Research Links Depression and Occupational Exposure to Pesticides

Research in the last decade has shown that high-level occupational exposure to pesticides can increase the risk of depression. Some studies have determined a significant association between long-term depression and pesticide poisoning, although the length of exposure time and amount that might result in depression is not clear. Much of the data suggests that high level exposure would be required, but some researchers have made a case for chronic low dose exposure as well. In order to examine the relationship between pesticide exposure levels and depression, a research team publishing in the journal Environmental Medicine looked at occupational exposure and depression in private pesticide applicators in North Carolina and Iowa.

The study population included 17,585 participants, mostly farmers with occupational exposure to pesticides. Out of that number, 534 participants reported physician-diagnosed depression. Five categories were established to quantify individual exposure levels. Low exposure was classified as 226 days or less, between 226 and 752 days was deemed intermediate, and greater than 752 days was considered high. The other two categories, an unusually high pesticide exposure event (HPEE), or physician-diagnosed poisoning, were unrelated to cumulative days of use.

Results of the study demonstrated that incidence of HPEE or pesticide poisoning meant a significantly increased risked of physician-diagnosed depression. After statistical adjustments, pesticide poisoning was found to be more strongly associated with depression than cumulative exposure or an HPEE. The median number of lifetime days of exposure was 370 days in people reporting either an HPEE or pesticide poisoning, and 225 days for those who did not report either of these events. When the authors included reported cases of HPEE and physician-diagnosed poisoning in their statistical model, even the highest cumulative exposure level could not be significantly associated with depression. However, when a subgroup that excluded pesticide poisoning was analyzed, high levels of exposure were significantly associated with depression. According to the authors, there is no way to determine whether or not the association between depression and high cumulative pesticide exposure may actually be a result of an unknown HPEE or poisoning, at least in some cases. It is reasonable to assume that an HPEE or poisoning event, combined with high cumulative exposure, can be associated with increased risk of depression.

The results of this study confirm earlier findings that associate symptoms of anxiety and depression with pesticide poisoning in individuals with occupational exposure. The fact that the study includes many cases of self-reported physician-diagnosed depression is a major strong point. In addition, the authors were able to obtain detailed information from participants, and use it to establish graded levels of exposure. The fact that all participants, including the study control group, were drawn from the same population is an additional strength.

Results from this study help to establish an association between depression and HPEE or pesticide poisoning, or chronic exposure in the absence of physician-diagnosed poisoning. Not enough is known regarding the neurologic effects of pesticide exposure, including the influence on depression and anxiety. The authors assert the importance of sensitivity on the part of the medical community to mood changes in patients with a history of occupational exposure to pesticides. The findings here suggest the importance of limiting pesticide applications. In addition to depression, overexposure to pesticides has been linked to other serious health concerns. As evidence on pesticide-related health problems continues to accumulate, it becomes clear that for the sake of humanity, minimum exposure combined with maximum protection should be an urgent priority.

Reference

Beseler, C., Stallones, L., Hoppin, J., Alavanja, M., Blair, A., Keefe, T., Kamel, F.

Depression and Pesticide Exposures among Private Pesticide Applicators Enrolled in the Agricultural Health Study

Environmental Health Perspectives, http://www.ehponline.org/

http://www.ehponline.org/members/2008/11091/11091.pdf