Depression and anxiety are common mood disorders associated with Parkinson’s disease (PD). Among environmental factors, organophosphate (OPs) pesticide exposures have been previously linked to depression as well as to PD. Here we not only re-examine the relationship between depression and anxiety prior to PD onset, but for the first time are also considering whether OPs pesticide exposure modifies this association. From 2001 to 2015, we recruited 832 PD patients diagnosed early in the disease and 817 unaffected population controls from three counties in central California. We collected information about depression and anxiety diagnoses and psychotropic medication use prior to PD onset, and also generated ambient residential and/or the workplace address measures of OP pesticide exposures based on a geographic information system derived agricultural pesticide exposure report system. Employing logistic regression models, we analyzed the association between depression/anxiety and PD adjusting for sex, age at diagnosis/interview, race, smoking, and education. Risk of PD was increased among those diagnosed with depression/anxiety and medication use prior to PD diagnosis (ORdepression & anxiety & medication use = 1.73, 95% CI = 1.37-2.18), and the estimated effect sizes increased with depression/anxiety diagnoses being closer to the time of PD diagnosis, especially in males. While not formally statistically significant, OP exposures seemed to modify the size of the effect estimate for a depression/anxiety diagnosis and PD and the joint effects of depression/anxiety and OP pesticide exposures together were very large in males (ORFrequent exposure + Received depression and/or anxiety diagnosis = 5.00, 95%CI = 2.54-9.87).

These results further support the notion that depression and anxiety might be early symptoms in the prodromal phase of PD and that in males OP exposures may contribute to mood disorders prior to PD onset.