High lead levels in early years up risk for later criminality

High lead levels before birth or in early childhood are a strong risk factor for adult criminal behavior, according to new findings from a large-scale study. The research is the first to directly measure blood lead levels during prenatal development and childhood and correlate these levels with arrest records in early adulthood.

The new study, by John Paul Wright and colleagues, is part of a long-term collaborative study on the effects of lead. Between 1979 and 1984, researchers recruited pregnant women living in lower-income Cincinnati neighborhoods with high concentrations of lead-contaminated housing. The researchers tested the mothers’ blood levels before the children’s birth and then tested the children’s blood lead levels at regular intervals through age 6. At the time of the follow-up, Wright and colleagues identified 250 of the 376 children from the initial study and determined the number of times these individuals (who were between the ages of 19 and 24 at follow-up) were arrested after they turned 18.

The researchers identified a total of 800 arrests in the group, with about 55 percent of subjects having at least one arrest. Higher blood lead levels before birth and at six years of age were associated with a greater number of adult arrests, and high childhood blood lead levels correlated with violent crime. For every 5 micrograms-per-deciliter increase in blood lead levels at six years of age, the risk of being arrested for a violent crime rose by nearly 50 percent.

The researchers note that neurological and behavioral consequences of lead exposure include reduced IQ, poor tolerance for frustration, hyperactivity, attention deficits, and weaknesses in executive control (higher brain functions including planning and impulse control). All of these, they point out, “are potent predictors of delinquent and criminal behaviors.”

The researchers say several mechanisms could explain the link between higher lead levels and increased risk for criminality. “Lead interferes with synapse formation, disrupts dopamine systems, and lowers serotonin levels,” they note. “Lead exposure has been shown to reduce MAOA (monoamine oxidase A) activity, and low MAOA activity has been associated with violent and criminal behaviors. One consequence of these alterations could be neural dysfunction in areas of the brain involved in arousal, emotion, judgment, and behavioral inhibition such as the prefrontal cortex.”

Commenting on the study, David Bellinger of Harvard says that even if high lead exposure contributes in only a small way to criminality, the finding is important because “in contrast to most other known risk factors for criminality, we know full well how to prevent it.” He adds that reduced IQ “is clearly only the tip of the iceberg” when it comes to the damaging effects of high lead levels in childhood.

The findings of the new study are consistent with earlier research by Herbert Needleman and colleagues, whose data strongly linked elevated lead levels to a heightened risk for delinquency One study by Needleman et al. evaluated 216 delinquents and 201 non-delinquents and found that convicted juveniles were nearly twice as likely as control subjects to have high bone lead levels (see related article, Crime Times, 2000, Vol. 6, No. 3, Page 4).

Commenting on the new study’s findings, Wright says, “I did not expect we would see an effect, much less a substantive effect and even less likely a highly resilient effect. The fact that we are able to detect the effects from childhood exposures now into adulthood stands as a testament to lead’s power to influence behavior over a long period of time.”