Psychological factors affecting neurological conditions. Depression and stroke, multiple sclerosis, Parkinson's disease, and epilepsy.

As a contribution to the proposed revision of the DSM-III-R category "Psychological Factors Affecting Physical Condition" for DSM-IV, this article reviews the history of how the relationship of psychiatric illness to neurological illness has been understood with respect to depression. Since both psychiatric and neurological illness are aspects of brain functioning, any statement of the relationship of these categories entails certain epistemological assumptions, some of which have undergone considerable change and rapid evolution in the course of the last century.