Depression in Parkinson's disease

Depression occurs in 40% to 50% of Parkinson's disease (PD) patients. From research over the last decade, this co-occurrence appears to be more than an emotional reaction to disability. Replacement of the neurotransmitter, dopamine, benefits the PD motor functions, and the neurotransmitter, serotonin, in antidepressants, reduces depressive symptoms. However, identification of the physiological linkage between PD and depression continues to evade research efforts.