A new study investigates the impact of lead exposure in childhood on later adult outcomes. The project, headed by Aaron Reuben in the Department of Psychology and Neuroscience at Duke University, looked into effects of childhood lead exposure on psychopathology, externalizing and internalizing disorder symptoms, and personality traits at multiple time points in participants’ childhood and early-adult lives.
There is no universal consensus regarding a threshold for safe levels of lead exposure, but abundant research has linked increased exposure in childhood to undesirable outcomes including poor academic achievement, compromised cognitive functioning, higher rates of problem behavior, and later life outcomes including psychiatric dysfunction and antisocial behavior. Research in this realm remains relevant due not only to implications for current adults but also to recent events such as the Flint, Michigan water crisis with new and potentially lasting consequences.
Although previous research had established the relationship between increased lead exposure in childhood and cognitive deficits and antisocial outcomes in adulthood, Reuben and team’s work published in JAMA Psychiatry extend these findings. Assessing participant functioning at multiple time points and considering adult personality traits in relation to childhood blood lead levels (BLLs) together reflect the team’s novel contributions.
Their results link lead exposure to greater psychopathology throughout adulthood, and the development of difficult personality traits. Because inattention, hyperactivity, and antisocial behavior have been connected to lead exposure in childhood in past research, but have been mostly unexplored in adult populations, this new work provides insights into the extent to which these challenges last and impact the lifespan.
“With this study, we undertook, to our knowledge, the longest and largest psychiatric follow-up to date in a cohort of adults who were lead exposed and lead tested as children, as well as the only follow-up to use (1) repeated clinical interviews assessing psychopathology symptoms across adulthood up to 38 years of age; (2) comprehensive, dimensional measures of psychopathology that account for severity, comorbidity, and reoccurrence; and (3) a broad measure of adult personality (Big Five Personality Inventory) that did not rely on self-report.”
The authors highlight that many adults who are now entering middle age were exposed to lead at extremely high rates on an international scale compared to youth today. This was particularly true in New Zealand, home to the participant sample used in Reuben and teams’ investigation, and is partially attributable to peak use of lead in gasoline in the 1970s. With regard to current perceptions of risk associated with lead exposure, the researchers explain that “from 1976 to 1980, the average child living in the United States had blood lead levels (BLLs) 3 times higher (>15 μg/dL)1 than the current reference value for clinical attention (5 μg/dL).”
Reuben and colleagues were able to use data from approximately 600 participants in the Dunedin Multidisciplinary Health and Development Study. This database provided rich data reflecting assessments performed at birth and 3, 5, 7, 9, 11, 13, 15, 18, 21, 26, and 32 years of age. Measures factored into the study included blood lead levels (BLLs), child externalizing and internalizing problems at the 11-year time point, assessment of symptoms of mental disorder, structure of psychopathology, and adult personality characteristics. They used regression techniques to assess the extent to which BLLs predicted mental health and personality features.
The study authors highlight three important findings:
- “Across nearly three decades of follow-up, childhood BLLs were associated with higher levels of general psychopathology, driven primarily by greater rates of internalizing and thought disorder symptoms.”
- “Childhood BLLs were associated with higher neuroticism, lower agreeableness, and lower conscientiousness.”
- “Childhood BLLs were associated with greater externalizing and internalizing symptoms assessed contemporaneously with BLL measurement at 11 years of age.”
Findings indicate that quality of life and interpersonal functioning are affected in domains not represented in research previously looking at lead exposure as a predictor of psychopathology. Behavioral health factors compromised in populations of children with disproportionately high BLLs (e.g., school performance, attention, flexibility, etc.) may transcend early life, and extend into adulthood impacting daily functioning and personality beyond standard measures of mental health.
Reuben, A., Schaefer, J. D., Moffitt, T. E., Broadbent, J., Harrington, H., Houts, R. M., . . . Caspi, A. (2019). Association of Childhood Lead Exposure With Adult Personality Traits and Lifelong Mental Health. JAMA Psychiatry. (Link)