Teenagers who adopt a daily cannabis habit before the age of 17 are 60 per cent less likely to finish secondary school or university, compared to peers who have not used the drug, researchers claim.
The study also found that regular teenage cannabis users are seven times more likely to attempt suicide and eight times much more likely to use other drugs.
Experts behind the Australian study hope that their research will be taken into account when considering whether it is a good idea to legalise the drug.
‘Our findings are particularly timely given that several US states and countries in Latin America have made moves to decriminalise or legalise cannabis, raising the possibility that the drug might become more accessible to young people,’ said Richard Mattick, professor of drug and alcohol studies at the University of New South Wales, Australia.
Cannabis is the most widely used illicit drug across the world and recent statistics have shown that adolescents in some countries are starting to smoke it at an increasingly young age, with some using the drug daily.
The study, published in The Lancet Psychiatry suggests that regular teenage cannabis users have an 18 times greater chance of becoming dependent on the drug in later life.
Researchers combined data on up to 3,765 participants who used cannabis from three large, long-running longitudinal studies to find out more about the link between the frequency of cannabis use before the age of 17 years and seven developmental outcomes up to the age of 30.
These outcomes included completing high school, obtaining a university degree, cannabis dependence, use of other illicit drugs, suicide attempt, depression, and welfare dependence.
They found clear links between frequency of cannabis use during adolescence and ‘young adult outcomes’ after taking into account factors such as sex, ethnicity and socioeconomic status.
According to the study’s lead author, Dr Edmund Silins, ‘Our results provide strong evidence that the prevention or delay of cannabis use is likely to have broad health and social benefits.