Heavy marijuana use damages adolescent brains-study

CHICAGO (Reuters) – Adolescents who regularly smoke
marijuana risk damaging a key brain pathway associated with
language development and some predisposed to schizophrenia may
contract the illness early, researchers said on Wednesday.

Brain scans revealed microscopic abnormalities in a region
of the brain that governs higher aspects of language and
listening functions in adolescents who are heavy marijuana
smokers.

Similar damage to the bundle of fibers, called the arcuate
fasciculus, that connect the Broca’s area in the left frontal
lobe and the Wernicke’s area in the left temporal lobe was
found in the brains of marijuana smokers and schizophrenics
studied.

“These findings suggest that in addition to interfering
with normal brain development, heavy marijuana use in
adolescents may also lead to an earlier onset of schizophrenia
in individuals who are genetically predisposed to the
disorder,” said psychiatry professor Sanjiv Kumra of the Albert
Einstein College of Medicine in New York.

The researchers scanned the brains of 114 subjects, 26 of
whom were selected because they were diagnosed schizophrenics.
Of the schizophrenic group, 15 smoked marijuana.

Another 15 subjects were nonschizophrenic adolescent male
marijuana smokers who were matched against nonsmokers. It was
those smokers whose scans showed abnormalities in the language
and listening pathway.

The brain’s language pathway continues to develop during
adolescence and is susceptible to neurotoxins introduced
through marijuana use, the researchers said.

A scanning technique called diffusion tensor imaging that
detects and measures the motion of water molecules in the brain
was used in the study, which was presented at the annual
meeting of the Radiological Society of North America. The
technique is not used to diagnose schizophrenia.

Roughly 3 million Americans aged 12 and older use marijuana
on a daily or almost daily basis, according to the National
Institute on Drug Abuse. The researchers said longer-term
studies were needed to determine if the brain abnormalities
observed in adolescents were permanent or not.