Depression in Parkinson's disease: impediments to recognition and treatment options

By some estimates, nearly half of patients with PD also suffer depression. Because features of PD frequently overlap with typical manifestations of major affective disorder (or mild dysthymia), both diagnosis and treatment of this comorbidity are challenging. Some of these interactive features include cognitive and speech deficits and impairments in emotional expression (e.g., PD-related facial masking) or processing. Parkinsonian depression probably is caused by an independent abnormality rather than as a maladaptive response to disease, in that the degree of depression is not correlated with PD severity. Prognostically, depressive features (e.g., introversion, inflexibility) may represent a subtle premorbid state heralding the onset of PD or an accelerated cognitive decline thereafter. Therapeutic mainstays for parkinsonian depression include psychosocial counseling at the time of PD diagnosis (and during advanced stages of PD) as well as appropriate medication regimens, the relative clinical efficacy of which remain a matter of ongoing clinical inquiry: levodopa, dopamine agonists, selegilene, tricyclic antidepressants, and selective serotonin reuptake inhibitors). This review formulates a rational treatment algorithm to assist in clinical management of parkinsonian depression, an enormously complex clinical entity.