Both primary and secondary mood disorders may involve abnormalities in specific fronto-subcortical neuro-anatomic circuits. Abnormalities in these brain regions or in contiguous areas that can affect the connections between these regions could reflect malfunction of these circuits, associated with development of mood disorders. Alternatively, abnormalities in these circuits could confer vulnerability to mood disorders, and its onset could be determined by interactions with environmental and genetic factors. Deficits during brain development due to these factors could result in under-development of particular brain areas, which could be related subsequently with mood disorders. The aging process or pathology such as vascular brain disease could result in atrophy of some of these regions. Thus, the influence of genetic, environmental, developmental, and degenerative factors during the development of these brain structures may determine the onset of mood disorders .