Smoking cannabis affects brain chemistry so seriously it can trigger schizophrenia, scientists warn today.Researchers have found the first evidence that marijuana can cause genetic abnormalities associated with the mental illness, which affects about one in every 100 people.Many scientists have been warning for years that cannabis can trigger hallucinations and delusions similar to symptoms found in schizophrenia.Previous studies have suggested that using the drug before the age of 18 raises the risk of the condition in later life by six-fold.Its ability to cause psychotic conditions is probably related to long-term changes in the brain caused by a substance found in marijuana called tetrahydrocannabinol (THC).
THC affects chemicals in the brain that transmit information from one nerve cell to another.Disrupting the delicate chemical balance can result in memory loss, anxiety and other conditions.The new Japanese research was led by clinical psychiatrist Dr Hiroshi Ujike of Okayama University and reported in the journal Molecular Psychiatry.The team examined the gene-controlling ‘receptors’ in the brain that respond to marijuana in 121 Japanese schizophrenics and a similar number of healthy men and women. ‘These sites are where marijuana acts on the brain,’ said Dr Ujike.
The scientists found distinct abnormalities in DNA among the schizophrenics.Malfunctions in the brain’s marijuana-linked circuitry may make people vulnerable to schizophrenia, and smoking the drug might trigger the condition.Another recent study suggested that using cannabis can damage everyday memory – such as putting names to faces or remembering to pick up car keys.People who smoke the drug between five and 20 times a month have 10 per cent more of such memory problems than non-users. And those who smoke it more than 20 times a month have been found to be 20 per cent more deficient.Despite the concerns, cannabis looks set to be downgraded in Britain from a class B to a class C drug.The change means that traffickers will face a maximum of five years in jail, less than half the present 14-year term.Home Secretary David Blunkett wants to soften the law on cannabis despite warnings that it can act as a gateway to hard drugs.