My 'Warrior Gene' and My Propensity for Criminality

It's way too early to start putting people like me in jail based on our genomes


Abode of Chaos/Flickr

Researchers have been probing the human genome in search of genetic variants that might affect the propensity to violent and criminal behavior. Lots of studies have focused on versions of the monoamine oxidase A gene (MAOA). This gene produces an enzyme that controls the levels of various neurotransmitters such as dopamine and serotonin. I was intrigued by a recent study in which Finnish researchers report that low activity versions of MAOA are associated with violent criminal behavior and higher rates of recidivism. The researchers also found that interactions with versions of another gene CDH13 exacerbates criminal tendencies. In fact, the researchers calculated that "at least about 5-10% of all severe violent crime in Finland is attributable to the aforementioned MAOA and CDH13 genotypes."

The low and high activity versions of the MAOA gene are distinguished by a promoter region that can consist of repeats of a 30-base pair sequence that reduce or increase MAOA activity. Low activity results from having just 2 or 3 repeats, whereas high activity stems from 4 or 5 repeats of this sequence. The low activity version of MAOA has been nicknamed the "warrior" gene.

Some time back I deposited the raw results of my genotype screening tests from 23andMe at SNPedia where it is constantly updated by Promethease. I was curious to see what version of the MAOA gene I happen to have. It turns out that I very likely have the 3-repeat warrior variant. Hmm. My last fight was in 8th grade and I have so far avoided jail. The Finnish researchers also report that drinking alcohol heightens the risk that those affected with the low activity MAOA variants will behave violently. I do confess to occasionally raising my voice during arguments (usually over politics or architecture) fueled by alcohol, but none have ever come to fisticuffs.

So what about my CDH13 alleles? It turns out that I am homozygous for the protective version of that gene. So maybe that helps to explain my relatively placid nature.

Would widespread genotyping for these variants be useful; perhaps by applying some form of intervention to forestall violent acts by affected males? Medpage Today notes that Vanderbilt University forensic psychiatrist Stephen Montgomery thinks that "the relatively low population-attributable risk meant that there is no immediate practical application, since many individuals carrying the risk alleles identified in the study have no history of violence, and many violent individuals don't carry them." In other words, it's way too scientifically premature to start putting people like me in jail based on our genomes.

Go check out my Promethease results to see what else is wrong with me.

Via the invaluable Genetic Literacy Project.