[Comorbidity of depression and nonaffective - schizophrenia spectrum disorders: the clinical-epidemiological study...

To explore the association between depression and heterogenic nonaffective symptom complexes in the study EDIP (Epidemiology of Depression and nonaffective Psychiatric disorders).

The study consisted of two stages. The first stage (91 patients) aimed to resolve organizational and methodological issues, the second stage was performed in the epidemiological sample of 705 patients.

The heterogeneity (inequivalence and bidirectionality) of associations between depression and heteronomous nonaffective disorders have been identified. The associations are distinguished in three types: 1) affinity (agonism); 2) repulsion (antagonism); 3) lack of selective interaction (inertness) between depression and nonaffective disorders. The results obtained are discussed in a context of two conceptually polar psychopathological models of comorbidity between depression and nonaffective disorders: 1) based on a nosological dichotomy «affective disease - schizophrenia» and 2) denying the abovementioned dichotomy. The first model places depression among disorders of a mild psychiatric register. The second model supposes the integration of depression with syndromes typical for schizophrenia in a common "affect-symptoms" space and considers the increase of depression frequency proportionally to duration and severity of schizophrenia. Our own results have shown that depression is observed not only among disorders of mild psychiatric registers, but also in schizophrenia, though with a significantly lower frequency (as a nonobligatory compound of a syndrome). Thus, depression influence in comorbid delusional, schizophrenic and other severe nonaffective disorders is greatly diminished.