CINCINNATI -- Could exposure to lead in early childhood be behind the rising levels of crime and other antisocial behaviors during the last half of the 20th century?
The first comprehensive lead study to track children over a period of time found that both prenatal and postnatal exposure to lead were associated with antisocial behavior in children and adolescents.
Researchers at the Children's Environmental Health Center at Cincinnati Children's Hospital Medical Center, in collaboration with University of Cincinnati researchers, followed inner-city adolescents recruited prenatally into the study between 1979 and 1985. Mothers known to be addicted to drugs or alcohol, diabetic, or those with proven neurological disorders, psychoses or mental retardation were excluded from the study.
Between 1997 and 1999, 195 of these adolescents received follow-up exams. Ninety-two percent were African American and 53 percent were male. Blood lead levels were taken from mothers during pregnancy and from children every three months between birth and age 6, covering the time period when most developmental growth involving the brain occurs.
Researchers asked the adolescents and their parents or legal guardians to document antisocial or delinquent behavior. This method of self-reporting has been proved to be more valid than official records, which reflect only a small portion of antisocial acts actually committed.
"Self-reported acts of delinquent behavior were common," says Kim Dietrich, Ph.D., associate director of Cincinnati Children's Environmental Health Center and the lead author of the Cincinnati Children's study. "Adolescents with the highest blood lead concentrations when they were first graders reported, on average, 4.5 more delinquent acts in the previous 12 months compared to children with the lowest blood lead concentrations as first graders. It appears that the neurodevelopmental effects of this avoidable environmental diseases of childhood may not be limited to declines in IQ or academic abilities."
Delinquency was defined as behaviors in violation of legal statutes involving some risk of arrest, including offenses against property or persons, or other illegal activities such as driving without a license and disorderly conduct.
The researchers found that exposure to lead was associated with antisocial behavior, even after adjusting for other factors that could lead to similar behavior. These included quality of home environment, low birth weight, parental intelligence and social class.
Surprisingly, the researchers found no gender differences in antisocial behavior. Girls were just as likely as boys to be violent and to be institutionalized for their behavior.
While lead could be interfering with the usual gender differences seen in behavior, it's more likely that gender is becoming less a predictor of behavior in inner-city populations, according to Dr. Dietrich, professor of Environmental Health and Pediatrics at the University of Cincinnati.
The study is published in Neurotoxicology and Teratology.