Decades of Leaded Gasoline Tied to U.S. Mental Health Crisis

While we’ve known for years about the physical dangers of lead exposure, we’re still learning how bad it was for us mentally. Now, new research exposes the long-term psychological consequences of lead exposure – from gasoline in particular – on one wide swath of the U.S. population.

As if Generation X didn’t have it bad enough, researchers estimate that more than half of Americans suffered dangerous levels of lead exposure in their childhood. And that exposure resulted in profound effects on their mental health, personality traits, and well-being.

Leaded Gasoline’s Lethal Legacy

Gasoline exposed kids to lead nearly every day from the mid-20th century until 1996, when regulators phased it out. Between 1960 and 1990, lead exposure exceeded modern safety thresholds for at least 170 million Americans under the age of five. For about 60 million of those children, exposure levels were three to six times higher than what we know is hazardous now.

Earlier research has shown that lead exposure – especially early in life – poses a threat to brain development, hampering cognitive functions, motor skills, and emotional regulation.

This latest research illustrates how the consequences reach far past past individual health to influence population-wide mental health and personality trends.

An Influence on Mental Health and Personality?

The research quantifies the psychological burden of lead exposure, identifying a cumulative increase of 602 million general psychopathology points across the population. That’s equivalent to a 0.13 standard deviation rise in liability to mental illness, which corresponds to an estimated 151 million additional mental disorders, including heightened risks for anxiety, depression, and attention-deficit/hyperactivity disorder (ADHD). The population-level symptoms of internalizing disorders – such as  anxiety and depression – jumped by 0.64 standard deviations, while ADHD-related symptoms grew by 0.42 standard deviations.

In terms of personality traits, the research tied lead exposure to a 0.14 standard deviation increase in neuroticism, associated with negative emotionality, and a 0.20 standard deviation decrease in conscientiousness, reflecting less self-control and goal-oriented behavior.

The Lead-Crime Hypothesis

The consequences of lead exposure appear to be most striking among anyone born between 1966 and 1986 – Generation X – who endured peak lead levels growing up.

This paper suggests that this generation’s heightened vulnerability to mental illness and personality changes might have contributed to more far-reaching societal phenomena – such as increased demand for psychiatric care and juvenile delinquency – during their formative years.

This data backs up previous research that put forth a “Lead-Crime Hypothesis,” which linked falling crime rates in the 1990s and 2000s to less lead exposure. This theory suggests that lead abatement accounted for anywhere between a 7 percent and 28 percent of the drop in the U.S. homicide rate at the time.

Even though the last remaining countries stopped using leaded gasoline in 2021, other sources of exposure linger on. These include lead-based paints, industrial emissions, contaminated soil, and aging water infrastructure. Worldwide, an estimated 800 million children remain at risk of harmful lead exposure, particularly in underregulated areas of the world.

A Call for Action

This paper’s authors stress the need for continued vigilance and expanded lead screening, particularly for kids. They also argue for increased recognition of lead poisoning as a neurodevelopmental disorder within psychiatric diagnostic frameworks, which could pave the way for more resources for improved prevention and intervention efforts.

This research builds on prior findings that lead exposure cost the U.S. population more than 800 million IQ points, underscoring its pervasive effects on cognitive and psychological health. As a result, the authors insist on more research into the societal implications of lead exposure, including its impact on economic productivity, innovation, and public health systems.

In conclusion, the legacy of leaded gasoline – at least in the United States – represents a public health crisis with enduring side effects. The findings highlight the importance of addressing both historical and ongoing sources of lead exposure to mitigate its impact.

Further Reading

ADHD’s Fluctuating Nature Challenges What We Think We Know

Slower Traffic, Quieter Streets Improve Urban Life

CDC Report Reveals Jump in Adult Anxiety and Depression