The cross-national epidemiology of social anxiety disorder: Data from the World Mental Health Survey Initiative

Background There is evidence that social anxiety disorder (SAD) is a prevalent and disabling disorder. However, most of the available data on the epidemiology of this condition originate from high income countries in the West. The World Mental Health (WMH) Survey Initiative provides an opportunity to investigate the prevalence, course, impairment, socio-demographic correlates, comorbidity, and treatment of this condition across a range of high, middle, and low income countries in different geographic regions of the world, and to address the question of whether differences in SAD merely reflect differences in threshold for diagnosis. Methods Data from 28 community surveys in the WMH Survey Initiative, with 142,405 respondents, were analyzed. We assessed the 30-day, 12-month, and lifetime prevalence of SAD, age of onset, and severity of role impairment associated with SAD, across countries. In addition, we investigated socio-demographic correlates of SAD, comorbidity of SAD with other mental disorders, and treatment of SAD in the combined sample. Cross-tabulations were used to calculate prevalence, impairment, comorbidity, and treatment. Survival analysis was used to estimate age of onset, and logistic regression and survival analyses were used to examine socio-demographic correlates. Results SAD 30-day, 12-month, and lifetime prevalence estimates are 1.3, 2.4, and 4.0% across all countries. SAD prevalence rates are lowest in low/lower-middle income countries and in the African and Eastern Mediterranean regions, and highest in high income countries and in the Americas and the Western Pacific regions. Age of onset is early across the globe, and persistence is highest in upper-middle income countries, Africa, and the Eastern Mediterranean. There are some differences in domains of severe role impairment by country income level and geographic region, but there are no significant differences across different income level and geographic region in the proportion of respondents with any severe role impairment. Also, across countries SAD is associated with specific socio-demographic features (younger age, female gender, unmarried status, lower education, and lower income) and with similar patterns of comorbidity. Treatment rates for those with any impairment are lowest in low/lower-middle income countries and highest in high income countries. Conclusions While differences in SAD prevalence across countries are apparent, we found a number of consistent patterns across the globe, including early age of onset, persistence, impairment in multiple domains, as well as characteristic socio-demographic correlates and associated psychiatric comorbidities. In addition, while there are some differences in the patterns of impairment associated with SAD across the globe, key similarities suggest that the threshold for diagnosis is similar regardless of country income levels or geographic location. Taken together, these cross-national data emphasize the international clinical and public health significance of SAD.


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Conclusions: While differences in SAD prevalence across countries are apparent, we found a number of consistent patterns across the globe, including early age of onset, persistence, impairment in multiple domains, as well as characteristic sociodemographic correlates and associated psychiatric comorbidities. In addition, while there are some differences in the patterns of impairment associated with SAD across the globe, key similarities suggest that the threshold for diagnosis is similar regardless of country income levels or geographic location. Taken together, these cross-national data emphasize the international clinical and public health significance of SAD.
Keywords: Social anxiety disorder, Social phobia, Cross-national epidemiology, World Mental Health Survey Initiative Background There is evidence from both community and clinical studies that social anxiety disorder (SAD), previously termed social phobia, is a prevalent and disabling disorder. In the National Comorbidity Survey (NCS) and National Comorbidity Survey Replication (NCS-R), SAD was one of the most common of all mental disorders (with lifetime prevalence estimates of 16% and 12.1% respectively) [1,2]. In each of these surveys, SAD age of onset was early, comorbidity with other mental disorders was high, and subsequent impairment was notable [3,4]. Research in clinical settings has also indicated that SAD is a prevalent and disabling condition in this context [5,6]. Such data have been key in suggesting the clinical and public health relevance of SAD.
Nevertheless, most of the available data on the epidemiology of SAD originate from high income countries in the West. European epidemiological data have largely been consistent with US data, emphasizing the high prevalence, comorbidity, and morbidity of SAD [7]. A study using the Diagnostic Interview Schedule in four countries (USA, Canada, Korea, and Puerto Rico) found some consistent patterns, including higher rates in females and considerable comorbidity [8]. Still, many questions about the crossnational epidemiology of SAD remain unanswered. It has been suggested, for example, that anxiety disorders such as SAD are a peculiarly Western construct (in the East, for example, there may be more concern with offending others than with embarrassing oneself) [9]; from this perspective it might be hypothesized that SAD is less prevalent elsewhere, or that thresholds for SAD diagnosis differ across the globe.
Few data have systematically addressed the 30-day prevalence of SAD (which is important in establishing the prevalence at a particular point in time), whether age of onset and persistence vary across a range of different countries, whether impairment associated with SAD differs from place to place, and whether SAD treatment differs across the globe. Data on socio-demographic correlates of SAD and on comorbidity with other mental disorders have again mainly been reported in high income Western contexts. The WHO World Mental Health (WMH) Survey Initiative provides an important opportunity to investigate the epidemiology of SAD across a range of countries. In the current study, we assessed 30-day, 12-month, and lifetime SAD prevalence; age of onset; persistence; severity of role impairment associated with SAD; and treatment of SAD, across countries. In addition we investigated sociodemographic correlates of SAD, and comorbidity of SAD with other mental disorders, in the combined sample.
All but ten surveys were based on area probability household samples representative of the entire nation (see Table 1 for survey details). The exceptions were surveys of all urbanized areas in three countries (Colombia, Mexico, Peru), of a specific region in two countries (Colombia-Medellin, Spain-Murcia), of specific metropolitan areas in three countries (São Paulo in Brazil; a series of cities in Japan; Beijing, Shanghai and Shen Zhen in PRC) and of selected states in one country (Nigeria). Respondents had to be at least 18 years of age in most countries (20 in Japan). Five surveys (Colombia, Colombia-Medellin, Mexico, Peru, Poland) had an upper age limit (64 or 65), and one (Australia) had an upper age limit of 85.
Interviews were conducted face to face in respondent homes after obtaining informed consent. Human Subjects Committees monitored the surveys and approved recruitment and consent procedures in each country. Other than in Australia, Iraq, Romania, and South Africa, where all  respondents were administered the full interview, internal subsampling was used to reduce respondent burden by dividing the interview into two parts. Part 1 assessed core disorders, including SAD, and was administered to all respondents. Part 2 included additional disorders and correlates and was administered to all Part 1 respondents who met criteria for any lifetime Part 1 disorder plus a probability subsample of other respondents. Part 1 data were weighted to adjust for differential probabilities of selection and to match population distributions on census sociodemographic and geographic distributions. Part 2 data were additionally weighted for the under-sampling of Part 1 respondents without core disorders. Response rates range from a low of 45.9% (France) to 97.2% (Colombia-Medellin) (69.4% weighted average) ( Table 1). Technical details about WMH sample design are presented elsewhere [11].

Measures
The WMH interviews assess prevalence and a wide range of predictors and consequences of numerous anxiety, mood, impulse control, and substance use disorders [12]. The full text of the interview schedule is available at www.hcp.med.harvard.edu/wmh. The WMH interview schedule was developed in English and translated into other languages using a standardized WHO translation, back-translation, and harmonization protocol described elsewhere [13]. Consistent interviewer training and quality control monitoring procedures were used in all surveys to facilitate crossnational comparison [14]. The following sections emphasize the measures considered in the current report.

Mental disorders
SAD and other Diagnostic and Statistical Manual of Mental Disorders (DSM)-IV anxiety (i.e., panic disorder with or without agoraphobia, agoraphobia without panic disorder, generalized anxiety disorder, specific phobia, post traumatic stress disorder, and separation anxiety disorder), mood (i.e., major depressive episode, bipolar disorder), impulse control (i.e., intermittent explosive disorder, bulimia nervosa, binge eating disorder, oppositional defiant disorder, conduct disorder, attention deficit disorder), and substance use disorders (i.e., alcohol abuse and drug abuse with or without dependence) were assessed using Version 3.0 of the WHO Composite International Diagnostic Interview (CIDI 3.0) [15], a fully structured lay-administered interview. Respondents were administered the full SAD section if they endorsed a diagnostic stem question for one or more performance or interactional fears described as excessive and causing substantial distress or avoidance. The SAD section screened for lifetime experiences of shyness, fear, and discomfort associated with each of 14 social situations. Respondents endorsing one or more such questions were asked about all DSM-IV criteria. Age of onset (AOO) of each disorder was assessed using special probing techniques shown experimentally to improve recall accuracy [16]. CIDI diagnoses were compared to blinded clinical diagnoses using the Structured Clinical Interview for DSM-IV (SCID) [17] in probability subsamples of WMH respondents from France, Italy, Spain, and the USA. As detailed elsewhere, good CIDI-SCID diagnostic concordance was found for SADarea under the curve (AUC) = 0.67and most other DSM-IV/CIDI disorders [18].

Impairment
The Sheehan Disability Scale (SDS) [19] was used to assess recent impairment in role functioning in each of four domains (home, work, relationship, and social) in respondents with a 12-month SAD diagnosis. The response scale is from 0 to 10, with severe impairment in a specific role domain defined as a score ≥7. In addition, respondents were asked how many days in the past year they were unable to work or carry out their normal activities due to their disorder (days out of role).

Treatment
The 12-month treatment was assessed by asking respondents if they had seen any of a list of professionals for problems with emotions, nerves, mental health, or alcohol or drug use, including both inpatient and outpatient care. Sectors included were as follows: specialty mental health  The projected risk for this country is at age 64 because the age range of this survey is between 18-64 SE standard error (e.g., psychiatrist and non-psychiatrist mental health specialist), general medical (e.g., general practitioner), human services sector (e.g., religious advisor), and complementary and alternative medicine (e.g., herbalist or homeopath).

Statistical analysis
Cross-tabulations were used to calculate prevalence, impairment, comorbidity, and treatment. Significance was calculated using Wald and McNemar's chi-square tests. Survival analysis was used to estimate AOO and projected lifetime risk, as the young age of many respondents biases the AOO distribution downwards. The actuarial method implemented in SAS 9.4 (PROC LIFETEST) was used to generate the AOO curves. Logistic regression and survival analyses were used to examine socio-demographic correlates. Because the data were weighted and clustered, the Taylor series linearization method [21] implemented in the SUDAAN software package 11.0 [22] was used to estimate design-based standard errors. Statistical significance was consistently evaluated using two-sided tests, with P < 0.05 considered significant.

Prevalence
On average, the estimated lifetime, 12-month, and 30-day prevalence is highest in high income countries (5.5%, 3.1%, 1.7%), intermediate in upper-middle income countries (2.9%, 2.1%, 1.3%), and lowest in low/lower-middle income countries (1.6%, 1.0%, 0.5%) ( Table 2). Prevalence rates are highest in the Americas and the Western Pacific region, and lowest in Africa and the Eastern Mediterranean. Across all countries, SAD is a prevalent disorder (4.0%, 2.4%, 1.3%). Comparison of lifetime, 12-month, and 30-day prevalence across all countries, across different income groups, and across different regional groups all reached significance (P < 0.001) ( Table 2). The ratio of the 12-month prevalence to lifetime prevalence is an indirect indicator of disorder persistence. This ratio is lowest in high income countries (57.3%) and the   Table 2). Table 3 and Fig. 1 indicate that the median estimated AOO is similar for high income, upper-middle income, and low/lower-middle income countries. Across all countries, the risk period for onset of SAD ranges from the mid-late adolescence to the early 40s. In high income countries, the earliest median AOO estimates occurr in Poland (50% by age 11), whereas the latest are in The Netherlands (50% by age 17). In upper-middle countries, the earliest median AOO estimates are in Colombia (50% by age 13), and the latest in South Africa (50% by age 26). In low/lower-middle income countries, the earliest median AOO estimates are in Nigeria (50% by age 11), and the latest in Peru (50% by age 16). Projected lifetime risk for SAD across the globe is 4.4%.

Impairment
SAD is associated with substantial impairment in multiple domains of role functioning in the WMH data (Table 4) and with a mean number of days out of work of 24.7 (1.8) in the past year (Appendix 1: Table 8). However, in most countries, the proportion of respondents with 12-month SAD and severe role impairment (SDS score of 7-10) is higher in the domains of relationships and social situations than in the domains of home and work. Furthermore, in most countries, between one-third and one-half of respondents with 12-month SAD have severe role impairment in at least one domain. Notably, there are no significant differences between low, middle, and high income groups, or between different WHO regions, in the proportion of respondents with severe role impairment in at least one domain. However, there are significant differences across countries in proportion of 12-month SAD respondents with severe role impairment in any of the domains (ranging from 9.4% in PRC Shen Zhen to 71.6% in Spain-Murcia) ( Table 4), and there are also some differences in specific domains across country, income region, and WHO region. The proportion of respondents with severe home impairment varies significantly by country and by WHO region; it is lowest in PRC Shen Zhen (2.1%) and the Western Pacific (8.1%), and highest in The Netherlands (41.9%) and the Eastern Mediterranean (15.8%). The proportion of respondents with severe work impairment varies significantly by country and by WHO region; it is lowest in the PRC Shen Zhen (1.4%) and the Eastern Mediterranean (8.4%), and highest in the Netherlands (56.8%) and Western Europe (20.2%). The proportion of respondents with severe relationship impairment varies significantly by country and by income region (lowest in low/lower-middle income countries, i.e., 18%, and highest in uppermiddle income countries, i.e., 28.5%). The proportion of respondents with severe social impairment varies by country, by WHO region (lowest in Eastern Europe, i.e., 17.6%, highest in Western Europe, i.e., 31.4%), and by income region (lowest in low/lower-middle income, i.e., 21.2%, highest in high income, i.e., 29.8%). Table 5 shows the bivariate associations of the sociodemographic characteristics with SAD in the combined sample. Both 30-day and lifetime risk of SAD are associated with younger AOO, female gender, not being employed, being unmarried (never married or divorced/widowed/separated), lower educational status, and low household income. SAD recurrence (as indicated by 12-month SAD in lifetime cases) is associated with female gender, earlier AOO, and being unmarriedwhile persistence (as indicated by 30-day SAD in 12-month cases) is associated with  Chi-square test of homogeneity to determine if there is variation in impairment severity across countries. McNemar's chi-square test to determine if there is a significant difference for c home vs work impairment, d home vs relationship impairment, e home vs social impairment, f work vs relationship impairment, g work vs social impairment, h relationship vs social impairment for each row entry. For example, c for Colombia indicates that the proportion with severe impairment associated with social anxiety disorder is significantly higher for work than home , and both recurrence and persistence are associated with being a homemaker. Socio-demographic correlates are similar across countries for the most part, but also demonstrate some differences (Appendix 2: Table 9, Appendix 3: Table 10, and Appendix 4: Table 11).

Treatment
Among those with 12-month SAD, the percentage reporting treatment of any kind (i.e., specialty mental health, general medical care, health care, human services, complementary and alternative medicine, non-health care) in the past   Respondents with any disorder listed above f Percentage of respondents with either lifetime or 12-month SAD who also meet lifetime criteria for at least one of the other DSM-IV disorders g The human services sector or complementary and alternative medicine (CAM) sector h Percentage of respondents with either lifetime or 12-month SAD and at least one of the other disorders, whose age of onset of SAD is reported to be younger than the age of onset of all comorbid disorders under consideration (i.e., either mood, anxiety, substance use, impulse control, or any disorder) SE standard error  12 months differs significantly by impairment, with 38% receiving any treatment (Table 7). Across all countries, any treatment is lowest in those with moderate impairment (27.4%), and highest in those with severe impairment (46.9%). This pattern holds true for specialty mental health, general medical care, and health care, but human services, complementary and alternative medicine, and non-health care are most commonly used by those with mild impairment. Treatment rates for those with any impairment are lowest in low/lower-income countries (18.0%), and highest in high income countries (44.2%). This pattern holds true for cases with any impairment across all treatment sectors, and for almost all treatment sectors across different levels of impairment.

Discussion
A number of limitations of the current study deserve mention. A first important issue is that of sampling. Response rates differ widely across the WMH surveys [12]; while response rates do not appear to be related to SAD prevalence, it is possible that in some settings, particularly those where treatment is less available, those with the most severe SAD were unable to participate in surveys. Surveys also differed in their focus; some included only metropolitan areas, while others employed nationally representative samples; such differences may also have affected prevalence estimates. The surveys also excluded a range of respondents, including institutionalized patients, and people who were too intoxicated to be interviewed. Finally, samples in the WMH surveys also reflected survivor bias; given the 10-to 15-year gap in life expectancy between those in lower and higher income countries, this may also affect prevalence estimates [23]. Taken together, the prevalence rates provided here are therefore conservative. It is also relevant to note that only two African countries were studied, limiting conclusions about distinctions across geographic regions. Second, the measure of SAD used in the WMH surveys has important limitations. The CIDI relies on a screening section that employs relatively few stem questions, and this may lead to under-estimation of SAD in some settings (as noted, there is no stem question that addresses the symptom of offending others, which is thought to characterize social anxiety in some cultures, and which is now captured in the DSM-5 diagnostic criteria for SAD) [24][25][26][27]. Furthermore, no attempt was made to develop distinct cut-off points for SAD in different countries or to go beyond the DSM-IV criteria to develop distinct criteria for different countries that might have increased detection of SAD. It is relevant to emphasize that in countries where blinded clinical reappraisal interviews were undertaken, there was no evidence for systematic bias in the diagnostic threshold for SAD [18]. However, clinical reappraisal interviews were carried out in only a subset of WMH countries, and it is possible that such studies would have found systematic differences in CIDI sensitivity and specificity across contexts.
Bearing in mind these limitations, the WMH surveys provide unique cross-national data on SAD, and are able to address a number of questions about this disorder. Some Table 7 Among those with 12-month SAD, percent reporting treatment in the past 12 months by Sheehan impairment severity (Continued)  The mental health specialist sector or the general medical sector f The human services sector (religious or spiritual advisor or social worker or counselor in any setting other than a specialty mental health setting) g The CAM (complementary and alternative medicine) sector (any other type of healer such as herbalist or homeopath, participation in an Internet support group, or participation in a self-help group) h The human services sector or CAM i Respondents who sought any form of professional treatments listed in the footnotes above cross-national differences in SAD epidemiology are apparent: SAD 30-day, 12-month, and lifetime prevalence are lowest in low/lower-middle income countries and in the African and Eastern Mediterranean regions, highest in upper-middle income countries and the Americas and the Western Pacific regions, and there are some differences in domains of role impairment and in treatment rates across country, income region, and WHO region. Crucially, however, there are a number of consistent patterns across the globe: SAD has an early age of onset, is a persistent disorder, and is associated with specific socio-demographic features (younger age, female sex, unmarried status, lower education, and lower income) and with similar patterns of comorbidity and health care utilization.
A previous cross-national study indicated that SAD prevalence differs across different countries, with lifetime prevalence estimates ranging from 0.5 in Korea to 2.6 in the USA [8]. However, that survey was done in only four countries, and assessed only three social fears as part of the simple phobia section of the Diagnostic Interview Schedule. The current data extend such work with surveys across a broad range of countries, and with a comprehensive assessment of SAD. Differences in prevalence across countries continue to be observed, as is the case for other common mental disorders in the WMH surveys. Such differences may reflect artifactual variation across surveys (for example, mental disorder stigma may be higher in lower income settings, resulting in decreased willingness to self-disclose, and an underestimation of prevalence) or cross-national differences in underlying mechanisms relevant to pathogenesis (for example, greater access to greater social capital and more community engagement in lower income countries).
However, the finding here of similar proportions of SAD respondents with any severe role impairment across country income and geographic groupings suggests that differences in prevalence are not simply due to regional differences in diagnostic thresholding. In higher income countries and in particular regions of the globe such as the Americas, Western Pacific, and Western Europe, there is a higher prevalence of SAD, and SAD is associated with more impairment in the social domain than in other domains, suggesting high demands for social performance in such contexts. The persistence of SAD as well as proportion with any role impairment are highest in upper-middle income countries, Africa, and the Eastern Mediterranean, perhaps pointing to growing performance demands in these regions, but with fewer treatment resources than in higher income countries. The disjunction between lower prevalence but higher persistence of SAD in particular regions may be valuable in suggesting hypotheses, such as this one, about relevant causal mechanisms in SAD.
Our findings that SAD epidemiology demonstrates similar patterns across the globe, being associated with early age of onset, impairment in multiple domains, characteristic socio-demographic correlates (younger age, female gender, unmarried status, lower education, lower household income), and particular patterns of mental disorder comorbidity, again confirms and extends previous work. Thus, for example, we were able to demonstrate that across the globe SAD disorder persistence is particularly highly associated with lower education, episode persistence is particularly associated with being a student, while both disorder and episode persistence are associated with being a homemaker. While it has previously been demonstrated that SAD more likely follows other anxiety disorders, and precedes depression [1], here we provide novel data on the comorbidity of SAD with impulse control disorders; this is valuable given that a link between social anxiety and aggression has been posited in the animal and clinical literature [28,29]. It is notable that in both lifetime and 12-month SAD, SAD begins earlier in only 31.4-35.4% of cases of comorbid anxiety disorder, due to the common comorbidity with specific phobia which has the earliest onset of the anxiety disorders, but SAD begins earlier in 48.8-80.9% of cases of comorbid mood disorder, substance use disorder, or impulse control disorder. We also provide novel data on treatment rates; these are highest where impairment is most severe and in countries with higher income.

Conclusions
In conclusion, data from the WMH survey provide the most comprehensive picture of the global epidemiology of SAD to date and help address the key question of whether this condition is a peculiarly Western construct. There are apparent differences in SAD prevalence and domains of role impairment across the globe, with further work needed to delineate more rigorously the reasons for such differences and to investigate possible mechanisms relevant to understanding them. Nevertheless, the data indicate that across the world, SAD is a prevalent condition that is characterized by early age of onset, as well as disorder and episode persistence. Furthermore in low, middle, and high income countries, as well as in a range of geographic regions, SAD is associated with specific socio-demographic correlates (younger age, female gender, unmarried status, lower education, lower household income), particular comorbidity patterns (typically beginning later than specific phobia, but earlier than other anxiety disorders, mood, substance use, or impulse control disorders), and common patterns of health care utilization. Taken together, these cross-national data emphasize the international clinical and public health significance of SAD.       Education level difference d χ 2 3 = 12.9*, P = 0.044 χ 2 3 = 10.6, P = 0.102 χ 2 3 = 37.1*, P < 0.001 χ 2 3 = 9.3, P = 0.157