Purpose of review: Clinical studies support a bidirectional link between depression and neurological diseases. Here we review the most recent findings supporting the hypothesis that major depression is a medical illness of the brain which can be elicited by neurological illnesses.
Recent findings: In the last year major improvements in brain-imaging techniques allowed correlations to be demonstrated between functional and structural brain abnormalities in specific brain areas (prefrontal cortex, hippocampus, cingulate gyrus) and the presence and severity of affective disorders, thus suggesting a neural basis for their onset and progression. Similar lesions, caused by neurological diseases, have been found to correlate with the presence of depression in neurological illnesses, but literature on the topic is still lacking. Depression in neurological disorders responds to the same treatments available for idiopathic major depression, but patients seem to have different sensitivities to side effects depending on their specific neurological syndrome. Most available data come from case reports and open trials.
Summary: 'Psychiatric' and 'neurologic' depression seem to share common abnormalities in specific brain areas, but sound brain-imaging studies of the neural correlates of depression in neurological disorders are still lacking. Available treatments are efficacious, but no clear-cut guidelines about the best drugs and dosages can be defined because double-blind placebo-controlled studies are still scarce.