Depression in Parkinson's disease.

Depression in Parkinson's disease (PD) is a common complication, with a major impact on quality of life. Failure to recognize and treat depression can lead to premature and inappropriate discontinuation of antiparkinsonian therapies. Cited frequency for depression in PD varies between 2.7 and 70%. Methodological differences account for much of the disparity. The aetiology of depression in PD is complex, with 'tonic' (slowly changing and persistent) and 'phasic' (short-lived and fluctuating) components. Both depression and anxiety may predate the onset of the motor disorder by some years. Hedonistic homeostatic dysregulation is a cyclical mood disorder associated with excessive intake of dopaminergic therapies, inappropriate for the motor state. Negative affective symptoms occur on attempted reduction of medication, reinforcing the abnormal medication pattern. The Montgomery-Asberg Depression Rating Scale and the Hamilton Rating Scale for Depression have good diagnostic sensitivity and specificity for assessing depression in PD. There is a dearth of sizeable, placebo-controlled studies for evaluating drug treatment of depression in PD. Dopaminergic drugs have variable antidepressant properties. Selective serotonin reuptake inhibitors are currently the most commonly prescribed group of antidepressants in the depressed PD patient. Depression in the PD patient may be associated with a more rapid deterioration in cognitive and motor functions.