Studies in recent years have significantly widened our understanding of the mechanism of action of brain-derived neurotrophic factor (BDNF) and the potential areas of its application. This review presents results from our own studies, along with published data on the influences of BDNF on epigenetically and genetically determined behavioral disorders. Particular attention is paid to the role of the genotype and the involvement of the brain serotonin system in the effects of BDNF. The material presented in this review provides evidence that: 1) the key genes of the brain serotonin system (tryptophan hydroxylase 2, 5-HT 1A and 5-HT 2A receptors) are involved in the mechanism of action of BDNF; 2) single central doses of BDNF have long-lasting positive influences on several genetically determined manifestations of pathological behavior; 3) BDNF can weaken the manifestations of behavioral disorders induced by harmful environmental factors acting during the prenatal period.