A federally funded study led by Brown University researchers links increased childhood blood lead concentrations with increased depressive symptoms in adolescence, with larger increases when exposure occurred later in childhood.
PROVIDENCE, R.I. [Brown University] - While lead exposure in children has been associated with cognitive and behavioral problems, few studies have examined later psychiatric symptoms. A new analysis led by researchers at Brown University's School of Public Health found that increased concentrations of lead in the blood during childhood were associated with increased depressive symptoms in adolescence.
The research, which was funded by federal grants from the National Institutes of Environmental Health Sciences and published in JAMA Network Open, underscores the long-term behavioral outcomes associated with early environmental exposures, the researchers said. Exposure levels at age 8 seemed to be particularly significant.
"We found compelling associations suggesting that lead exposure throughout childhood is associated with depressive symptoms," said study author Christian Hoover, a student in the Ph.D. program in epidemiology at Brown's School of Public Health. "In addition, it appeared, based on our results, that there was a pattern where age 8 was a really consequential time in terms of a child's exposure and an association with developing onset and severity of depressive symptoms."
Lead is a neurotoxicant impacting cognitive and behavioral functioning, and research has shown that any exposure is associated with adverse health outcomes in children and adults. Despite the reduced uses of lead in the U.S., children are still exposed through environmental sources like dust, soil and drinking water from aging pipes. Few studies have evaluated relatively low blood-lead measures throughout childhood in association with child depression and anxiety. This is concerning, the researchers said, given that these psychiatric conditions are prevalent among U.S. adolescents.
To address that knowledge gap, the researchers analyzed the data of 218 pairs of caregivers and children in the Health Outcomes and Measures of Environment Study, which followed children and their families from the second trimester of pregnancy to age 12 years, assessing associations of environmental toxicant exposures with various health outcomes, and at around age 12, assessing anxiety and depression. The researchers also measured blood lead concentrations at the ages of 1, 2, 3, 4, 5, 8 and 12 years.
They found that each doubling in mean childhood blood lead concentrations was associated with increased risk of elevated child-reported depressive symptoms. Low levels of childhood blood lead concentrations were associated with self-reported depressive symptoms in later childhood, with particularly large increases in risk when exposures occurred in late childhood and early adolescence.
The researchers hypothesized that several biological mechanisms could explain how lead exposure may be associated with psychiatric illness, including through altered neurotransmitter function, reduced neurogenesis and disrupted synaptic plasticity, particularly in brain regions associated with mood regulation. Other proposed mechanisms include oxidative stress, inflammation and genetic modifications that may contribute to the onset and persistence of mental health symptoms after lead exposure.
"These findings suggest that low-level lead exposure during childhood and adolescence is associated with mental health in later childhood, highlighting the need for continued efforts to prevent lead exposure and the need to reduce lead exposure in older children," said study author Joseph Braun, a professor of epidemiology and the director of Brown's Center for Climate, Environment and Health.
Future studies should continue to explore how to prevent cumulative or later-childhood lead exposure and whether distinct long-term patterns of lead exposure may be associated with child mental health outcomes, the researchers concluded.
This research was funded by grants from the National Institutes of Environmental Health Sciences (P01 ES11261, R01 ES01457, R01 ES020349, R01 ES025214, R01 ES027224 and F31ES036867).
