Two new research studies focused on PARKINSON’S DISEASE and Depression were published recently. One studies the increased risk of developing PARKINSON’S DISEASE after bouts of treatment resistant depression. The second study was an analysis of several studies of antidepressant medications used in PARKINSON’S DISEASE.
Depression is a serious risk in people with PARKINSON’S DISEASE; some studies have shown that as many as 60% of people with PD are depressed.. The first study looked at 10 years of records and found correlations between age of onset of depression and development of PD. In younger patients, depression did not always lead to PARKINSON’S DISEASE, however more senior patients were twice as likely to be diagnosed and seniors whose depression did not respond to treatment were found to be three times more likely to develop PD.
While this study is not proof-positive that depression necessarily leads to PARKINSON’S DISEASE, the correlation does bear serious weight for future research. It may be that depression could be an early symptom or biomarker, like loss of the sense of smell; but since 60% of people with PARKINSON’S report feeling depressed, it may simply be a symptom. One limitation of this study was that the population studied did not provide any information about family history or other environmental factors. These factors will need careful evaluation in future studies.
The second study examined the effects of common antidepressant treatment in PARKINSON’S DISEASE. They based their study on 11 clinical trials of treatment for depression in Parkinson’s disease held between 1986 and 2013. These trials used medications that are standard treatment for depression in PD as well as standard treatments for PD that have shown efficacy for treating depression. These medications included Tricyclic Antidepressants (TCAs), Selective Serotonin Reuptake Inhibitors (SSRIs), Serotonin and Norepinephrine Reuptake Inhibitore (SNRIs) and Dopamine agonists, which have also been promoted as relieving depression in PD.
The research was very thorough, examining not only the effect on depression, but also on troublesome side effects, such as nausea, dry mouth, headache, dizziness, hallucinations, somnolence and excessive dyskinesias. They also compared the rating scales used to evaluate depression. Their basic findings were that dopamine agonists were no more effective than placebo in relieving depression, and sometimes had more serious side effects. SSRIs and SNRIs were used as a first choice to avoid the side effects of tricyclic antidepressants, such as dry mouth, dry eyes and constipation.
Ultimately, it was found that tricyclic antidepressants were more effective than SSRis or SNRIs, and were often very well tolerated, suggesting that tricyclic antidepressants might well be a better first choice for depression in PD.
The authors caution that this study has several serious limitations, such as the age of the participants and the stage of the disease. Motor fluctuations and other co-morbidities and medications also need to be accounted for. Larger studies are needed to clarify and confirm the data that this early study has begun.
- C.-C. Shen, S.-J. Tsai, C.-L. Perng, B. I.-T. Kuo, A. C. Yang.Risk of Parkinson disease after depression: A nationwide population-based study. Neurology, 2013; DOI:10.1212/WNL.0b013e3182a956ad
- Liu J, Dong J, Wang L, Su Y, Yan P, et al. (2013) Comparative Efficacy and Acceptability of Antidepressants in Parkinson’s Disease: A Network Meta-Analysis. PLoS ONE 8(10): e76651. doi:10.1371/journal.pone.0076651