrying for at least 3 months, sub-hreshold GAD, and threshold GAD were found to have higher oddsf fair/poor physical health.

Various levels of generalized anxiety expressions were associ-ted with poorer health-related quality of life as reflected by theQ-5D measurement (Table 4). Rate ratios of functioning days lostre shown in Table 5. Subthreshold and threshold GAD were sig-ificantly associated with higher rate ratios of functioning days

ost.

.3. DSM-IV GAD criteria fulfillment

In the current survey, 2.8% of the respondents fulfilled crite-ion A, 10.8% of respondents fulfilled criterion B (difficult to controlorry), 3.9% of respondents fulfilled criterion C (associated symp-

oms), and 8.9% of respondents fulfilled criterion E (impairmentnd disability). Within criterion A, 31.0% of respondents met part

(excessive worry), and 20.0% of respondents met part 3 (worrybout multiple events). However, the low prevalence of 2.8% forriterion A can be ascribed to respondents’ failure to meet part 2f criterion A (worrying duration for at least 6 months). In otherords, although many fulfilled parts 1 and 3 of the criterion, they

id not meet criterion A because the duration of their worry did notxceed 6 months (part 2).

Among the 122 respondents who met threshold GAD criteria, 1espondent did not fulfill criterion D, whereas 50 of them did not

able 5ean, standard error, and rate ratios (RRs) of 30-day functioning across levels of generali

30-day functioning Worrying ≥ 1 month Worrying ≥ 3 months

Mean S.E. RRa 95% CI Mean S.E. RRa 9

Work lost days 1.0 0.6 2.1 (0.7, 7.0) 0.2 0.1 0.4 (0Stay in bed days 0.4 0.2 1.4 (0.6, 3.4) 0.2 0.1 0.5 (0Work cutback days 0.9 0.5 2.0 (0.7, 5.6) 1.6 1.2 3.8 (0Work quality cutback days 0.4 0.2 1.0 (0.4, 2.4) 1.4 1.2 4.1 (0Work effort exertion days 0.8 0.6 2.3 (0.5, 10.8) 0.2 0.1 0.4 (0

a Multivariate poisson regression, adjusted for age group, gender and ethnicity.* Significant at p < 0.05 level.

** Significant at p < 0.001 level.

fulfill criterion F. Overall, 72 respondents (prevalence = 0.9%) metfull DSM-IV GAD diagnostic criteria, after DSM-IV hierarchy andorganic rules were applied.

4. Discussion

Prevalence of DSM-IV GAD and various levels of generalizedanxiety expressions were relatively low in the current sample,compared to prevalence estimates in Western samples. Amongrespondents, 5.7% reported worrying for at least one month, 3.7%reported worrying for at least 3 months, 2.1% met criteria for sub-threshold GAD, 1.5% met criteria for threshold GAD, and 0.9% ofrespondents met full criteria for DSM-IV GAD. Rates in our samplediffered from those reported by Carter et al. (2001) in their Germansample, in which they observed a rate of 7.8% for worrying at least1 but less than 3 months, 4.1% for worrying at least 3 but less than6 months, 3.6% for subthreshold GAD, and 1.5% for DSM-IV GAD.However, it is to note that their finding was based on 12-monthprevalence, whereas observation in the current sample was basedon life time prevalence.

The prevalence of DSM-IV GAD has been found to be lowerin Asian samples than in Western samples (Michael, Zetsche, &Margraf, 2007). For example, the National Comorbidity Study Repli-cation by Kessler, Berglund, et al. (2005) in the United Statesreported a lifetime prevalence of DSM-IV GAD of 5.7%. In contrast,Lee, Tsang, Zhang, et al. (2007) reported a lifetime prevalence of0.8% in metropolitan China, and Cho et al. (2007) found a life-time prevalence of 2.3% in South Korea. Furthermore, Asnaani et al.(2010) found that Asian Americans were less likely to receive a

DSM-IV GAD diagnosis than White Americans. The lower preva-lence of GAD among Asian respondents might be due to severalreasons, such as the true prevalence in the sample, an insensitivediagnostic instrument, or a different manifestation of symptoms

zed anxiety expressions.

Subthreshold GAD Threshold GAD

5% CI Mean S.E. RRa 95% CI Mean S.E. RRa 95% CI

.1, 1.2) 1.4 0.9 3.2 (0.9, 11.3) 1.3 0.4 2.9 (1.5, 5.6)*

.2, 1.4) 1.0 0.4 3.8 (1.5, 9.6)* 0.6 0.2 2.3 (1.1, 5.0)*

.8, 17.9) 3.2 1.8 7.2 (2.4, 21.6)** 1.8 0.6 4.1 (2.2, 7.6)**

.7, 22.8) 1.1 0.5 3.3 (1.5, 7.3)* 1.7 0.6 5.0 (2.5, 10.0)**

.1, 1.4) 1.7 0.5 4.9 (2.6, 9.2)** 1.1 0.3 3.0 (1.8, 5.88)**

7 xiety

aM

teSittos2tmwtatotTAaswrlwmlrm(

tcfiHacAmej

tbrdateep(rsbfsa

seAi

8 S.P. Lee et al. / Journal of An

cross cultures (Asnaani et al., 2010; Lewis-Fernández et al., 2011;ichael et al., 2007; Sue & Sue, 1987).As the structure of the CIDI adheres closely to DSM-IV diagnos-

ic criteria, it may fail to assign a diagnosis to participants whosexperiences do not conform to its diagnostic assumptions (Sue &ue, 1987), especially since the screening stage of the DSM-IV GADmmediately rules out many individuals – even if they show symp-oms of anxiety – without examination of other criteria. This inurn prevents one from determining the extent to which culturalr other possible elements interfere with manifestations of GADymptoms (Lee, Tsang, Chui, et al. 2007; Lewis-Fernández et al.,011; Liao et al., 2012). For example, screening questions precedinghe GAD module ask respondents whether they are worried about

ore things or are much more anxious/nervous than other peopleith the same problem as them. Having to compare themselves

o “other people” as a means of evaluating the state of their ownnxiety can be problematic for Asian respondents as Asian culturesend to be more interdependent and collectivistic than Westernnes (Lalwani, Shavitt, & Johnson, 2006). Thus, they might be reluc-ant to admit that their state differs from that of other individuals.he strong ‘group’ perspective may partly result in the difficultiessians have in comparing oneself at an individual level. Asians maylso be more reluctant to report their psychological distress to atranger (i.e. interviewer) due to social stigma strongly associatedith mental illnesses (Chong et al., 2012). In addition, previous

esearch suggests that Asians are more likely to somaticize psycho-ogical distress (Hoge et al., 2006). Hence, prioritizing psychological

orry over associated somatic symptoms in the CIDI GAD moduleight exclude respondents with atypical presentations of patho-

ogical anxiety (Lewis-Fernández et al., 2011). Shifting questionselated to somatic symptoms to the start of diagnostic moduleay improve accuracy of prevalence estimates in Asian samples

Guarnaccia, 1997; Michael et al., 2007).Approximately one tenth (10.8%) of respondents endorsed cri-

erion B (difficult to control worry) of the DSM-IV GAD diagnosticriteria, and a comparable percentage (8.9%) of respondents ful-lled criterion E (anxiety/worry caused impairment and distress).owever, a relatively low prevalence was noted for criteria C (3.9%)nd A (2.8%). The low prevalence observed for criterion A indi-ated that very few met the duration of 6 months for worrying.lthough researchers have argued for the validity of the 6-monthinimum duration of worry (Kessler, Brandenburg, et al. 2005; Lee

t al., 2009), Ruscio (2002) posited that both criteria A and E – notust criterion A – best differentiated high worriers from GAD cases.

The prevalence of respondents who endorsed each criterion inhe current sample was relatively low compared to the findingsy Hobbs, Anderson, Slade, and Andrews (2014) among Australianespondents. However, previous studies have consistently shownifferences in the endorsement pattern of DSM-IV GAD criteriacross cultures, particularly with regard to the associated symp-oms criterion (criterion C) (Hoge et al., 2006; Lee, Tsang, Chui,t al., 2007; Lewis-Fernández et al., 2011). For example, Hoget al. (2006) found that Asian respondents were more likely toresent distress in somatic form, while Lee, Tsang, Chui, et al.2007) found that respondents in their Hong Kong sample whoeceived a GAD diagnosis were also more likely to endorse somaticymptoms not mentioned in the DSM-IV criteria (e.g. difficultyreathing, palpitations, sweating) than threshold GAD cases. Thus,uture research should focus on elucidating the list of associatedymptoms included in a DSM-5 GAD diagnosis, especially whenpplying DSM criteria to non-Western cultures.

Consistent with past studies, marital status and employment

tatus were significant risk factors for more severe levels of gen-ralized anxiety expressions (Grant et al., 2005; Hunt, Issakidis, &ndrews, 2002; Lieb, Becker, & Altamura, 2005). However, diverg-

ng from prior research that has found GAD to be more common

Disorders 32 (2015) 73–80

among older age groups (Carter et al., 2001; Haller et al., 2014),younger age predicted more severe levels of generalized anxietyexpressions in the present investigation. This discrepancy couldbe due to higher mental health literacy among younger respon-dents (Farrer, Leach, Griffiths, Christensen, & Jorm, 2008; Jorm et al.,1997), or more daily concerns (e.g. in the areas of work, relation-ships, schooling) experienced by the younger age group in theirdaily life, increasing the likelihood of psychopathology. Also con-tradicting findings from epidemiological studies that have shownfemales to generally be at a higher risk of developing GAD (Carteret al., 2001; Hunt et al., 2002; Wittchen, 2002), female genderwas not a risk factor for more severe levels of generalized anxi-ety expressions. As the abovementioned factors are likely to havesimilar effects across gender, they could also explain the lack ofobserved gender differences. However, it could be a methodologicalartifact resulting from the response style of different groups.

A strong ethnicity effect was found in the current study, withIndians and individuals belonging to “Other” ethnicities experi-encing a higher risk for more severe levels of generalized anxietyexpressions. Similar ethnic differences were also found with regardto other mental disorder diagnoses, including MDD, alcohol abuse,and alcohol dependence (Chong et al., 2012). However, it is unclearif the differential effect was due to true differences in health status,or superficial differences in response style. Given that other factors,such as biological vulnerability and environmental factors, couldalso contribute to these ethnic differences (Chong et al., 2012),future studies clarifying the links between ethnicity and mentalhealth within the Singapore context are needed.

A high percentage of respondents with generalized anxietyexpressions had at least one other comorbid mental or physicalcondition, consistent with previous findings that GAD often co-occurs with other disorders (Judd et al., 1998; Kessler, Keller, &Wittchen, 2001; Starcevic, Portman, & Beck, 2012; Wittchen, 2002).For instance, somatic complaints and chronic pain issues, such asarthritis, migraine and back pain, have been found to be com-mon among individuals with GAD (Härter, Conway, & Merikangas,2003; Lieb et al., 2005; McWilliams, Cox, & Enns, 2003; McWilliams,Goodwin, & Cox, 2004). Unfortunately, the presence of comorbidchronic physical conditions hinders the likelihood of a correct diag-nosis of GAD (Ballenger et al., 2001), allowing many individualswith significant GAD symptoms to go undetected. Our findingssupport the screening and evaluation of individuals who show anx-iety symptoms for comorbid disorders, as early intervention can becritical in improving prognosis (Ballenger et al., 2001; Stein, 2000).

In the current sample, even the mildest form of generalizedanxiety expression was found to have a significant detrimentaleffect on daily functioning, suggesting that symptoms were onlyreported when they significantly impaired the individual’s daily life– pointing towards a high reporting threshold in current sample.Cultural differences in response style should be taken into accountwhen self-report measures are used to evaluate true health status(Jürges, 2007; Lindeboom & Van Doorslaer, 2004). The possibility ofhigh reference levels of reporting could explain the relatively lowprevalence of generalized anxiety expressions reported in the cur-rent sample. Additionally, individuals with subthreshold GAD andthreshold GAD were no less ‘ill’ than individuals who met full crite-ria for DSM-IV GAD. Our results suggest that both individuals whomeet full criteria for DSM-IV GAD as well as individuals with sub-threshold expressions of generalized anxiety experience seriousimpairment. Accordingly, all generalized anxiety expressions war-rant attention and treatment from medical professionals (Halleret al., 2014).

This study has its limitations. Exclusion of elderly respondentsliving in residential facilities might have contributed to an under-estimation of the prevalence of mental disorders among olderadults (Hobbs et al., 2014; Hunt et al., 2002). Second, the primary

xiety

mritas

5

sGlgitdmFssttmwemea

A

nRra

R

A

A

A

A

B

B

C

C

C

D

F

S.P. Lee et al. / Journal of An

easure used in the current study, the CIDI, was based on self-eport. As such, recall bias or perceived stigma might have led tonaccuracy in symptom reporting. Finally, the small proportion ofhe sample that met criteria for the various levels of generalizednxiety expressions might have resulted in insufficient power orkewness in statistical analyses.

. Conclusion

Using broader diagnoses than previous studies, the currenttudy examined the prevalence, correlates and comorbidity ofAD subthreshold expressions in Singapore’s multi-ethnic popu-

ation. We found that the prevalence of both DSM-IV GAD andeneralized anxiety expressions were lower than those observedn Western samples. However, our rates were comparable tohose found in other Asian countries, suggesting that culturalifferences in the manifestation and reporting of anxiety sympto-atology may influence the detection of GAD across countries.

urther research is needed to understand the specific effects ofuch differences. Despite the relatively low prevalence of GADubthreshold expressions, their substantial impact on daily func-ioning and associated high degree of comorbidity underscorehe importance of focusing clinical attention on individuals with

ilder forms of generalized anxiety expressions, not just on thoseho meet DSM-IV GAD criteria. Such preemptive intervention

fforts might be able to address concomitant complications stem-ing from comorbidity and improve daily functioning, ultimately

nhancing the well-being of individuals suffering from generalizednxiety.

cknowledgements

The study was supported by funding from the Singapore Millen-ium Foundation and the Ministry of Health, Singapore (grant no:F08-01). We would also like to thank Dr Hans-Ulrich Wittchen’sesearch team for providing the diagnostic algorithm of generalizednxiety expressions.

eferences

merican Psychiatric Association. (1994). Diagnostic and statistical manual of mentaldisorders (4th ed.). Washington, DC: American Psychiatric Association.

merican Psychiatric Association. (2013). Diagnostic and statistical manual of mentaldisorders: DSM-5. Washington, DC: American Psychiatric Association.

ngst, J., Gamma, A., Baldwin, D. S., Ajdacic-Gross, V., & Rössler, W. (2009). Thegeneralized anxiety spectrum: Prevalence, onset, course and outcome. EuropeanArchives of Psychiatry and Clinical Neuroscience, 259(1), 37–45.

snaani, A., Richey, J. A., Dimaite, R., Hinton, D. E., & Hofmann, S. G. (2010). A cross-ethnic comparison of lifetime prevalence rates of anxiety disorders. The Journalof Nervous and Mental Disease, 198(8), 551.

allenger, J. C., Davidson, J. R., Lecrubier, Y., Nutt, D. J., Borkovec, T. D., Rickels, K.,et al. (2001). Consensus statement on generalized anxiety disorder from theInternational Consensus Group on Depression and Anxiety. Journal of ClinicalPsychiatry, 62, 53–58.

eesdo-Baum, K., Winkel, S., Pine, D. S., Hoyer, J., Höfler, M., Lieb, R., et al.(2011). The diagnostic threshold of generalized anxiety disorder in the commu-nity: A developmental perspective. Journal of Psychiatric Research, 45(7), 962–972.

arter, R. M., Wittchen, H. U., Pfister, H., & Kessler, R. C. (2001). One-year preva-lence of subthreshold and threshold DSM-IV generalized anxiety disorder in anationally representative sample. Depression and Anxiety, 13(2), 78–88.

ho, M. J., Kim, J. K., Jeon, H. J., Suh, T., Chung, I. W., Hong, J. P., et al. (2007). Lifetimeand 12-month prevalence of DSM-IV psychiatric disorders among Korean adults.The Journal of Nervous and Mental Disease, 195(3), 203–210.

hong, S. A., Abdin, E., Vaingankar, J. A., Heng, D., Sherbourne, C., Yap, M., et al.(2012). A population-based survey of mental disorders in Singapore. Annals ofthe Academy of Medicine, Singapore, 41(2), 49.

epartment of Statistics, Ministry of Trade and Industry, Singapore. (2010, March).

Census of Population 2010 Statistical Release 1: Demographic Characteristics,Education, Language and Religion. Retrieved from: http://www.singstat.gov.sg/publications/publications-and-papers/cop2010/census10 stat release1

arrer, L., Leach, L., Griffiths, K. M., Christensen, H., & Jorm, A. F. (2008). Age differ-ences in mental health literacy. BMC Public Health, 8(1), 125.

Disorders 32 (2015) 73–80 79

Grant, B. F., Hasin, D. S., Stinson, F. S., Dawson, D. A., June Ruan, W., Goldstein, R.B., et al. (2005). Prevalence, correlates, co-morbidity, and comparative disabilityof DSM-IV generalized anxiety disorder in the USA: Results from the NationalEpidemiologic Survey on Alcohol and Related Conditions. Psychological Medicine,35(12), 1747–1759.

Guarnaccia, P. J. (1997). A cross-cultural perspective on anxiety disorders. CulturalIssues in the Treatment of Anxiety, 3–20.

Haller, H., Cramer, H., Lauche, R., Gass, F., & Dobos, G. J. (2014). The prevalence andburden of subthreshold generalized anxiety disorder: A systematic review. BMCPsychiatry, 14(1), 128.

Härter, M. C., Conway, K. P., & Merikangas, K. R. (2003). Associations between anx-iety disorders and physical illness. European Archives of Psychiatry and ClinicalNeuroscience, 253(6), 313–320.

Hobbs, M. J., Anderson, T. M., Slade, T., & Andrews, G. (2014). Relationshipbetween measurement invariance and age-related differences in the preva-lence of generalized anxiety disorder. Journal of Affective Disorders, 152, 306–312.

Hoge, E. A., Tamrakar, S. M., Christian, K. M., Mahara, N., Nepal, M. K., Pollack, M. H.,et al. (2006). Cross-cultural differences in somatic presentation in patients withgeneralized anxiety disorder. The Journal of Nervous and Mental Disease, 194(12),962–966.

Hunt, C., Issakidis, C., & Andrews, G. (2002). DSM-IV generalized anxiety disorder inthe Australian National Survey of Mental Health and Well-Being. PsychologicalMedicine, 32(4), 649–659.

Jorm, A. F., Korten, A. E., Jacomb, P. A., Christensen, H., Rodgers, B., & Pollitt, P. (1997).Mental health literacy: A survey of the public’s ability to recognise mental dis-orders and their beliefs about the effectiveness of treatment. Medical Journal ofAustralia, 166, 182–186.

Judd, L. L., Kessler, R. C., PauIus, M. P., Zeller, P. V., Wittchen, H. U., & Kunovac, J.L. (1998). Comorbidity as a fundamental feature of generalized anxiety dis-orders: Results from the National Comorbidity Study (NCS). Acta PsychiatricaScandinavica, 98(s393), 6–11.

Jürges, H. (2007). True health vs response styles: Exploring cross-country differencesin self-reported health. Health Economics, 16(2), 163–178.

Kessler, R. C., Berglund, P., Demler, O., Jin, R., Merikangas, K. R., & Walters, E. E. (2005).Lifetime prevalence and age-of-onset distributions of DSM-IV disorders in theNational Comorbidity Survey Replication. Archives of General Psychiatry, 62(6),593–602.

Kessler, R. C., Brandenburg, N., Lane, M., Roy-Byrne, P., Stang, P. D., Stein, D. J.,et al. (2005). Rethinking the duration requirement for generalized anxiety disor-der: Evidence from the National Comorbidity Survey Replication. PsychologicalMedicine, 35(07), 1073–1082.

Kessler, R. C., Keller, M. B., & Wittchen, H. U. (2001). The epidemiology of generalizedanxiety disorder. Psychiatric Clinics of North America, 24(1), 19–39.

Lalwani, A. K., Shavitt, S., & Johnson, T. (2006). What is the relation between culturalorientation and socially desirable responding? Journal of Personality and SocialPsychology, 90(1), 165.

Lee, S., Tsang, A., Chui, H., Kwok, K., & Cheung, E. (2007). A community epidemio-logical survey of generalized anxiety disorder in Hong Kong. Community MentalHealth Journal, 43(4), 305–319.

Lee, S., Tsang, A., Ruscio, A. M., Haro, J. M., Stein, D. J., Alonso, J., et al. (2009).Implications of modifying the duration requirement of generalized anxietydisorder in developed and developing countries. Psychological Medicine, 39(7),1163–1176.

Lee, S., Tsang, A., Zhang, M. Y., Huang, Y. Q., He, Y. L., Liu, Z. R., et al. (2007). Life-time prevalence and inter-cohort variation in DSM-IV disorders in metropolitanChina. Psychological Medicine, 37(1), 61–71.

Lewis-Fernández, R., Hinton, D. E., Laria, A. J., Patterson, E. H., Hofmann, S. G., Craske,M. G., et al. (2011). Culture and the anxiety disorders: Recommendations forDSM-V. Depression and Anxiety, 27(2), 212–229.

Liao, S. C., Chen, W. J., Lee, M. B., Lung, F. W., Lai, T. J., Liu, C. Y., et al. (2012). Low preva-lence of major depressive disorder in Taiwanese adults: Possible explanationsand implications. Psychological Medicine, 42(6), 1227–1237.

Lieb, R., Becker, E., & Altamura, C. (2005). The epidemiology of generalizedanxiety disorder in Europe. European Neuropsychopharmacology, 15(4), 445–452.

Lindeboom, M., & Van Doorslaer, E. (2004). Cut-point shift and index shift in self-reported health. Journal of Health Economics, 23(6), 1083–1099.

McWilliams, L. A., Cox, B. J., & Enns, M. W. (2003). Mood and anxiety disorders asso-ciated with chronic pain: An examination in a nationally representative sample.Pain, 106(1), 127–133.

McWilliams, L. A., Goodwin, R. D., & Cox, B. J. (2004). Depression and anxiety asso-ciated with three pain conditions: Results from a nationally representativesample. Pain, 111(1), 77–83.

Michael, T., Zetsche, U., & Margraf, J. (2007). Epidemiology of anxiety disorders.Psychiatry, 6(4), 136–142.

Oakley Browne, M. A., Wells, J. E., Scott, K. M., & Mcgee, M. A. (2006). Lifetimeprevalence and projected lifetime risk of DSM-IV disorders in Te Rau Hinengaro:The New Zealand mental health survey. Australian and New Zealand Journal ofPsychiatry, 40(10), 865–874.

Ruscio, A. M. (2002). Delimiting the boundaries of generalized anxiety disorder:

Differentiating high worriers with and without GAD. Journal of Anxiety Disorders,16(4), 377–400.

Starcevic, V., Portman, M. E., & Beck, A. T. (2012). Generalized anxiety disorder:Between neglect and an epidemic. The Journal of Nervous and Mental Disease,200(8), 664–667.

8 xiety

S

S

0 S.P. Lee et al. / Journal of An

tein, D. J. (2000). Comorbidity in generalized anxiety disorder: Impact and impli-cations. The Journal of Clinical Psychiatry, 62, 29–34.

ubramaniam, M., Vaingankar, J., Heng, D., Kwok, K. W., Lim, Y. W., Yap, M., et al.(2012). The Singapore Mental Health Study: An overview of the methodology.International Journal of Methods in Psychiatric Research, 21(2), 149–157.

Disorders 32 (2015) 73–80

Sue, D., & Sue, S. (1987). Cultural factors in the clinical assessment ofAsian Americans. Journal of Consulting and Clinical Psychology, 55(4),479.

Wittchen, H. U. (2002). Generalized anxiety disorder: Prevalence, burden, and costto society. Depression and Anxiety, 16(4), 162–171.