Environmental pesticide levels in relation to depression in a population-based sample of adults

Several studies have suggested that high-level occupational exposure to pesticides may lead to depression, anxiety and other psychiatric illness, but few studies have examined lower-level environmental exposures and depression. We analyzed data from 1,381 adults aged 20 years and older who participated in the 2005–2006 cycle of the National Health and Nutrition Examination Survey (NHANES) and had complete data on pesticide exposure and depression. Depression was assessed by the Patient Health Questionnaire-9 (PHQ-9) and analyzed as an ordinal outcome: not depressed (score 0–4), mildly depressed (score 5–9) and moderately/severely depressed (score 10+). Urinary pesticide levels (2,5-dichlorophenol, O-phenyl phenol, 2,4-dichlorophenol, 2,4,5-trichlorophenol, 2,4,6-trichlorophenol), primarily reflective of herbicide and fungicide exposure, were examined as categorical variables based on quartiles (or 50th and 75th percentile, depending on variability) of the distribution of exposure in the population. Odds ratios (OR) were calculated with ordinal logistic regression accounting for appropriate sampling weights and the complex survey design. We controlled for age, gender, ethnicity, education, poverty-income ratio (PIR), and urinary creatinine levels. The prevalence of any depression was about 20%, which was higher among non-white, lower educated, and poorer individuals. The risk of depression was not associated with urinary pesticide levels for any of the pesticides assessed, with OR estimates consistently around the null across categories of exposure. Therefore, this cross-sectional study does not provide evidence for an association between environmental pesticide exposure and depression. Further studies are needed to examine the pertinent duration, level, and class of pesticide exposure resulting in depression.