Teens who use marijuana may be at greater risk of permanent brain damage later in life, a study has revealed. About 18 million Americans report using marijuana daily or nearly every day, and use is on the rise, largely due to recent decriminalisation across the US. From 1992 to 2022, for example, daily and near-daily use saw a 15-fold increase. About one in seven of those users are teenagers, whose brains are still undergoing rapid changes in areas responsible for judgement, decision-making and memory. Now, the largest-ever study of American teenagers has found regular cannabis use restricted vital growth in...