Insomnia in relation to depression and anxiety: epidemiologic considerations.

Epidemiologic studies show that psychopathology is a very powerful risk factor for the occurrence of insomnia. Depression and/or anxiety are quite prevalent among insomniacs, while insomnia is more than twice as prevalent in depressed than in non-depressed individuals. Moreover, recent data support a strong causal link of insomnia to both depression and anxiety. An exact cause-and-effect relationship between insomnia and psychopathology, however, has not as yet been definitively established. This is probably due to methodological differences across studies, related to design characteristics and the ways insomnia as well as various dimensions of psychopathology have been defined and detected. Thus, more refined psychometric techniques and multivariate methods of analysis should be utilized to elucidate the etiologic interface of insomnia and psychopathology.