Genes influence impulsive behavior, preceding the development of alcoholism

April 22, 2009

Numerous studies have shown that highly impulsive behavior - defined as the tendency to choose small, immediate rewards over larger, delayed rewards - is more prevalent in drug addicts and alcoholics compared to individuals without addictions. A new study using mice has found that genes influence impulsivity, which may then contribute to the risk for developing alcoholism.

Results will be published in the July issue of Alcoholism: Clinical & Experimental Research and are currently available at Early View.

"There is increasing evidence that the character trait of impulsivity predisposes towards addiction in all its forms, such as drugs, , gambling," said Nicholas J. Grahame, associate professor of psychology at Indiana University-Purdue University at Indianapolis. "Data from the National Epidemiologic Survey on Alcoholism and Related Conditions suggest that a variety of disorders that increase impulsivity - from bipolar disorder, to conduct disorder, and antisocial personality disorder (ASPD) - are associated with an increase in risk for alcoholism."

"The relationship between high impulsivity and drug use raises many questions," added Suzanne H. Mitchell, associate professor in behavioral neuroscience at Oregon Health & Science University. "For example, is an impulsive individual more likely to experiment with drugs, and then develop a problem? If such a relationship was found, identifying children or adolescents with high levels of impulsivity might, in theory, allow us to identify individuals at risk for developing a substance-use disorder like alcoholism."

Grahame and his colleagues tested several selected lines of alcohol-naďve : offspring of High Preferring (HAP) mice, HAP1 and HAP2; offspring of Low Alcohol Preferring (LAP) mice, LAP2; as well as offspring of low-drinking progenitor (HS/Ibg) mice. All of the mice were tested on a delay-discounting task, which employs two levers to provide subjects with a choice between a small, immediate or a large, delayed saccharin reward.

"We first used selective breeding to obtain mice genetically predisposed to drink alcohol," said Grahame. "The experiment was to create lines of animals that differ in genes related to alcohol drinking, and the central question was: 'Are any of the genes affected by this manipulation related to impulsivity?' To study this, we used a task that is widely used in both human and animal studies, which was to give a choice between an immediate but small reward and a delayed but large reward. The mice that had the genes to drink, the HAP1 and HAP2 mice, were more impulsive than their low-drinking counterparts, the LAP2 and HS/IBG mice."

"Given that these differences in impulsivity were present in alcohol-naďve animals," added Mitchell, "neural changes brought about by alcohol consumption could not be responsible for the differences between the two groups of mice."

"I think these data can clearly be extrapolated to humans," said Grahame, "because the same task can be used in a variety of species, including humans, to assess ability to plan for the future. The data suggest that if humans are like mice, their differences in impulsive behavior may also be affected by their genes, and these differences in impulsivity could confer some of the familial risk for alcoholism that we already know about."

Mitchell agreed. "The results imply that a subset of individuals who are 'family-history-positive' for alcoholism behave more impulsively," she said. "However, the results do not mean that individuals with high levels of impulsivity are doomed to a life of substance use, just as having genes associated with alcoholism does not destine you for a life of alcoholism. The interaction between genes and environment is critical. However, the study supports other work indicating that there is a genetic component to impulsivity. Future work could shed light on which genes are important in impulsive decision making, and which are shared with the propensity to develop a substance-use disorder."

"I think that the quality of impulsivity we are assessing here resonates with many folk stories about "fools" and their poor decision making," said Grahame. "I think of Jack of beanstalk fame who trades his cow for three magic beans, the grasshopper who has fun now while the ant plans for the future, and the pig that works hard to build the brick house that can survive the wolf. We try to inculcate low impulsivity in our children, because it is such an important survival trait for many reasons."

While the natural impulsivity of children tends to diminish as they mature, added Grahame, a decrease in heavy drinking that occurs for many during their teen years may be absent for those who have other problems, causing them to remain impulsive well into their adult years.

"Our data suggest that impulsivity contributes to high alcohol drinking and, consequently, the diagnosis of any disorder associated with life-long impulsivity - for example, ASPD, bipolar disorder, borderline personality disorder, and attention-deficit disorder - is grounds for serious concern about later problems with alcoholism and drug abuse, which can aggravate the severity of the disorders I just mentioned," said Grahame. "We already know this from human studies, but I think that the mouse data make us more certain about the causal direction, and genetic mediation, of some of these associations."

Source: Alcoholism: Clinical & Experimental Research

Explore further: Study links smoking and drinking

Related Stories

Study links smoking and drinking

December 23, 2005

A University of North Carolina study suggests chromosome regions containing genes related to alcohol addiction affect drinking behavior in smokers.

Researchers identify alcoholism subtypes

June 28, 2007

Analyses of a national sample of individuals with alcohol dependence (alcoholism) reveal five distinct subtypes of the disease, according to a new study by scientists at the National Institute on Alcohol Abuse and Alcoholism ...

Scientists identify gene that influences alcohol consumption

December 5, 2007

A variant of a gene involved in communication among brain cells has a direct influence on alcohol consumption in mice, according to a new study by scientists supported by the National Institute on Alcohol Abuse and Alcoholism ...

Recommended for you

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

Machine Translates Thoughts into Speech in Real Time

December 21, 2009

( -- By implanting an electrode into the brain of a person with locked-in syndrome, scientists have demonstrated how to wirelessly transmit neural signals to a speech synthesizer. The "thought-to-speech" process ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.