Environmental factors are important in determining whether teens experiment with alcohol or other drugs, but genetics plays a greater role in whether users become addicted, Science Daily reported March 19.

Researcher Marianne van den Bree of the Cardiff University School of Medicine and colleagues drew their conclusions from a study of twins. They found that while starting smoking cigarettes or using marijuana was associated with progression to harder drug use, there was not as strong an association involving alcohol use.

"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," said van den Bree. "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," she added. "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."

The research was published in the March 2007 issue of the journal Addiction.