In 1987, a large-scale Swedish study confirmed an association between cannabis use and the development of schizophrenia. Ever since, it has become widely accepted by clinicians that there are links between cannabis use and mental illness. Experts have expressed particular concern about the mental-health effects of cannabis use on young people, as ‘adolescence is the developmental stage when drug-using patterns emerge and teenagers may be more vulnerable than adults to the effects of cannabis’.

However, the research to date suggests that the relationship is complex—for example, there is ongoing debate about causality, as well as over the role of other factors in the development of mental illness among cannabis users.

This research note provides an overview of recent research into the links between cannabis use and mental-health problems.