Pesticides, depression and suicide: a systematic review of the epidemiological evidence

It has been suggested that high exposure to pesticides, including poisoning, experienced by agriculture workers and rural residents may result in an elevated risk of psychiatric disorders and suicidal behavior. Epidemiological data supporting this hypothesis are very limited. An updated systematic review was conducted in epidemiologic literature on the relationship of pesticide exposure with depression and suicide published over the last 15 years by using MEDLINE database. A total of 11 studies on depression and 14 studies on suicide met inclusion criteria. Depression or other psychiatric disorders have shown increased risks associated with previous pesticide poisoning in 5 studies, with statistically significant odds ratios (OR) ranging from 2.08 to 5.95. Lower risk estimates have been found for chronic pesticide exposure. Among studies on suicide, 4 reports found increased suicide rates in areas with intensive pesticide use (OR between 1.60 and 2.61) compared to areas with lower pesticide use. Occupation in agriculture has shown a significant association with higher suicide risk than other occupational groups in 4 studies (OR between 1.30 and 4.13), but not in one recent report. Regarding specific pesticides, lifetime use of chlorpyrifos was related with increased suicide mortality (OR=2.37) in one study. Scientific evidence of association between pesticide exposure and either depression or suicide has been shown in some populations, in studies using varying epidemiological approaches, but is still very limited and inconclusive. Review of the literature warrants further research to explore such relationships, in particular prospective studies among large samples of high- and low-dose-exposed workers, using detailed exposure assessments, and evaluating other potential sources of psychological stress.