Occurrence of depression and anxiety prior to Parkinson's disease.

OBJECTIVE: To assess the relationship between depression and anxiety and Parkinson's disease (PD).
BACKGROUND: Many people with PD suffer from depression and anxiety prior to the onset of motor symptoms. Studies suggest these psychiatric conditions may be risk factors for PD or prodromal non-motor symptoms.
METHODS: Using a population-based approach in three California counties, we recruited 371 incident PD cases, 402 population and 115 sibling controls. We recorded self-reports of lifetime depression/anxiety diagnoses and use of psychotropic medications. We adjusted for age, race, sex, pack-years of smoking, and education, and also conducted analyses after excluding (lagging) both diagnoses and medication use first occurring within 2, 5, 10, and 20 years of the index/diagnosis date.
RESULTS: Cases were more likely to have received a diagnosis of depression or anxiety at any time prior to index date (OR 1.42, 95% CI 1.01, 2.00), but were not more likely to have been both diagnosed and treated (OR 1.11, 95% CI 0.77, 1.60). Male PD patients received diagnoses combined with treatment more often than population controls within 5 years of PD diagnosis (OR 2.21, 95% CI 1.21, 4.04; 2 year lag: OR 2.44, 95% CI 1.29, 4.61; 5 year lag: OR 1.67, 95% CI 0.80, 3.49). We did not see any differences for females. Results for cases compared to sibling controls were similar to those for population controls.
CONCLUSION: These results suggest that depression and anxiety may be early symptoms during the prodromal phase of PD.