[Molecular biology of depressive disorders]

Heritability of major depression from twin studies is estimated as -40% that is relatively small as compared with -80% for schizophrenia and -90% for bipolar affective disorder. It suggests that genetic as well as environmental factors contribute to the aetiology of major depression. Approximately 800 association studies on candidate genes of depression have been published, and among them, several genes were confirmed as risk for vulnerability to major depression by meta-analyses. Recent investigations on pathophysiology of depression have focused on hippocampus as a modulator of Hypothalamus-Pituitary-Adrenal (HPA) glands axis. Molecular biological studies on the interaction between stress, hippocampus and HPA axis reveal glucocorticoid and brain-derived neurotrophic factor(BDNF) are key molecules developing and recovering from depressive disorder.