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Some Antidepressants Delay Need for Dopaminergic Therapy in Parkinsonís Disease

People with early-stage Parkinson’s disease (PD) who were taking certain types of antidepressants were able to modestly delay the need for medications, such as levodopa, to control the motor symptoms of PD.  The new research, published in the journal Movement Disorders, underscores the potential benefits of effectively managing depression in people with PD and suggests a possible role for the drugs in protecting the brain against the progression of PD.

Depression is a common symptom of PD, affecting up to half of all people who have the disease.  As a result, numerous studies have evaluated the safety and efficacy of antidepressants in people living with PD.  However, no studies in humans have examined what impact such drugs might have on the progression of PD itself.

Research conducted in animal models of PD has revealed a number of different mechanisms by which antidepressants might protect against PD, including delaying the death of the dopamine neurons lost during Parkinson’s.  In order to investigate whether evidence exists for a similar effect in humans, Katrina L. Paumier, Ph.D., along with members of the Parkinson Study Group Genetics Epidemiology Working Group led by Timothy J. Collier, Ph.D., of Michigan State University conducted a meta-analysis of a group of large studies of people recently diagnosed PD (diagnosed within the past five years), some of whom were on antidepressants.  Their goal was to determine whether being on antidepressants delayed the need for dopaminergic therapy, and whether the drugs impacted any other common measures of PD development, such as motor dysfunction or the presence of a tremor.

Results

  • Of 2064 people included in the studies, 451 of them (22 percent) were taking an antidepressant.
  • In general, participants taking antidepressants actually began their PD medication sooner than those who were not taking antidepressants.
  • However, for people taking a specific type of antidepressants called tricyclics, which include amitriptyline, the time until individuals began PD medication therapy was modestly delayed compared to people not on antidepressants.
  • Atypical antidepressants such as bupropion, mirtazapine, and trazadone were also associated with delayed treatment with PD medications.
  • Baseline antidepressant use of any type did not significantly change other measures of PD progression such as tremor or motor function.

What Does It Mean?

Because many people with PD also have depression, the relationship between the treatments for depression and PD is of great interest.  The results of this study suggest that it is possible for certain classes of antidepressants to modestly delay the need for PD therapy.

However, it remains unclear whether tricyclic and atypical antidepressants delay the need for dopaminergic therapy because they protect the brain from cell death or because of a reduction in depressive symptoms.  In particular, previous studies have shown that people with Parkinson’s who are also depressed, report their PD symptoms earlier and have a lower quality of life, which may lead to earlier dopaminergic therapy.

The lack of an effect of antidepressants on other measures of PD progression, such as motor function or amount of tremor, supports the interpretation that antidepressants work by reducing depression and improving quality of life.  Unfortunately, the studies analyzed as part of this research did not measure changes in depression at the end of each study.  Although animal studies have shown a protective effect of antidepressants in the laboratory, more research over a longer time scale will be needed to determine whether the drugs play a similar role in humans.

In summary, this study reinforces the notion that depression and anxiety should be treated in people with PD, either because symptomatic depression improvement delays the need for PD medications or because these medications may actually be neuroprotective.  Further research is required to explore the mechanism by which some antidepressants may be more helpful than others.


Reference: Paumier, K.L., Siderowf, A.D., Auinger, P., Oakes, D., Madhavan, L., Espay, A.J., Revilla, F.J., Collier, T.J., for the Parkinson Study Group Genetics Epidemiology Working Group (2012). Tricyclic Antidepressants Delay the Need for Dopaminergic Therapy in Early Parkinson’s Disease. Movement Disorders, DOI: 10.1002/mds.24978.

Source Date: May 22 2012