A cannabis-like substance produced by the brain may dampen delusional or psychotic experiences, rather than trigger them.
Heavy cannabis use has been linked to psychosis in the past, leading researchers to look for a connection between the brain's natural cannabinoid system and schizophrenia.
Sure enough, when Markus Leweke of the University of Cologne, Germany, and Andrea Giuffrida and Danielle Piomelli of the University of California, Irvine, looked at levels of the natural cannabis-like substance anandamide, they were higher in people with schizophrenia than in healthy controls.
Compared with 84 healthy volunteers, levels were six times as high in people with symptoms of psychosis and eight times as high in those with schizophrenia.
But were the high anandamide levels triggering the psychotic symptoms or a response to them? Leweke and his colleagues found, to their surprise, that the more severe people's schizophrenia was the lower their anandamide levels.
The team's theory is that rather than triggering psychosis, the substance is released in response to psychotic symptoms to help control them. People with the worst symptoms might be unable to produce sufficient anandamide to prevent them.