Disruption to gene HTR2B could affect decision-making and self-control and may explain why some people are more prone to impulsive behaviour

A genetic mutation that makes people more impulsive when they consume alcohol may explain why some are more prone to drink driving, impulsive sex and random acts of violence.

The mutation disrupts a gene called HTR2B which the body uses to make serotonin receptors in parts of the brain that have a governing role in decision making and self-control.



The genetic glitch has only been found in Finland so far, where 2.2% of the genetically isolated population carry the mutation, amounting to more than 100,000 people.

A study in 2010 was the first to identify the mutation in Finns, though many of the subjects who donated DNA were violent offenders with alcohol problems and personality disorders, making it hard to assess its effects in the general population.



Roope Tikkanen, a psychiatrist at the University of Helsinki, gathered information on impulsive behaviour from a small group of 14 people who carried the mutation and 156 controls who did not. None were violent offenders. He found that when compared to controls, the carriers had more aggressive outbursts, got into fights, and behaved in a more impulsive manner when under the influence of alcohol.



The carriers were not alcoholics as measured by their consumption, but had a tendency to lose control when they had a few drinks, he writes in the journal Translational Psychiatry.



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“We wanted to take a look at healthy people in the general population to check if this mutation had any effects. The most interesting finding was that it caused impulsive behaviour while under intoxication, and that included impulsive sex, impulsively spending money, and driving under the influence,” Tikkanen told the Guardian.



“When they are sober they have a tendency towards impulsivity, but our discovery is that it will be enhanced by small amounts of alcohol,” he said.



The study is too small to draw firm conclusions, and many of the people who took part were relatives of offenders who took part in the 2010 study, meaning their impulsive behaviour may be partly a product of the shared environment they grew up in. But if larger studies confirm the genetic link, Tikkanen said doctors in Finland may consider screening for the mutation to identify those at risk of impulsive acts that could land them in prison.



People who carry the mutation could be recommended to attend courses to help them keep their alcohol consumption within healthy limits, and have therapy to boost their self control, he said.



It is unclear how the mutation affects impulsive behaviour and why alcohol may exacerbate its effects. But further work on the mutation may go beyond elucidating the biological drivers of reckless behaviour and shed light on mental disorders driven by serotonin imbalances.



“The interesting thing about this is that it tells us something about the mechanism of the serotonin receptor globally. It’s like a laboratory experiment that you can’t usually do in humans,” Tikkanen said.