Consultation-Liaison Psychiatry

Psychiatric Issues in Neurology: Parkinson's Disease

Vice-Chairman, Department of Psychiatry Professor of Psychiatry, Medicine, and Surgery, Chairman, Consultation/Liaison Psychiatry, Virginia Commonwealth University Medical Center

First published in Psychiatry Weekly, Volume 2, Issue 41, on October 29, 2007

Psychosis

Parkinson’s disease is accompanied by dementia in a substantial minority of cases, and the boundary between Parkinson’s disease with dementia (PD-D) and dementia with Lewy bodies (DLB) is not a clear one. Psychotic symptoms (hallucinations and delusions) occur in 50% to 75% of patients with DLB, 30% to 50% with PD-D, and 5% to 15% with Parkinson’s disease without dementia. Hallucinations are usually visual and delusions are most often paranoid. While limited psychotic symptoms with retained insight in Parkinson’s disease have been regarded as benign, a recent study suggests this is not the case and that most individuals’ psychotic symptoms progress over a period of years.

In the early days of L-dopa treatment, adverse psychiatric reactions, particularly psychotic symptoms, were frequent after initiation of therapy and reported in up to 50% of patients after several years of treatment. The addition of carbidopa to L-dopa made this much less common. Psychotic symptoms have been reported as adverse reactions to other dopaminergic drugs in Parkinson’s disease, including bromocriptine, pramipexole, and ropinirole, but have not been clearly related to dose or length of exposure. Anticholinergics are beneficial for Parkinsonian symptoms but risk aggravating cognitive dysfunction if dementia is also present. Anticholinerigcs also may cause psychotic symptoms as part of delirium, whereas the hallucinations and delusions induced by dopaminergic drugs are usually isolated psychotic symptoms unaccompanied by delirium.

Typical neuroleptics, especially high-potency ones, are contraindicated in Parkinson’s disease because they exacerbate symptoms and block the effect of dopaminergic drugs. Clozapine is the only antipsychotic shown in a randomized controlled trial (that also included olanzapine and risperidone) to be effective against psychosis, without aggravation of Parkinson’s disease. Quetiapine appeared beneficial for psychotic symptoms without worsening Parkinson’s disease in an open trial, but two small randomized controlled trials were negative. Despite its mixed dopamine agonist-antagonist profile, open trials of aripiprazole have not supported its use for psychosis in Parkinson’s disease. While there are case reports of psychotic symptoms responding to cholinesterase inhibitors in patients who have PD-D, without aggravating Parkinson’s disease, others have reported they caused significant worsening of Parkinson’s disease motor symptoms (which is not surprising since anticholinergic drugs reduce Parkinson’s disease motor symptoms).

Depression

Depression is very common in Parkinson’s disease with a prevalence of up to 40% to 50%. For treatment of depression in Parkinson’s disease, tricyclic antidepressants may have the side benefit of reducing Parkinson’s disease motor symptoms because of their anticholinergic effects, but this must be balanced against the risk of their aggravating cognitive or autonomic dysfunction. Selective serotonin reuptake inhibitors have occasionally been reported to exacerbate Parkinson’s disease motor symptoms and rarely have caused extrapyramidal side effects in patients without Parkinson’s disease. Mirtazapine may be a good choice for depression in Parkinson’s disease and may even reduce symptoms of Parkinson’s disease. Finally, dopamine agonists such as pramipexole may be an alternative to antidepressants in Parkinson’s disease.

Disclosure: Dr. Levenson is on the advisory board for Eli Lilly.