the measure or diagnostic criteria [24, 55]. For example, concerns about the high rates of false positives in many population-based studies using DSM-III and DSM-III-R led to the addition of a clinical significance criterion for most specific disorders of DSM-IV that required a greater emphasis on clinical distress or impairment for case definition. As a result of the introduction of this criterion, most population- based epidemiologic studies that used the DSM-IV criteria observed much lower rates of psychiatric disorder than previously obtained in prior DSM-III-R studies (ranging from 17 to 20%) [12, 19, 34, 35, 41]. Prevalence rates of child psychiatric disorders also vary depending on the type of informant ascertained (i.e. parent, child or teacher) [42], the age of the child [11, 14], how data provided by different informants (i.e. parent, teacher or child) are combined [48] and whether or not impairment is used in the definition of a case [19, 71].
