What is the evidence of variation in prevalence rates of generalized anxiety disorder across cultural groups?
Compared to 12-month community-based rates of DSM-IV-defined GAD in the United States, which range from 2.1 (
SE = 0.1) to 2.9% (
SE = 0.2), (
112,
113) lower 12-month rates are reported in several countries. These are 0.4% (
SE = 0.1) in Mexico, (
47) 0.8% (
SE = 0.3) in metropolitan China, (
12) 1.0% (
SE = 0.3) in South Korea, (
45) 1.2% (95% CI = 0.6–1.8) in Japan, (
46) and 1.4 (
SE = 0.2) in South Africa (
48). In Nigeria, no GAD cases were found over the previous 12 months, (
43) an uncharacteristically low prevalence even for this study, which reported low prevalence for all anxiety disorders. Rates similar to those in the United States are found in Australia (3.6%,
SE = 0.3) (
114) and in Europe, where the median prevalence in 27 studies is 1.7%, with an interquartile range of 0.8–2.2% (
7). A 1-month rate of 3.0% (95% CI = 2.1–3.9) was reported from Singapore, but this study used a two-stage assessment approach, including a clinician-administered diagnostic instrument (
115). In a large community-based study of 17 nations, mean 12-month rates of GAD are twice as high in developed countries (1.7%,
SE = 0.1) as in developing countries (0.8%,
SE = 0.1) (
6). Lifetime community prevalence of GAD shows similar cross-national variation (
6).
Other studies have focused on comparisons of diverse cultural and ethnic groups within one country. In the United States, lifetime risk for DSM-IV-defined GAD is higher for non-Latino Whites than for Asian Americans, African Americans, Caribbean Blacks, and Latinos (
50,
51,
113). This confirms similar findings of ethnic variation using DSM-III- and DSM-III-R criteria. The ECA study found that lifetime rates of DSM-III-defined GAD varied by ethnicity and nativity: non-Latino Whites reported twice the prevalence of GAD than US-born Mexican Americans and over four times the prevalence reported by Mexican immigrants (6.9% [
SE = 0.9] versus 3.4% [
SE = 0.8] versus 1.6% [
SE = 0.5], respectively) (
5). Using DSM-III-R criteria, not a single case of GAD was found among 3,012 persons of Mexican descent in a California community study using the CIDI, despite a lifetime prevalence of 16.8% (
SE = 0.1) for any anxiety disorder (
116). This was attributed by the authors to participants' inability to understand key instrument items. Research in other countries has also shown substantial interethnic variability. A study of Mapuche Indians in Chile (
49) found significantly lower rates of 12-month DSM-III-R-defined GAD among the Mapuche (0.1%, 95% CI = 0.0–0.3) than in the non-Mapuche local population (1.9%, 95% CI = 0.7–3.1). And in Singapore, the lifetime rate of GAD is significantly higher among the ethnic Chinese than the Malay (3.5% [95% CI = 2.3–4.7] versus 2.2% [95% CI = 1.3–3.2]), after adjusting for demographic characteristics (
115).
The causes of these cross-racial/ethnic differences in prevalence remain unclear. Non-Western samples (i.e., Asian, African, indigenous) tend to show much lower rates of GAD than individuals of European descent, and this pattern is reproduced in an attenuated form among racial/ethnic minorities in the United States (especially among less acculturated subgroups). One possibility is that application of DSM-IV GAD criteria result in spuriously lower rates in settings of higher socioeconomic deprivation, possibly because the excessiveness criterion is not endorsed. However, true differences in prevalence and measurement discrepancies cannot be ruled out (
117). Item-level analysis of the probability of endorsement across cultural groups and clinical reappraisal studies that include ethnographic assessment of local expressions of anxiety are needed to resolve this issue.
What is the cross-cultural validity of existing generalized anxiety disorder diagnostic criteria?
Assessing worry: Prolonged, excessive worry is the hallmark of GAD in DSM-IV-TR. Although worry is a universal phenomenon, research on the cross-cultural validity of instruments assessing worry is limited and has produced mixed results. Some studies find similar response patterns cross-nationally on translated scales of pathological worry among patients with GAD (
118,
119). Others find cross-racial/ethnic differences in scale endorsement, such as higher worry scores on three psychometrically validated anxiety scales among Mexican youth in Mexico and Hispanic youth in the United States than among Euro-Americans (
120). Finally, some researchers find equivalent scores across racial/ethnic groups on some scales but not others in the same study; for instance, on the Penn State Worry Questionnaire (PSWQ) versus the Worry Domains Questionnaire (WDQ) among college students (
121). However, most of this research has been conducted in normal samples and data are lacking on how to translate these findings to GAD populations.
Apprehensive expectation: Halbreich and colleagues (
122) asked psychiatrists from Western and non-Western countries to describe their patients' experience of various types of dysphoria, including apprehensive expectation. Although clinicians from very different countries (i.e., India, Peru, and Morocco) describe similar experiences of worry, there are also differences in the particular expressions they used. These range from expectations of danger (e.g., “something bad is going to happen to me or my family,” “expecting the worst”), to frank fear (e.g., “feel myself afraid”), to more embodied/somatic experiences (e.g., “something that does not give me rest”). We found no research studies that systematically evaluated the cross-cultural validity of apprehensive expectation as the hallmark of GAD, and therefore, cannot assess the diagnostic accuracy of this aspect of Criterion A.
Excessiveness criterion: Cross-cultural data on the diagnostic validity of this criterion is limited. GAD cases in the United States defined with or without the excessiveness criterion do not differ in race/ethnicity distribution or other demographic characteristics; both criterial definitions are less likely to be met by Hispanics and African Americans than non-Hispanic Whites (
123). In the NCS-R, removing the excessiveness criterion increased prevalence of GAD by 40% (
123). In Hong Kong, a community assessment that obtained prevalence rates without the excessiveness criterion resulted in a 6-month GAD prevalence of 4.1%, (
124) many times higher and much closer to US rates than the 0.8% 12-month rate found in Beijing and Shanghai using full DSM-IV criteria (
12). However, the methodological differences across the studies and the indirect nature of the evidence perhaps raise more questions than they answer. In the absence of additional data, no specific changes are proposed to the excessiveness criterion.
Duration requirement: The validity of the 6-month duration criterion for GAD has been questioned, because shortening the required duration has little impact on several characteristics of the disorder, such as functional impairment, comorbidity, clinical course, and heritability (
6,
112). The cross-cultural implications of loosening the 6-month requirement was recently investigated, using representative community data from 7 developing and 10 developed nations (
N = 85,052) (
6). Findings reveal that varying the duration criterion to 1 month, 3 months, or 12 months has proportionally equivalent effects in onset, course, impairment, comorbidity, and recovery rate across developing and developed countries. Similarly, in the United States, NCS-R data shows no racial/ethnic variation across different disorder durations (
112). In summary, based on the limited available literature, there are no data to suggest that shortening the duration criterion will have a differential effect across racial/ethnic groups.
Number and content of worry domains: Cross-national research on the number of worry domains endorsed by respondents with GAD compared to those with subthreshold or no GAD is limited, and generally supports the view that cases meeting full criteria report more worry domains (
124). In terms of the content of worry domains, there is limited evidence of cross-cultural variability. A study of US college students showed significantly lower scores among African Americans than Caucasians or Asian Americans, in several worry content areas of the WDQ other than finances (relationship stability, self-confidence, future aims, and work competence), despite similar levels of pathological worry on the PSWQ (
121). Asian Americans, by contrast, scored significantly higher than the other groups on the “aimless future” domain, a measure of worry about unfulfilled expectations. The authors suggested that cross-ethnic similarities in PSWQ scores indicate equivalent total level of worry across racial/ethnic groups, but that African Americans focus on content areas not tapped by the WDQ. This study focused on the general college student population, rather than on individuals with GAD, raising questions about its applicability to GAD criteria. Hong Kong respondents with GAD worry about similar domains as Western samples (e.g., finances, family, health) (
124). However, some worry domains are culturally specific, such as the concern of Cambodian refugees with GAD over the spiritual status of deceased relatives (
40). The racial/ethnic distribution of the number, intensity, and content of worry domains should be evaluated further in order to provide valid examples in the GAD criteria and text.
Difficult-to-control worry: Criterion B specifies that pathological worry that meets criteria for GAD is “difficult to control.” Very limited data is available on the cross-cultural validity of this criterion. One study found low rates of GAD in a Peruvian nonclinical sample as a result of nonendorsement of this criterion when assessed with the Spanish equivalent of the word “uncontrollable” (
125). Respondents' PSWQ responses, however, frequently indicated difficulty controlling worry (e.g., “once I start worrying I cannot stop”), suggesting lack of semantic equivalence in instrument translation, rather than symptom variability, in explaining the observed difference in prevalence.
Associated symptoms: The most robust data for cross-cultural variability in GAD expression involves the types of symptoms associated with the disorder. Several studies have found that individuals from non-Western societies are very likely to endorse somatic symptoms as a key aspect of pathological worry. This research was conducted in cultures as distinct as Nepal, Mexico, the United Arab Emirates, and Hong Kong. GAD patients from urban mental health care facilities in Nepal, for example, scored higher than US GAD patients on the somatic subscale of the Beck Anxiety Inventory (BAI), despite similar overall BAI scores; the more commonly endorsed somatic symptoms are dizziness and indigestion (
126). In contrast, the US group scores higher on the psychological subscale measuring feeling “scared” and “nervous.” In a cross-national comparison, Mexican youths in Mexico reported more anxiety-related somatic symptoms than Euro-American youths (
120). A study that explored “psychological” versus “somatic” presentations of psychiatric disorders among primary care patients in the United Arab Emirates found that patients who meet criteria for GAD are more likely, on the basis of symptom profiles and attributions, to have predominantly somatic presentations (18.8%) than psychological ones (14.3%) (
127). In a Hong Kong community sample, (
124) respondents who met full GAD criteria were significantly more likely than subthreshold cases (defined as those who did not meet criterion C) to endorse associated somatic symptoms that are not included in the DSM-IV criteria, such as palpitations (52 versus 34%), difficulty breathing (38 versus 22%), and sweating (33 versus 22%). However, full GAD cases are also significantly more likely to report DSM-IV symptoms, such as fatigue (84 versus 74%), irritability (81 versus 65%), difficulty concentrating (83 versus 67%), sleep disturbance (76 versus 51%), and muscle tension (74 versus 55.5%).
Differences in reports of somatic versus psychological symptoms associated with GAD have even been found in the same individuals, depending on the language used to report their symptoms. For example, a convenience sample (
n = 87) of bilingual US Latinos with GAD completed several anxiety scales, including the BAI and PSWQ, in both the English original and Spanish translation (
128). Subjects' Spanish-language responses across all scales combined yielded two factors, characterized as somatic and psychological,which accounted for 59% and 17% of the variance, respectively. By contrast, the English-language responses of the same participants yielded a single factor, accounting for 64% of the variance. Moreover, the PSWQ, a measure of psychological worry, predicted ADIS-IV-defined GAD severity only for the English-speaking assessment, whereas the Beck Anxiety Inventory, which measures primarily physiological symptoms of anxiety, predicted GAD severity for both language cohorts. This contrasts with previous research, which found a lower association between GAD severity and autonomic arousal symptoms in Caucasian patients (
129). The finding that bilingual Latinos tend to use somatic expressions to describe their GAD symptoms in Spanish and psychological ones to describe the same condition in English suggests that Spanish-monolingual Latinos with GAD may be less likely to be identified, if largely psychological criteria are adopted for the disorder.
The prevalence of somatic symptoms of GAD cross-culturally raises questions about the primacy ascribed in DSM-IV to the psychological components of generalized anxiety. This classification may be less valid for cultures where somatic presentations of generalized anxiety appear to be more common than cognitive psychological ones, or at least more prominent on initial evaluation (
130). The inclusion of a fuller array of somatic symptoms appears to be particularly important in light of the finding that patients with somatic anxiety display higher levels of distress, disability, and use of medical services compared to patients with primarily psychological manifestations (
131).
Although the current DSM-IV-TR GAD criteria include several somatic symptoms (i.e., fatigue, muscle tension, sleep disturbance), many that have been reported among GAD sufferers in studies with non-US samples are missing (i.e., palpitations, bowel symptoms, dizziness, indigestion). These hyperarousal symptoms were included in the DSM-III-R GAD criteria and remain in ICD-10, but were removed for DSM-IV, in order to increase the discriminant validity of GAD against nonanxious controls (
132). However, this may have inadvertently resulted in reduced cross-cultural validity of the criteria.
Impairment: There is very limited cross-cultural data on differential impairment associated with meeting GAD criteria. Among US community respondents with GAD, non-Latino Whites have significantly lower 30-day functional impairment than African Americans (
51). Respondents with GAD in developing countries endorse less impairment on the Sheehan Disability Scale, despite reporting a similar number of out-of-role days as their counterparts in developed countries (
6). Unlike the more objective measure of out-of-role days, it is possible there were cross-cultural differences in interpreting and responding to SDS items; however, true differences in impairment cannot be ruled out.