Pubdate: Mon, 01 Jul 2002
Source: United Press International (Wire)
Copyright: 2002 United Press International
Author: Charles Choi, UPI Science News, New York

Science And Technology Desk


OKAYAMA, Japan -- Genetic anomalies tied with marijuana-activated brain 
chemicals appear linked to schizophrenia, Japanese researchers report.

"This result provides genetic evidence that marijuana use can result in 
schizophrenia or a significantly increased risk of schizophrenia," lead 
researcher Hiroshi Ujike, a clinical psychiatrist at Okayama University, 
told United Press International.

Schizophrenia is one of the greatest mental health challenges in the world, 
affecting roughly one of every 100 people and filling about a quarter of 
all hospital beds in the United States. For years, clinical scientists have 
known that abusing marijuana, also known as cannabis, can trigger 
hallucinations and delusions similar to symptoms often found in 
schizophrenia. Prior studies also show that cannabis used before age 18 
raises the risk of schizophrenia six-fold.

The hallucinogenic properties of marijuana, the researchers explained, are 
linked to a biochemical found abundantly in the brain. The chemical, called 
cannabinoid receptor protein, studs the surfaces of brain cells and latches 
onto the active chemical within marijuana known as THC.

"These sites are where marijuana acts on the brain," Ujike said.

Ujike and his team examined the gene for the marijuana receptor in 121 
Japanese patients with schizophrenia and an average age of 44. When they 
compared this gene in schizophrenics with the same gene in 148 normal men 
and woman of the same average age, they found distinct abnormalities in DNA 
sequences called nucleotides among the schizophrenics. Some of their 
nucleotides in the marijuana receptor gene appeared significantly more 
often than normal while others appeared less frequency.

"This finding is the first to report a potential abnormality of the 
cannabinoid system in schizophrenia," said clinical neuroscientist Carol 
Tamminga at the University of Maryland in College Park. "The importance of 
a finding here cannot be overstated, in that it would form a tissue target 
for drug development and allow targeted treatments to emerge for the illness."

It appears malfunctions in the brain's marijuana-linked circuitry may make 
one vulnerable to schizophrenia, Ujike said. This holds especially true for 
a condition called hebephrenic schizophrenia, which is marked by 
deterioration of personality, senseless laughter, disorganized thought and 
lack of motivation. These symptoms are similar to psychotic behavior 
sometimes triggered by severe cannabis abuse, which could mean the 
marijuana receptors in schizophrenics are far more active than they should be.

Ujike stressed there is no evidence yet these genetic abnormalities can 
affect how the marijuana receptor actually acts in the brain. "We would 
also like to replicate our findings with different ethnic populations and 
more people," he added.

The researchers described their findings in the scientific journal 
Molecular Psychiatry.
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