November 10, 2008
Two Genes Influence Impulsiveness

Variants of genes for 5-HTT and BDNF appear to influence impulsivity, risk of alcoholism, and size of the brain's right orbitofrontal cortex (OFC).

PITTSBURGH, Nov. 6 A new study suggests that genetic factors influence size variations in a certain region of the brain, which could in turn be partly responsible for increased susceptibility to alcohol dependence.

It appears that the size of the right orbitofrontal cortex (OFC), an area of the brain that is involved in regulating emotional processing and impulsive behavior, is smaller in teenagers and young adults who have several relatives that are alcohol dependent, according to a study led by Dr. Shirley Hill, Ph.D., professor of psychiatry, University of Pittsburgh School of Medicine.

In the research, which was published this week in the early online version of Biological Psychiatry, Dr. Hill and her team imaged the brains of 107 teens and young adults using magnetic resonance imaging. They also examined variation in certain genes of the participants and administered a well-validated questionnaire to measure the youngsters' tendency to be impulsive.

The participants included 63 individuals who were selected for the study because they had multiple alcohol-dependent family members, suggesting a genetic predisposition, and 44 who had no close relatives dependent on drugs or alcohol. Those with several alcohol-dependent relatives were more likely to have reduced volume of the OFC.

When the investigators looked at two genes, 5-HTT and BDNF, they found certain variants that led to a reduction in white matter volume in the OFC, and that in turn was associated with greater impulsivity.

The 5-HTT is a transporter gene for the neurotransmitter serotonin. The gene has been linked to depression, hyperactivity, and disruptive behavior in boys. Low levels of BDNF, or Brain-derived neurotrophic factor, have been linked to assorted problematic cognitive phenomena as well. So a role for these genes in influencing the degree of impulsivity is plausible.

If you pride yourself in your self-control don't feel too smug about the wisdom of your free will in choosing to be so controlled. You probably just have a large right orbitofrontal cortex due to getting genes that code for a large right OFC.

Share |      Randall Parker, 2008 November 10 10:07 PM  Brain Addiction

Vince said at November 11, 2008 11:45 PM:

And we still have the ability to fight our impulsive behavior. So we're back where we started.

mark baard said at November 13, 2008 3:19 AM:

Or stuff ourselves with SSRIs? Which makes more-and-more sense. The pill to cure alcoholism, which Bill Wilson looked forward to, is coming.., Great find, thanks, Randall!

Shannon Love said at November 13, 2008 8:07 AM:

I don't think that "impulsive" neurological wiring is a disorder per se but rather represents just one of several behavioral strategies that our genes can create as they are reshuffled each generation. It's long been known that people with ADD, Touretts and other impulse control disorders respond much more quickly to unexpected stimuli than do individuals without the conditions. Under primitive conditions, having a few individuals in every group who could respond quickly to the unexpected could have paid off. After all, it is really only in the last few thousand years where people have had focus on a single task for hours on end or have had to make plans stretching years into the future. Further, people used to live and work in close teams in which individual decision making played a smaller role in long term plans. In such an environment, the decisions of slower reacting people would mitigate the harm caused by impulsive members but the group as a whole would have benefited from their quick decisions when it counted.

I think we will find that all of us have several genetically hardwired behavioral "settings" that provide advantages in some circumstances and disadvantages in others. Some of these behaviors will be a good fit for the modern world and others will not.

Lono said at November 18, 2008 9:51 AM:

Yes - well - I may not be the BEST engineer in he world - but come the Zombie Apocalypse - you'll be beggin' for me to hang around!

Wait... what was that Noise!??

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