Smoking potent cannabis was linked to 24% of new psychosis cases analysed in a study by King's College London.

The research suggests the risk of psychosis is three times higher for users of potent "skunk-like" cannabis than for non-users.

The study of 780 people was carried out by KCL's Institute of Psychiatry, Psychology and Neuroscience.

A Home Office spokesman said the report underlines the reasons why cannabis is illegal.

Sian Lloyd reports.