Depression: An Indication of Parkinson’s Disease
By editor | May 15, 2007
Parkinson’s disease (also known as Parkinson disease or PD) is a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech.
The possibility of an ‘organically’ based depression intrinsic to the path physiology of Parkinson’s disease (PD) and comparable to endogenous depression (Major Depressive Episode) has been raised. It has also been argued that signs of depression observed in PD are merely the natural reaction of the patients to their progressive and inevitable physical limitations and loss of independent function Because conventional depression rating scales are limited in scope, a psychometric investigation of depression in PD was pursued
Based on the known impairment of short-term memory (STM) in endogenous depression, which was confirmed in a group of psychiatric patients in the present study, measures of STM were also obtained in groups of depressed and no depressed PD patients and in 15 normal control subjects.
Regardless of depression severity, PD patients performed as well as control subjects and both these groups consistently obtained scores significantly better than those of the endogenously depressed patients A relative weakness in the PD patients on order-dependent STM tests was further explored and interpreted as an indication of mild frontal lobe dysfunction
Depressive symptoms occur in about 45% of patients with Parkinson’s disease (PD). They reduce subjective and objective quality of life independent of motor deficits. Diagnosis of depression in Parkinson’s disease patients relies particularly on subjectively experienced symptoms, including anhedonia, the reduced capacity to experience pleasure.
It has been postulated that experiencing joy and pleasure depends on dopaminergic reward mechanisms in the limbic system, which are thought to be the basis of motivation, drive, and activation. In Parkinson’s disease, degeneration of dopaminergic neurons involves motor structures, including basal ganglia, but also structures of the limbic system. Degenerative processes in Parkinson’s disease may affect dopaminergic reward mechanisms and lead to anhedonia, loss of motivation, avolition and apathy. These pathophysiological mechanisms could explain effects of pramipexole, a novel dopamine agonist, on anhedonia and depression found in animal experiments and patients with major depressive disorder.
Anhedonia, a core symptom of depression, correlates with motor retardation in patients with major depressive disorder. Anhedonia has been assumed to be a frequent symptom in depressed patients with Parkinson’s disease. Like in major depressive disorder, anhedonia may also have an impact on motor functioning and activities of daily living in Parkinson’s disease. However, to our knowledge, no data exist regarding frequency and relevance of anhedonia in Parkinson’s disease.
Therefore, the aim of this open study was to investigate depressive symptoms in Parkinson’s disease and test the hypotheses that anhedonia is more frequent in patients with Parkinson’s disease compared with healthy comparison subjects, that anhedonic patients with Parkinson’s disease show more severe parkinsonian symptoms compared to nonanhedonic patients and that anhedonia is reduced during treatment with pramipexole.
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