Pubdate: Sat, 29 May 1999 Source: New Scientist (UK) Page: 7 Copyright: New Scientist, RBI Limited 1999 Contact: letters@newscientist.com Website: http://www.newscientist.com/ Author: Jonathan Knight, San Francisco

ARE PEOPLE WITH SCHIZOPHRENIA DRAWN TO SMOKING POT?

A COMPOUND related to the active ingredient in marijuana may be accumulating in the spinal fluid of people with schizophrenia. This might explain why many sufferers smoke pot.

Many researchers blame schizophrenia on an overactive dopamine system in the brain. Daniele Piomelli and colleagues at the University of California at Irvine already knew that making rats' dopamine receptors hyperactive caused a surge in anandamide, a lipid that binds to the same receptors in the brain as marijuana.

Now Piomelli's group has examined cerebrospinal fluid from 10 schizophrenic patients, taken for diagnostic purposes at the Medical College of Hannover in Germany. They found that fluid from schizophrenic patients had on average twice as much anandamide as fluid from people who didn't have schizophrenia (NeuroReport, vol 10, p 1665).

One explanation for the higher levels in schizophrenics is that the brain is attempting to compensate for a hyperactive dopamine system. "It's the brain's response to bring this dopamine activity down," says Piomelli. But the brain cannot keep the amount of anandamide high enough to lower dopamine levels, he says.

This might also explain why schizophrenics often smoke marijuana. The drug's active agent, THC, and anandamide both bind to the same receptor, so patients might be treating themselves, he says. But because pot does not act selectively in the brain, Piomelli does not consider it a useful treatment for schizophrenia. "I don't think the patient wants to be high," he says. "I think the patient wants to feel better."

One weakness in the data so far is that five of the patients were taking medication for their symptoms and three others vvere using marijuana daily. The effects of these drugs on endogenous cannabinoid levels is not known. "It is imperative to continue with a Sarger sample," says Piomelli. The researchers are now testing fluid. from more patients to see if the correlation still holds true.