Mood Disorder in Parkinson's Disease

Abstract

Depression is found in about 40% of patients with Parkinson's disease (PD). The main characteristics of depression in PD is inability to experience pleasure, however, the symptoms such as severe anxiety, suicidal idea, daily fluctuation of mood, depression associated hallucination and delusion are relatively rare. In more than half of these patients, the cause of depression is closely linked the pathophysiology of PD itself. The feature of depression in PD is limited and is equivalent for the words of anhedonia/apathy, although the feature of "depression" is also occasionally found in PD. Indeed, recent studies suggested the features of depression, apathy (anhedonia) and dementia were independent in PD. As the mechanism of anhedonia/apathy in PD, the disturbance of acetylcholine and other monoamine system such as noradrenaline as well as dopaminergic system is indicated. The dopamine system that concerns with anhedonia/apathy is considered to be originated from ventral tegmental area in the midbrain project to nucleus accumbens, amygdala and mesolimbic system. Malfunction of these neurons cause the inactivation of emotion and motivation as the disruption of frontostriatal circuits, and this is related to the anhedonia/apathy in PD. Moreover, recent studies have shown that the dysfunction of amygdala and the disruption of its connectivity in the brain is suggested to the etiology of depression in PD. In the treatment of depression, at first, the sufficient medication for motor symptoms is needed, because depression in PD is linked the pathophysiology of PD. In the next step, anti-depressants are used. Some dopamine agonist such as pramipexole is also effective.