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A Genetic Clue To Adolescent Alcohol Use

In most Western societies, alcohol use is widespread among adolescents and young adults. In the U.S., the average adolescent drinks his first alcoholic beverage at the age of 13. Typically, alcohol use increases during adolescence and young adulthood but stabilizes or decreases at the age of approximately 25.  Family, twin and adoption studies suggest that there are genetic risk factors for alcoholism.  Different versions of a gene are called alleles and different alleles have different effects. Serotonin or 5-hydroxytryptamine (5-HT) is a neurotransmitter found in the central nervous system of humans and animals. It is a well-known contributor to feelings of well-being and contributes to many physiological functions. The 5-HT system has been one of the key targets in examining the genetic bases for alcohol use and dependence.  Although the exact role of 5-HT in alcohol use and abuse remains unclear, evidence exists that 5-HT deficits in the brain result in alcohol-seeking behavior in humans and animals.  5-HT availability in the brain is influenced by the serotonin transporter (5-HTT). A polymorphism (5-HTTLPR) located in a region of 5-HTT  has been a prime candidate for genetic association studies on alcohol abuse risk. (Polymorphism in nature simply means something exists in different forms.)
Scientists at Radboud University in the Netherlands examined the association between the 5-HTTLPR and the progression of alcohol use throughout adolescence and young adulthood. Non-regular drinkers (n=202) were selected from a Dutch nationwide sample of adolescents (mean age 13.4). Initially the presence or absence of the 5-HTTLPR polymorphism was determined by standard genotyping analysis. The participant’s alcohol use was then assessed annually across five years by means of self-reported responses to four questions: ‘How many alcoholic drinks did you consume in the past week at home on weekdays?’, ‘How many alcoholic drinks did you consume in the past week at home during the weekend?’, ‘How many alcoholic drinks did you consume in the past week when you were out on weekdays?’, and ‘How many alcoholic drinks did you consume in the past week when you were out during the weekend?’. Asking about these four specific situations forces respondents to actively ‘search’ their memory, which is supposed to increase the reliability of their response. The four answers equaled the amount of alcohol consumed in the past week. This method has been used frequently and reliably in other studies.
The 5-HTTLPR “short” allele was observed to predict an adolescent’s progressive use of alcohol use over time.  Adolescents with the 5-HTTLPR short allele showed a larger increase in alcohol consumption than those without the 5-HTTLPR short allele. This first multi-wave longitudinal study adds further insight into the role of genetic determination of adolescent alcohol use.

(van der Zwaluw, CS, Engels, RCME, Vermulst, AA, Rose, RRJ, Verkes, RJ, Buitelaar, J, Franke, B, Scholte, RHJ,: A serotonin transporter polymorphism (5-HTTLPR) predicts the development of adolescent alcohol use. Drug and Alcohol Dependence, epub (July 1, 2010) doi:10.1016/j.drugalcdep.2010.06.001

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