Objective: This paper reviews the main neuropsychiatric disorders associated with Parkinson's disease (PD) and describes the neuropathological hypothesis proposed to explain these symptoms.
Development: This disease is usually associated with neuropsychiatric complications such as depression, anxiety and apathy. Besides, psychiatric symptoms are one of the most common side effects of antiparkinsonian drug-therapy.
Conclusions: Depression is the most frequent emotional disorder reported in patients with PD. Up to 20% of parkinsonian patients meet DSM-IV criteria for major depressive episode and another 20% for dysthymia, while the prevalence of depression in normal aged population is about 2-8%. The relationship between PD and depression has not been fully established. Some investigators have suggested that depressive symptoms in PD are causally related to the underlying neuropathological process, affecting predominantly serotoninergic and dopaminergic pathways. Alternatively, depression in PD may represent a normal reaction to the progressive physical impairment induced by the disease. Otherwise, up to 20% of parkinsonian patients present levodopa-induced psychiatric complications. Visual hallucinations are the commonest, but delusions, confusional states, sexual disorders and sleep disorders have also been described. Serotonin and dopamine have been implicated in the neuropathological basis of these disorders.