Lead exposure during childhood appears tied to a significant increase in the risk of psychopathology in adulthood, results of a multidecade, prospective cohort study show.
“These results suggest that early life lead exposure in the era of leaded gasoline experienced by individuals who are currently adults may have contributed to subtle, lifelong differences in emotion and behavior that are detectable at least up to 38 years of age,” Aaron Reuben and his coauthors wrote in.
The ongoingin New Zealand has followed 1,037 individuals born during 1972-1973. Of these individuals, 579 were tested for lead exposure at 11 years of age. The study assessed their mental health at 18, 21, 26, 32, and 38 years of age.
“Although follow-up studies of lead-tested children have reported the persistence of lead-related cognitive deficits well into adulthood, apart from antisocial outcomes, the long-term mental and behavioral health consequences of early life lead exposure have not been fully characterized,” wrote, a PhD student in the department of psychology and neuroscience at Duke University in Durham, N.C., and his coauthors.
Researchers saw that, for each 5-mcg/dL increase in childhood blood lead level, there was a significant 1.34-point increase in general psychopathology (P = 0.03), which was largely driven by a 1.41-point increase in internalizing (P = 0.02) and 1.30-point increase in thought-disorder symptoms (P = 0.04). Those associations were seen after adjustment for covariates, such as family socioeconomic status, maternal IQ, and family history of mental illness.
Adults who had higher lead exposure during childhood also were described by their informants – close friends or family members – as being significantly more neurotic, less agreeable, and less conscientious. However, they showed no significant differences in extroversion or in openness to experience, compared with those with less lead exposure.
“These results suggest that early-life lead exposure in the era of leaded gasoline experienced by individuals who are currently adults may have contributed to subtle, lifelong differences in emotion and behavior that are detectable at least up to 38 years of age,” the authors wrote.
They noted that the size of the effect was around one-third the size of the associations seen between psychopathology and other risk factors, such as family history of mental illness and childhood maltreatment. However, the effects of lead exposure on adult psychopathology were similar to its effects on IQ and stronger than the associations seen between lead exposure and criminal offending.
The researchers also examined how early these psychopathology symptoms could be detected with use of parent- and teacher-reported measures of antisocial behavior, hyperactivity, and internalizing from 11 years of age. This showed that individuals with higher lead exposure scored higher on these measures even at 11 years of age, “suggesting that
Mr. Reuben and his associates cited several limitations. One is that the study used a cohort that was predominantly white and born in the 1970s. Also, as an observational study, it does not establish causality between lead exposure and psychopathology.
Nevertheless, they wrote, the study results suggest that adult patients who were exposed to high levels of lead as children might benefit from increased screening and access to mental health services.
The Dunedin study is supported by the New Zealand Health Research Council and the New Zealand Ministry of Business, Innovation, and Employment. This study was supported by several entities, including the National Institute on Aging, the U.K. Medical Research Council, the National Institute of Child Health and Human Development, and the National Institute of Environmental Health Sciences. The authors reported no conflicts of interest.
SOURCE: Reuben A et al. JAMA Psychiatry. 2019 Jan 23. .