Young age at first drink may affect genes and risk for alcoholism

A team of researchers, led by scientists at Washington University School of Medicine in St. Louis, studied 6,257 adult twins from Australia. They wanted to learn whether twins who start drinking at an early age are more likely to develop a more heritable form of alcohol dependence than those who begin drinking later in life. The researchers found that the younger an individual was at first drink, the greater the risk for alcohol dependence and the more prominent the role played by genetic factors.

"There seemed to be a greater genetic influence in those who took their first full drink at a younger age," says first author Arpana Agrawal, Ph.D. "That's very consistent with what has been predicted in the literature and in the classification of types of alcohol dependence, but we present a unique test of the hypothesis."

Agrawal and her colleagues examined previously collected data from identical and fraternal, male and female twins, using statistical methods to measure the extent to which age at first drink changed the role of heritable influences on symptoms of alcohol dependence. Using the twin model, they were able to tease out genetic influences, shared environmental influences and non-shared environmental factors.

Agrawal's team found that when twins started drinking early, genetic factors contributed greatly to risk for alcohol dependence, at rates as high as 90 percent in the youngest drinkers. For those who started drinking at older ages, genes explained much less, and environmental factors that make twins different from each other, such as unique life events, gained prominence.

The twins in the study were 24 to 36 years old when they were interviewed, but some reported taking their first drink as young as age 5 or 6. The researchers found that those who were 15 or younger when they started drinking tended to have a greater genetic risk for alcohol dependence. Some who were 16 or older before they took their first drink later became alcohol dependent, but their dependence was related more to environmental factors.

(Edit:Ruby)