Genetic Variant + Alcohol May Trigger Impulsive, Violent Behavior
While under the influence of alcohol, certain people who have a genetic difference in a brain receptor molecule may be more prone to violent, impulsive behavior. The study, led by scientists at the National Institutes of Health, is found in the December issue of Nature.
“Impulsivity, or action without foresight, is a factor in many pathological behaviors including suicide, aggression, and addiction,” says David Goldman, M.D., senior author and chief of the Laboratory of Neurogenetics at the NIH’s National Institute on Alcohol Abuse and Alcoholism (NIAAA).
“But it is also a trait that can be of value if a quick decision must be made or in situations where risk-taking is favored.”
Goldman and a team of international colleagues analyzed a sample of violent criminal offenders in Finland; the strongest common factor among these crimes was spontaneity and purposeless.
“We conducted this study in Finland because of its unique population history and medical genetics,” says Dr. Goldman.
“Modern Finns are descended from a relatively small number of original settlers, which has reduced the genetic complexity of diseases in that country. Studying the genetics of violent criminal offenders within Finland increased our chances of finding genes that influence impulsive behavior.”
The scientists sequenced the criminals’ DNA and compared the results with DNA from a control group of non-impulsive Finnish individuals. They discovered that a certain DNA change that inhibits the gene HTR2B –which encodes one type of serotonin brain receptor –was predictive of strong impulsive tendencies.
“Interestingly, we found that the genetic variant alone was insufficient to cause people to act in such ways,” notes Dr. Goldman.
“Carriers of the HTR2B variant who had committed impulsive crimes were male, and all had become violent only while drunk from alcohol, which itself leads to behavioral disinhibition.”
“Discovery of a genetic variant which predicts impulsive behavior under certain conditions in one human population may have much wider implications,” says NIAAA Acting Director Kenneth R. Warren, Ph.D.
“The interaction with alcohol intoxication is interesting, as is the apparent involvement of a neurotransmitter pathway that has been regarded as important in addictions and other behavior.”
The scientists also discovered that when the equivalent HTR2B gene was knocked out or turned off in mice, the rodents also displayed more impulsivity. Studies that further include the alcohol factor in the knockout mice are being continued.
Finally, this research could lead to a greater understanding of certain impulsive behaviors and may pave the pathway for better diagnostic strategies and effective treatments. However, the researchers note that impulsivity is a complex trait with a variety of genetic and environmental triggers.
“Although relatively common in Finland, the genetic variant we identified in this study is unlikely to explain a large fraction of the overall variance in impulsive behaviors, as there are likely to be many pathways to impulsivity in its various manifestations,” says Dr. Goldman.
Source: National Institutes of Health