Psychosis and depression are syndromes that affect the most basic human processes of perception and judgment. Traditional dichotomous classification of psychotic and affective disorders resolved in strict separation between schizophrenia on one hand and bipolar disorder and recurrent depressive disorder on the other hand. However, it is not uncommon that depression and psychosis as
syndromes are expressed together in the course of the same mental disorder.
According to recent knowledge on the molecular level there are probably many multiple susceptibility genes involved in the pathogenesis of both psychotic and affective disorders, each of small effect, which act in conjunction with environmental factors. Research data indicates a significant overlap in genetic susceptibility across the traditional classification categories of psychotic disorders and affective disorders. It seems that a new classification and research approach will provide better understanding of severe mental disorders and explain the usefulness of some medications in different groups of these disorders
