In a discovery that could help scientists further understand impulsivity in humans, researchers announced that they found a genetic variant that may contribute to spontaneous violent behavior.
In a new study released in the journal Nature, a multinational research team examined the genes of 96 violent criminal offenders in Finland with behavioral disorders and compared it with DNA from a control group of 96 people in the country who had no such psychiatric diagnoses.
The offenders had been diagnosed with antisocial personality disorder, borderline personality disorder or intermittent explosive disorder, all conditions with symptoms of impulsive aggression.
The mutation was found to affect the brain's levels of serotonin, a neurotransmitter that affects mood, appetite, sleep and impulsive behavior.
"Impulsivity is a normal dimension of behavior, but it also plays a role in many psychiatric disorders, including alcoholism and suicidalism," said Dr. David Goldman, chief of the Laboratory of Neurogenetics at the National Institute on Alcohol Abuse and Alcoholism, in Bethesda, Md., and senior author of the study. "These disorders are often difficult to disentangle at the causal level, but by studying traits, we can find genes that contribute to important aspects of them."
Researchers specifically conducted the study in Finland because of its unique population and medical genetics. Goldman said modern Finns descend from a relatively small number of original settlers, which increased the chance of finding specific genes that influence impulsive behavior.
"Finns have the same degree of genetic diversity as people from other cultures, but their genetic disease diversity is reduced," said Goldman. "Genetic heterogeneity tends to be reduced in Finland because of its unique population, which was founded by two major waves of migration."
"There were two triggers in people with the genetic mutation: the male sex and alcohol," continued Goldman. "Everyone who carried this gene and committed a violent crime was intoxicated, and this is an important interactive factor to note."
Dr. Jason Jerry, a psychiatrist at the Alcohol and Drug Recovery Center at Cleveland Clinic, was struck by the overlap between serotonin levels, alcohol and impulsive behavior.
"This is important to look at because serotonin is one of the main neurotransmitters that have been looked at across the board, from alcoholism to suicide," said Jerry. "And in this study, it wasn't just the variant of the gene. The variant had to be coupled with intoxication."
But doctors note that violent and severely impulsive behavior is never cut and dry. The traits can be attributed to a host of nature and nurture characteristics, unique to each person.
Impulsivity is defined as action without foresight. It is the center point of many psychiatric behaviors including suicide, aggression and alcoholism. Other conditions that feature highly impulsive behavior include kleptomania, pyromania, intermittent explosive disorder and trichotillomania (the compulsion to pull one's own hair out).