Smoking powerful "skunk" cannabis triples the risk of suffering a serious psychotic episode, scientists have found.

The drug is linked to one quarter of all new cases of psychosis, the study revealed.

The findings add to a compelling body of evidence that smoking strong cannabis "tilts the odds" towards a person developing psychosis, which leads to schizophrenia in about half of cases.

The study found that people who smoked skunk every day had five times the normal risk of experiencing extended episodes in which they heard voices, suffered delusions or demonstrated erratic behaviour.

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