New research has reopened the question of the harm caused by cannabis. A study in a journal published by the American Medical Association suggests 60,000 cases of depression in the UK could be caused by teenage use of marijuana.
This reinforces The Independent’s unfashionable caution about legalising soft drugs. While we welcomed Sajid Javid’s decision as home secretary to review the law on the medical use of cannabis, we warned about its association with mental illness. We argued that more research is needed before Britain presses ahead with the wider legalisation of the drug.
Today’s study is suggestive rather than conclusive. It finds that smoking cannabis before the age of 18 is associated with an increased risk of depression and suicide in adulthood. It is hard to be sure about cause and effect, however. It may be that teenagers prone to depression are more likely to try