The monoamine oxidase A (MAOA) gene is an outer membrane mitochondrial enzyme that breaks down monoamines such as serotonin, noradrenalin and dopamine. A common polymorphism in MAOA results in high- or low-activity MAOA, and both genotypes have been linked to aggression and violence.
A Finnish study has found that drinking and high-activity MAOA can predict the risk of impulsive violence. This effect appears to diminish with age – which may partly explain why younger people are more likely to get into alcohol fuelled fights than older ones.
“Habitually violent-impulsive offenders are often expected to ‘grow out of their difficulties’ with increasing age. Surprisingly little accurate information, however, is available on this aging-impulsive aggression issue," says Roope Tikkanen, a researcher in the department of psychiatry at Helsinki University Central Hospital.
Tikkanen and his colleagues decided to look at the MAOA gene, alcohol consumption and aging as predictors for recidivism in impulsive violent behaviour among a sample of 174 Finnish alcoholic male offenders with histories of violence.
"Increased alcohol consumption and aging seem to predict violence – although these risk factors 'work' in opposite directions, and only concern individuals who have been given by nature a high-activity variant of MAOA”, Tikkanen says.
He hypothesizes that high-activity MAOA offenders may be helped to control their violent behaviors by coaching to maintain alcohol abstinence, and possibly by psychopharmacological treatment to increase central serotonin levels.
However, Tikkanen cautioned against genetic testing for individuals who may be worried for one reason or another about their risk. "Even though whole genome scans will one day be affordable, the average person probably has very many factors that differ from the violent offenders in the study. For instance, the average Finnish consumption is 10 kg pure alcohol per year, whereas the upper 10 percent of violent offenders drink around 100 kg pure alcohol a year."