Neuroimaging studies of mood disorder effects on the brain.

Studies of early-onset recurrent depression, late life depression associated with neurologic disorders, and bipolar illness have revealed structural brain changes within a neuroanatomical circuit. This circuit, originally described by, has been termed the limbic-cortical-striatal-pallidal-thalamic tract and is comprised of structures which are extensively interconnected. In three-dimensional magnetic resonance imaging studies of affective illness, many of the structures that comprise this tract have been found to have volume loss or structural abnormalities. Mechanisms proposed to explain volume loss in depression include glucocorticoid neurotoxicity, decreased brain-derived growth factor, decreased neurogenesis, and loss of plasticity.