Parkinson's disease and depression

During the past decade investigators paid increasing attention to psychomotor retardation and "volitional inhibition" as central elements of thinking and action in depression. In line with this is an increasing appreciation of some striking clinical parallels between particular aspects of Parkinson's disease and psychomotor manifestations of melancholia. We provide an update of the clinical literatur regarding diagnostic problems and phenomenology of depressive states in Parkinson's disease and review their relation to cognitive impairments in neuropsychological task performance. We emphasize that many divergent results in older studies concerning Parkinson's disease and depression can be explained by methodological differences and shortcomings. Although the genesis, course, and treatment responsiveness of depressions in Parkinson's disease are still only partially understood, consensus regarding frequency and symptom features is gradually beginning to grow. Recent studies have shown that the occurrence of moderate to severe depressive states meeting the DSM-III-R criteria for Major Depressive Episode in community-based populations of Parkinson's disease patients is considerably lower (less than 10%) than the results of previous studies had suggested. However, a substantial proportion of predominantly younger patients have less severe but clinically significant depressive symptoms. Depression in Parkinson's disease patients is frequently associated with cognitive impairment. The issue of complex relationships between depression and primary, disease-related cognitive dysfunction in Parkinson's disease patients is dealt with in greater detail.