Recent studies point to the importance of frontal systems in the control of complex behavior. Because major depression affects the same systems the considerable overlap between some so-called "depressive symptoms" and the behavioral sequelae of frontal lobe brain damage can be explained. In other mental disorders, functional outcomes are closely related to frontal system impairment. Frontal deficits, rather than mood disturbance, may explain the disability of depressed patients. This should cause doctors to reconsider their approach to depression. Treatment for the cognitive aspects of depression may be needed to ensure improvement in functional domains.