A novel genetic mutation appears to be linked to impulsive and reckless behavior when under the influence of alcohol.
Researchers from the University of Helsinki, Finland, concentrated on the serotonin 2B receptor gene (HTR2B). This gene plays a central role in the transmission of serotonin around the brain.
A specific mutation of the gene called Q20 has previously been linked to impulsivity, which is connected to a number of mental health problems. About 2.2 percent of the population of Finland carry the mutation.
The team, led by Dr. Roope Tikkanen, undertook further analysis on carriers of the mutation and found a clear link to impulsive and reckless behavior when drunk, including impulsive sex, impulsively spending money, and driving under the influence. Details are published in the journal Translational Psychiatry.
The authors report, “HTR2B Q20 carriers demonstrated aggressive outbursts, got into fights and behaved in an impulsive manner under the influence of alcohol. They were also arrested for driving while under the influence of alcohol more often than the controls.
“The HTR2B Q20 carriers were not alcoholics per se, as measured by average alcohol consumption, and were not diagnosed as alcoholics, but they had a tendency to lose behavioral control while under the influence of alcohol.”
Tikkanen added, “The results also indicate that persons with this mutation are more impulsive by nature even when sober, but our discovery is that it will be enhanced by small amounts of alcohol.”
“The impact of one gene on complex phenomena is typically minor,” he said. “But it is possible to identify the impact of such a genetic mutation in the Finnish population, as our historical isolation has led to a relatively homogenous gene pool.”
The team hopes to test this association in larger clinical samples of individual patients who suffer greatly from problems with impulse control. If the link is confirmed, they say that preventive measures could be taken, such as advising susceptible people to decrease alcohol consumption or become abstinent.
If necessary, carriers of the gene could also be offered help to increase their control over impulsive behavior and emotions through cognitive psychotherapy, drug treatment, or psychosocial interventions.
Findings from the study will also help inform understanding of how the expression of this gene is affected by factors in the environment, and may help suggest targets for novel drug therapy.
While analyzing the results, the team found a high rate of “mood disorder symptoms and emotional dysregulation” among the HTR2B Q20 carriers. “This was surprising,” they write, “as the focus of our hypothesis was on impulsivity. However, impulsivity and emotional dysregulation are closely related phenomena.”
They add, “Though not fully consistent, a pattern matching that of a passive-dependent personality emerged. Personality features such as relatively low interest in novelty and exploratory activities, anxiety, fear of uncertainty and low persistence were characteristic of the HTR2B Q20 carriers.”
This is not unexpected, however, as the Q20 mutation is likely to interrupt serotonin production and transmission. A lack of serotonin movement around the brain has long been considered an important cause of depression, and also with “impulsive-aggressive behavior,” the team explains.
But they point out, “The acute effects of ethanol [alcohol] on neurotransmission (for example, dopamine release) and behavior may explain these results, in combination with the passive-dependent personality observed in the present study.” In other words, ethanol may augment an inherent tendency to impulsive decision-making, and then cause acute disinhibited behavior.
To sum up, they write, “Despite the fact that one gene rarely explains a large proportion of behaviors, these preliminary results suggest that the HTR2B Q20 may have a role in the inter-individual differences of behavior after exposure to alcohol.”
While the study is too small to draw firm conclusions, if larger studies confirm the genetic link, Tikkanen said doctors in Finland may consider screening for the mutation to identify those at risk.
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.
“The interesting thing about this is that it tells us something about the mechanism of the serotonin receptor globally,” Tikkanen said. “It’s like a laboratory experiment that you can’t usually do in humans.”
Tikkanen, R. et al. Impulsive alcohol-related risk-behavior and emotional dysregulation among individuals with a serotonin 2B receptor stop codon. Translational Psychiatry, 17 November 2015 doi: 10.1038/tp.2015.170