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Genetic link to heavy substance abuse in teenagers

08 March 2007

A team led by School of Medicine researchers has made important new discoveries about teenagers’ use of addictive substances.

The team found that family and community experiences play an important role in whether teenagers experiment with alcohol, cigarettes and marijuana, but genetic influences become more important for progression to heavy substance use.

Researchers questioned more than 1,200 pairs of identical and non-identical twins aged 11-19 in Wales and Manchester about their use of these substances.

The study, published in Addiction, the journal of the Society for the Study of Addiction, found 86 per cent of youngsters had drunk alcohol at some point in their lives. Of these, one third reported binge drinking, drunkenness, or getting into situations they later regretted because of alcohol. Cigarettes had been tried by 58 per cent, with 24 per cent reporting heavy use. Just 22 per cent reported trying marijuana and of these, 62 per cent had used it fewer than six times in their life.

There was a strong link between starting to smoke tobacco or marijuana and going on to heavy use. There was a weaker link for alcohol, suggesting that many teenagers may experiment with drink without developing a problem.

The researchers also found that family and community factors played a large part in whether a young person started using a substance, but genetic factors were more important in the progression to heavy use.

Lead researcher Dr Marianne van den Bree of the Department of Psychological Medicine, at Cardiff University’s School of Medicine said: "It makes sense that environmental factors such as family and peer influences, cost and availability play a more important part in whether a teenager experiments with these substances. However, biological processes in the brain and body may be more important in the progress towards addiction.

"The strong link between starting smoking and going on to heavier use suggests that public health strategies should concentrate on stopping teenagers from experimenting with cigarettes in the first place. By contrast, given the large numbers who try alcohol without developing a problem habit, it may be that drink strategies should focus on those at risk of heavy use. However, young people should still be warned against drinking too much, because of the risk of accidents and fights."

The study was conducted by researchers at Cardiff’s Department of Psychological Medicine; the Department of Psychiatry and Human Genetics, Virgina Commonwealth University, Richmond, Virginia, USA; and Oxfordshire Community Mental Healthcare Trust, Oxford.