NEW YORK (Reuters Health) – Consistent with some previous reports, the results of a case-control study suggest that depressive symptoms are an early feature of Parkinson’s disease, preceding the characteristic motor manifestations.

The results, which appear in the Journal of Neurology, Neurosurgery, and Psychiatry for June, indicate that initiation of antidepressant therapy is associated with a twofold increased risk of developing Parkinson’s disease in the next 2 years.

Although several reports have shown a link between depressive symptoms and Parkinson’s disease, it was unclear whether one caused the other or if both may arise from some common pathological mechanism, lead author Dr. A. Alonso and colleagues explain.

To look into these questions, the research team conducted a study involving a subset of patients included in the General Practice Research Database, which features longitudinal data on over 3 million Britons seen by general practitioners in the UK.

In the current analysis, 999 patients with Parkinson’s disease identified through records from 1995 to 2001 were matched by age, gender, and practice to 6261 controls. Initiation of antidepressant therapy was used as a marker for depressive symptoms.

Overall, subjects who began antidepressant therapy were 85% more likely to develop Parkinson’s disease than were non-initiators, Dr. Alonso, from the University of Minnesota School of Public Health in Minneapolis, and colleagues note. Further analysis showed that the association was strongest in the 2 years after starting such therapy, yielding a rate ratio of 2.19. Beyond 2 years, the rate ratio fell to 1.23.

Further analysis showed that the strength of the association was similar whether selective serotonin reuptake inhibitors or tricyclic antidepressants were used.

“The observed association between antidepressants and Parkinson’s disease risk could have implications for clinical practice,” the investigators conclude. “Depressive patients that start developing motor symptoms should be promptly evaluated to rule out a diagnosis of Parkinson’s disease.”

Reference:
J Neurol Neurosurg Psychiatry 2009;80:671-675.