Half of young people using cannabis suffer side effects such as paranoia and blackouts, a UK survey suggests.
More than 80% of the 727 young people in their teens and early 20s polled by YoungMinds had tried the drug - the vast majority before they were 18.
The charity is calling for urgent research on the effects of cannabis on the developing teenage brain.
It is releasing guidance for young people and professionals on the effects cannabis may have on mental health.
-- BBC News