Cannabis brain effects study struggles to attract black UK users

Exclusive: Fears findings will represent only white population if too few people of colour take part

A major study into the effects of cannabis on the human brain is at risk of being partially thwarted because too few black users have agreed to take part.

White people have come forward in large numbers offering to get involved in King's College London's 2.5m study of how the drug may contribute to paranoia and psychosis in some users but not others. It is hoped the project will pave the way for wider medicinal use and make illegal recreational use safer.