With this preamble in mind, in this paper, we review the literature on prevalence rates of DSM-III-R and DSM-IV CD and ODD across cultures, age, and ethnicities as evidenced by epidemiologic studies carried out in probability community or school samples. We excluded from our review findings treatment samples since they can be biased due to selection effects [20]. Bias can arise because clinical studies tend to focus on persons with more chronic and severe manifestations of the disorder. If selection bias is ignored, the estimates of prevalence, patterns of correlates, co-morbidity and impairment can be affected by statistical bias known as Berkson’s bias [5, 9].
