Exposure to lead via car exhaust in the first five years of life may be responsible for an estimated 151 million excess mental disorders in the United States, according to a study in the Journal of Child Psychology and Psychiatry.
Michael J. McFarland, Ph.D., and colleagues at the University of Florida used data from the National Health and Nutrition Examination Surveys (NHANES) and historic data on leaded-gasoline consumption to estimate early life blood-lead levels from 1940 to 2015. McFarland and colleagues then calculated general psychopathology points (or p-factor points), gained by the U.S. population based on the level of early-life exposure. P-factor points roughly equate mental illness risk in that every three points gained by an individual above a certain threshold will result in one new psychiatric diagnosis. In addition to general psychopathology, the researchers calculated points for three behavioral subdomains known to be adversely affected by lead exposure: internalizing symptoms, attention-deficit/hyperactivity disorder (ADHD) symptoms, and the personality traits of neuroticism and conscientiousness.
Assuming that published lead-psychopathology associations are causal and not purely correlational, the researchers found that by 2015 the U.S. population had gained 602 million general psychopathology points as a result of childhood lead exposure. This equates to around 1.9 points per person, and potentially 151 million excess mental disorders. By 2015, the U.S. population had also:
- Gained 202 million internalizing symptom-points
- Gained 135 million ADHD symptom-points
- Gained 45 million neuroticism points
- Lost 63 million conscientiousness points
The association between lead exposure and mental illness was most pronounced in individuals born between 1966 and 1986, most of whom belong to Generation X and were children during the peak use of leaded gasoline.
“Large swaths of the population likely experienced elevated lead-linked mental illness symptomatology and altered personality, with significant implications for national well-being, innovation, economic productivity, need for and use of psychiatric services, and the prevalence of physical comorbidities, all of which bear individual investigation and estimation,” the researchers wrote. “The contribution of legacy lead exposures to population health and disease may be much larger than previously assumed.”
For related information, see the Psychiatric News article “Mental Health Impact of Air Pollution in the Southeast Asian Subcontinent.”
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