Photo: amenclinicsphotos ac (Flickr)

Lead exposure is no joke. Especially in children. We already know it can lead to behavioral problems and learning disabilities as these exposed children age. Now, researchers have uncovered another potential impact: mental illness.

A study out Wednesday in the JAMA Psychiatry journal shows that early exposure to the toxic metal, which can be found in the paint and dust of old homes and even in local water supplies, is associated with increased mental illness in adulthood, including phobia, depression, mania, and schizophrenia. This study isn’t perfect by any means, but it did follow 579 people for more than 30 years and claims to be the “longest and largest” psychiatric follow-up on people who were exposed to and tested for lead in childhood.

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Unfortunately, these children were predominantly white kids from New Zealand’s southeastern city of Dunedin. That makes the findings difficult to generalize, particularly to the communities of color who are disproportionately burned with lead exposure in the U.S, explained Pam Factor-Litvak, an epidemiology professor at the Columbia University Medical Center who was not involved in the study. Still, that doesn’t diminish the study’s relevance or the need for further research.

“It’s one of the premiere cohort studies in the world,” Factor-Litvak told Earther of the Dunedin Multidisciplinary Health and Development Study, which has been tracking these people since they were 3. “All of the measures in this study, to my knowledge, have been done with extreme thought, and they’ve used state-of-the-art measures.”

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The authors, many of whom hail from Duke University, compiled assessments—including clinical interviews, medical records, and questionnaires from close friends and relatives—of these individuals, born between April 1972 and March 1973, to assess their mental health. The study is entering its next phase this year as the cohort turns 45, but this new study uses data up until they were 38.

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The level of lead exposure among the cohort ranged from 4 micrograms per deciliter to 50 micrograms per deciliter with a mean of 11 micrograms per deciliter. (The Centers for Disease Control and Prevention places the action level at 5 micrograms per deciliter, but no level of lead is safe for children.) However, these numbers are based only on a simple blood sample collected when participants were 11 years old. In an ideal scenario, samples would’ve been taken when they were younger, throughout their childhood, and even through adulthood. 

Nevertheless, after controlling for some factors that may affect mental health, including childhood family socioeconomic status, maternal IQ, and family history of mental illness, the study found that every 5 micrograms per deciliter increase in blood lead levels was associated with a 1.34 point increase in general psychopathology, which includes all the mental health symptoms the team examined.

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This is a modest impact. The impacts of, say, childhood maltreatment or family history, can be far more severe. That doesn’t make this any less worth highlighting, though, said Joseph Braun, an associate epidemiology professor at Brown University who wasn’t involved in the study.

Higher blood lead levels at age 11 are linked to an increase in symptoms of psychopathology and difficult personality traits by age 38.
Image: Adapted from JAMA Psychiatry, 2019;76(4):1-9.

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“It’s important to note that lead is an exposure relatively easy to change,” he told Earther. “These are modest effects. They’re not making people fall over dead, but they are having an effect on people, and when you consider at the population level that more people are having a diagnosis of certain clinical disorders, that’s really important.”

Luckily, the blood lead levels of today are typically nowhere near what we saw in this study. Back then, the health impacts of lead weren’t as understood and the metal was found in our gasoline and paint.

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Increased risk of mental illness is just one of many ways childhood lead exposure can potentially impact a person’s life forever. Other studies have drawn links between lead exposure and decreased IQs or behavioral issues, including violence. Unfortunately, there’s still no real treatment for kids dealing with lead, said Mary Jean Brown who led the CDC’s Lead Poisoning Prevention Branch before going on to teach at the Harvard T.H. Chan School of Public Health. Prevention is key.

She’s not surprised at all with these findings and welcomes this as “a new area of research and another nail in the coffin of lead exposure,” she told Earther. This paper is just another reminder of why no person should be exposed to lead. There’s still much we don’t know about what it does to our bodies, but what we do know is pretty dark.

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