The authors consider the general conception of the pathogenesis of mental diseases based on the disruption of interactions between local neuronal networks. The development of mental disorders provoked by environmental factors is thought to disturb the activity of small groups of neurons with genetically determined module activity. It is hypothesized that the interaction of modules determines the forms of this activity that are of evolutionary origin predicting behavioral programs of familial inheritance and “personified” behavioral response. In this case, possibilities of pharmacological treatment of mental disorders are limited by the modulation of neurochemical processes controlling more simple fragments of behavioral response. This should be taken into consideration in the development of new psychopharmacological medications.