Dope-smoking teens 'addicted by early 20s'

About one fifth of teenagers who smoke cannabis become dependent on the drug by early adulthood, but the addiction appears to be mental rather than physical, according to new research.

About one fifth of teenagers who smoke cannabis become dependent on the drug by early adulthood, but the addiction appears to be mental rather than physical, according to new research.

The study by Australian researchers found that the strongest factor in whether someone became dependent was frequency of use: one in three adolescents who smoked cannabis every week were hooked by their early 20s.

Writing in the British Journal of Psychiatry, the team from the Centre for Adolescent Health in Melbourne, Australia, said the findings suggested "the case for a more concerted public health response seems strong".

The research looked at cannabis dependence among 1,601 young adults aged 20 or 21. Most using cannabis had begun in their mid-teens, and almost 20 per cent of those were found to be dependent by the time they were young adults. Studies have shown that the strength of cannabis has increased tenfold since the 1960s.