A multinational research team led by scientists at the National Institutes of Health has found that a genetic variant of a brain receptor molecule may contribute to violently impulsive behavior when people who carry it are under the influence of alcohol. A report of the findings, which include human genetic analyses and gene knockout studies in animals, appears in the Dec. 23 issue of Nature.
"Impulsivity, or action without foresight, is a factor in many pathological behaviors including suicide, aggression, and addiction," explains senior author David Goldman, M.D., 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."
In collaboration with researchers in Finland and France, Dr. Goldman and colleagues studied a sample of violent criminal offenders in Finland. The hallmark of the violent crimes committed by individuals in the study sample was that they were spontaneous 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 researchers sequenced DNA of the impulsive subjects and compared those sequences with DNA from an equal number of non-impulsive Finnish control subjects. They found that a single DNA change that blocks a gene known as HTR2B was predictive of highly impulsive behavior. HTR2B encodes one type of serotonin receptor in the brain. Serotonin is a neurotransmitter known to influence many behaviors, including impulsivity.
"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."