When prevalence estimates were based on the examination of psychiatric clinic samples, social anxiety disorder was thought to be a relatively rare disorder. The opposite was instead true; social anxiety was common but many were afraid to seek psychiatric help, leading to an understatement of the problem. Prevalence rates vary widely because of its vague diagnostic criteria and its overlapping symptoms with other disorders. There has been some debate on how the studies are conducted and whether the illness truly impairs the respondents as laid out in the official criteria. Psychologist Dr. Ray Crozier argues, "it is difficult to ascertain whether the person being interviewed adheres to the DSM-III-R criteria or whether they are merely exhibiting poor social skills or shyness."

The National Comorbidity Survey of over 8,000 American correspondents in 1994 revealed a 12-month and lifetime prevalence rates of 7.9% and 13.3% making it the third most prevalent psychiatric disorder after depression and alcohol dependence and the most apparent of the anxiety disorders. According to U.S. epidemiological data from the National Institute of Mental Health, social phobia affects 5.3 million adult Americans in any given year. Recent studies suggest the lifetime prevalence number may be as high as 15 million people or 6.8% of the American population. Cross-cultural studies have reached prevalence rates with the conservative rates at 5% of the population. However, other estimates vary within 2% and 7% of the U.S. adult population.

Onset of social phobia typically occurs between 11 and 19 years of age. Onset after age 25 is rare. Social anxiety disorder occurs in females twice as often as males, although men are more likely to seek help. The prevalence of social phobia appears to be increasing among white, married, and well-educated individuals. As a group, those with generalized social phobia are less likely to graduate from high school and are more likely to rely on government financial assistance or have poverty-level salaries. Surveys carried out in 2002 show the youth of England, Scotland, and Wales have a prevalence rate of .4%, 1.8%, and .6%, respectively. The prevalence of self-reported social anxiety for Nova Scotians older than 14 years was 4.2% in June 2004 with women (4.6%) reporting more than men (3.8%). In Australia, social phobia is the 8th and 5th leading disease or illness for males and females between 15-24 years of age as of 2003.

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