[Depression and Parkinson syndrome]

Depressive mood is frequently associated with Parkinson's syndrome, but it may also occur as a precursor of this disease. As regards the subtypes of Parkinson's disease, the frequency of depressive states is significantly higher in the type dominated by akinesia and rigidity than in the type dominated by tremor. On the basis of biochemical changes, certain aspects of the depression can be successfully treated by substitution therapy: L-dopa medication may increase the reduced dopamine values in the striatum, thereby improving drive. Substitution with L-tryptophan raises the lowered serotonin values in the reticular formation, which may influence sleep disturbances. The changes of basic mood, however, which are characteristic of depression, such as cheerlessness and apathy, are the dopamine of antidepressive medication; only these drugs can re-establish the biochemical balance to a large extent.