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[Comorbidity of anxiety and depression: epidemiologic perspectives].

The validity of diagnosis in psychiatry remains controversial. The new international classifications of mental disorders and the use of diagnostic criteria have allowed a marked improvement in the diagnostic process but the validity of the clinical entities is far from being strongly established. Epidemiological approach is a way among others which can offer new insights to that problem. During the recent decade, several community surveys have been conducted using quite similar methods and designs, referring to the same classification systems and using structured diagnostic interviews. A systematic collection of clinical signs and symptoms has found that, in the community, as well as in clinical setting, anxiety and affective disorders are frequently comorbid in the same subject. The concept of comorbidity has different meanings in a clinical or epidemiological sense. Results from several community surveys underline the importance of this phenomenon in various countries whatever the specific prevalence of anxiety and affective disorders could be. The most recent large study, the National Comorbidity Survey, has been undergone partly to address many questions concerning the comorbidity patterns between affective, anxiety and substance use disorders, their risk factors and influence on morbidity and health seeking process. Comorbidity is high between major depression and all different anxiety disorders, and to a much larger extent with generalized anxiety disorder. The distinction between pur and comorbid disorders on one hand, primary and secondary disorders according to the sequence of age of onset in comorbid disorders on the other hand has been also underlined recently. Comorbidity between anxiety and affective disorders strongly argue for investigating the genetics as well as the psychosocial factors involved in this phenomenon. Within this methodological perspective, these studies may offer new answers to major problems encountered in clinical and psychopathological research and, by the way, improve current therapeutic strategies.