BRITAIN'S brightest teenagers are among those most at risk of mental illness caused by smoking a potent form of cannabis, a leading expert has warned.

Professor Sir Robin Murray said it tended to be 'clever and sociable' youngsters who were damaged by using the super-strong strain of the drug, known as skunk.

Sir Robin, the foremost authority in Britain on the effects of smoking cannabis, led a landmark study with colleagues at the Institute of Psychiatry which found that regularly smoking skunk triples the risk of psychosis, as revealed last week by The Mail on Sunday.

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