Genetic Link To Heavy Substance Abuse In Teenagers

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 to try and identify the role played by genetic and environmental factors in whether teenagers experiment with substances and whether they go on to heavier substance use.

The study, published in the international journal Addiction found 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 study found 86 per cent of youngsters had drunk alcohol at some point in their lives and 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.

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, Cardiff University 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.