British scientists have discovered how a substance in cannabis called Cannabidiol, or CBD, acts in the brain to reduce abnormal activity in patients at risk of psychosis.

It's hoped that the substance could be used in a possible treatment for the condition because CBD is non-intoxicating, and cannot affect the user's judgement or behavior in the same way as drugs or alcohol.

King's College researchers lined up 33 young people experiencing signs of psychosis, although they they had not been shown to have the full-blown mental condition.  The subjects were treated with capsules of CBD.  Imagery of the brains of these young people revealed that taking CBD capsules reduced abnormal activity in three areas of the brain: the striatum, medial temporal cortex and midbrain.  Those are the same areas where abnormal activity has been linked to the development of psychotic disorders, such as schizophrenia.

CBD is less likely to cause harmful side effects than the current crop of drugs used to treat these disorders, such as weight gain and other health problems.

"One of the reasons CBD is exciting is because it is very well tolerated compared to the other anti-psychotics we have available," said King's College researcher Dr. Sagnik Bhattacharyya.  "There is an urgent need for a safe treatment for young people at risk of psychosis," he added.

The Institute of Psychiatry, Psychology and Neuroscience at King's College now plans a 300-patient clinical trial of CBD as a treatment for psychosis, with test subjects to be identified as early as next year.