A population-based study of blood lead levels in relation to depression in the United States.

PURPOSE

Lead is a known neurotoxicant. Several studies have suggested that occupational exposure to lead may lead to depression, anxiety and other psychiatric illness, but few studies have examined environmental lead exposure and depression. We evaluated the relationship between blood lead levels (BLL) and depression in a sample representative of the US population.

METHODS

We analyzed data from 4,159 adults ages ≥20 who participated in the 2005-2006 cycle of the National Health and Nutrition Examination Survey (NHANES). Depression was assessed by the Patient Health Questionnaire-9 (PHQ-9). Relative risks were calculated using Poisson regression, and odds ratios were calculated with ordinal logistic regression using SUDAAN, controlling for pertinent covariates.

RESULTS

The risk of depression was only slightly elevated with increasing blood lead levels when lead was modeled as a categorical variable, with adjusted relative risks of 1.16 (95% confidence interval (CI) = 0.99-1.36), 1.20 (CI = 1.07-1.36) and 1.16 (CI = 0.87-1.54) for 0.89-1.40 μg/dL, 1.41-2.17 μg/dL and >2.17 μg/dL, respectively, when compared to 0-0.88 μg/dL using Poisson regression. Similar results were obtained with ordinal logistic regression. Analyses using BLL as a continuous variable did not show a significant relationship with depression.

CONCLUSIONS

This cross-sectional study did not provide consistent evidence for an association between environmental lead exposure and depression within the investigated blood lead levels.