Suddenly it all makes sense...

Though cannabis can provoke psychotic symptoms, these effects appear to be caused chiefly by one of its components; and another compound that damps down its effects has potential as a medicine, scientists said.

The findings, to be announced at a conference that opens in London today, offer a possible explanation for anecdotal reports of increasing cases of psychosis and schizophrenia triggered by the drug.

As concentrations of tetra-hydracannabinol (THC), the main psychoactive element that can provoke psychosis, have risen, levels of the beneficial chemical, cannabidiol (CBD) have fallen. This could mean that users are being exposed to higher doses of the damaging chemical, while receiving less CBD, which tends to balance THC’s effects.

“There is a possibility that there are good guys and bad guys in cannabis,” said Markus Leweke, of the University of Cologne.

“THC is the bad guy, but there is a small body of literature that suggests CBD may prevent the induction of psychotic symptoms. Our study supports that view.”