Importance
Lead is a neurotoxin with well-documented effects on health. Research suggests lead may be associated with criminal behavior. This association is difficult to disentangle from low socioeconomic status, a factor in both lead exposure and offending.
Objective
To test the hypothesis that higher childhood blood-lead level (BLL) is associated with greater risk of (1) criminal conviction, (2) recidivism (repeat conviction), (3) violent conviction, and (4) variety of self-reported criminal offending, in a setting where BLL was not associated with low socioeconomic status (SES).
Design
Prospective cohort study based on a population-representative 1972–73 birth cohort; the Dunedin Multidisciplinary Health and Development Study observed participants to age 38 years.
Setting
Dunedin, New Zealand
Participants
553 lead-tested members of the Dunedin Study
Exposure
BLL measured at age 11 years.
Main Outcomes and Measures
Official criminal conviction cumulative to age 38 years (data collected in 2013). Single conviction or recidivism. Nonviolent or violent crime conviction. Self-reported variety of crime types at ages 15, 18, 21, 26, 32, and 38 years.
Results
Participants included 553 individuals who had been lead-tested at age 11 years (54% male). Mean (SD) BLL at age 11 years was 11.01 (4.62) μg/dL. Outcome prevalence was: criminal conviction, 28%; recidivism, 16%; violent conviction, 10%. Self-reported offending variety ranged from 0–10 at each assessment and followed the well-established age-crime curve. BLL was a poor predictor of criminal conviction (AUC .58).
Overall, associations between BLL and conviction outcomes were weak. Estimated effect of BLL was lower for recidivism than for single conviction and lower for violent offending than nonviolent offending. Sex-adjusted associations between BLL reached statistical significance for only one of the six self-reported offending outcomes, at age 15 years (r=0.10; 95%CI, 0.01, 0.18; P = .023).
Conclusions and Relevance
This study overcomes past limitations of studies of BLL and crime by studying the association in a place and time where the relation was not confounded by childhood socioeconomic status. Findings failed to support a dose-response association between BLL and consequential criminal offending.