Alcohol, intelligence and violent crime in young males.

Research has demonstrated a relationship between alcohol and violent behavior, but proof of a causal connection remains elusive. A recent review concluded that the key task that remained was to identify sub-groups of the population for which alcohol promotes violence. Because alcohol might induce violence by causing cognitive disruption (e.g., misunderstood communication), less intelligent persons could be vulnerable because they start out closer to the lower limit of comprehension. Our objective is to investigate the effect of lower intelligence on the alcohol/violence relationship. This analysis uses data from the Buffalo Longitudinal Study of Young Men to investigate this hypothesis. Males, 16 to 19 years of age (N = 596), were selected from Buffalo, NY, by random digit dialing. High-risk males were oversampled. Two interviews were conducted 18 months apart, including drinking, criminal offenses, and psychological traits. Verbal intelligence was measured by the Ammons Quick Test and visual-motor intelligence by the Trail Making Test. An analysis of covariance was conducted with wave 2 average alcohol consumption and both measures of intelligence as independent variables, violent offending as the dependent variable, and race, wave 1 alcohol and wave 1 violence as covariates. Results show a positive main effect of wave 2 alcohol consumption, but also interactions with both verbal and visual-motor intelligence. These interactions indicate that the prevalence of violence increases significantly at low intelligence and high alcohol consumption levels. A parallel analysis with nonviolent offending as the dependent variable failed to find significant interactions. The combination of heavy drinking and lower intelligence is associated with a synergistic surge of violent behavior.