Prenatal Lead Exposure Linked to MDD, Anxiety Symptoms in Later Life
Key Clinical Summary
- Late prenatal lead exposure, especially in the third trimester, was associated with nearly double the risk of major depressive disorder in older adulthood.
- No significant link was found between early lead exposure and generalized anxiety disorder, though some anxiety symptoms increased in later adulthood.
- Findings underscore a sensitive prenatal window for neurotoxic exposure with long-term mental health implications.
Early exposure to lead, particularly in the third trimester of pregnancy, was associated with a higher risk of major depressive disorder (MDD) and anxiety symptoms in later life, according to cohort study results published in JAMA Psychiatry.
“Early lead exposure is associated with psychological concerns in childhood, but less is known about sensitive periods of exposure or persistence into later adulthood,” wrote Joyce J. Y. Lin, PhD, Department of Environmental Health, Harvard T.H. Chan School of Public Health, Boston, MA, and study coauthors.
To better examine the impact of exposure on later mental health outcomes, researchers recontacted participants of the Saint Louis Baby Tooth —Later life Study (SLBT), who had donated baby teeth as children in the 1950s-1970s. Beginning in 2021, members of the cohort were asked to complete the Patient Health Questionnaire-9 (PHQ-9) and Generalized Anxiety Disorder Screener-7 (GAD-7) to assess depressive and anxiety symptoms. Their stored baby teeth were also analyzed for lead concentrations across prenatal and early postnatal periods.
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Of the 718 participants whose teeth were analyzed for lead, 695 and 697 completed the PHQ-9 and GAD-7, respectively. The cohort had a mean age of 62 (SD, 3.6) years and a median combined tooth lead concentration of 1.34 (95% CI, 1.02-1.82) ppm.
After adjusting for covariates, the researchers found that an interquartile range increase in combined tooth lead was associated with nearly 2 times the risk of depression in later adulthood (odds ratio, 1.90; 95% CI, 1.20-2.99). The most sensitive period for exposure appeared to be approximately the third trimester (odds ratio, 1.55; 95% CI, 1.23-1.97).
Though there was no association between early lead exposure and major generalized anxiety disorder in later adulthood, both late prenatal and postnatal lead exposure were associated with greater later adulthood anxiety symptoms.
“These findings emphasize the importance of factoring in later life health outcomes when considering the benefits of lead exposure interventions in childhood and suggest investment in screening and mental health services may be needed to address the long-term burden of historical lead exposure,” the authors wrote.
To extend on these findings, the researchers suggest that follow-up studies in this cohort employ broader mental health screenings that account for chronic symptoms and disorders in other domains.
