CHICAGO, Nov. 30 /PRNewswire/ -- Heavy use of marijuana may put
adolescents who are genetically predisposed to schizophrenia at greater risk
of developing the brain disorder, according to research presented today at the
annual meeting of the Radiological Society of North America (RSNA).
Using a sophisticated brain imaging technique called diffusion tensor
imaging (DTI), researchers at Zucker Hillside Hospital in Glen Oaks, New York,
studied the brains of groups of adolescents: healthy, non-drug users; heavy
marijuana smokers (daily use for at least one year); and schizophrenic
patients. Unlike magnetic resonance imaging (MRI), which provides a static
picture of brain structures, DTI detects and measures the motion of water
molecules in the brain, which can reveal microscopic abnormalities.
Manzar Ashtari, Ph.D., Sanjiv Kumra, M.D., and colleagues used DTI to
examine the arcuate fasciculus, a bundle of fibers connecting the Broca's area
in the left frontal lobe and the Wernicke's area in the left temporal lobe of
the brain. The investigators found that repeated exposure to marijuana was
related to abnormalities in the development of this fiber pathway, which is
associated with the higher aspects of language and auditory functions.
"Because this language/auditory pathway continues to develop during
adolescence, it is most susceptible to the neurotoxins introduced into the
body through marijuana use," explained Dr. Ashtari, associate professor of
radiology and psychiatry at New York's Albert Einstein College of Medicine.
In the study, DTI was performed on 12 healthy, early adolescent males
compared with 12 late adolescent males to show normal human brain development;
11 schizophrenic patients compared with 17 matched controls; 15 schizophrenic
patients who smoke marijuana compared with 17 matched controls; and 15
marijuana smokers compared with 15 matched non-drug users. The scans revealed
no abnormal developmental changes in the language pathway in the healthy
adolescents, but showed abnormalities in both the marijuana users and
schizophrenic patients.
"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 co-principal-investigator Sanjiv Kumra, M.D., assistant
professor of psychiatry at Albert Einstein College of Medicine.
According to the National Institute on Drug Abuse, approximately 3.1
million Americans age 12 and older use marijuana on a daily or almost daily
basis. In 2004, 5.6 percent of 12th graders reported daily use of marijuana.
Schizophrenia is a chronic, severe and disabling brain disorder that
affects about one percent of the entire population. Although the causes of the
disease have not been determined, it is believed to result from a combination
of environmental and genetic factors.
Drs. Ashtari and Kumra said longitudinal studies are needed to determine
whether these changes in the brain are permanent or change over time. It is
also important to mention that at this time, DTI and MRI are not diagnostic
means for schizophrenia patients or marijuana smokers.
Co-authors are Jinghui Wu, B.S., Kelly Cervellione, M.A., John Kane, M.D.,
Philip Szeszko, Ph.D., and Babak Ardekani, Ph.D.
RSNA is an association of more than 38,000 radiologists, radiation
oncologists, medical physicists and related scientists committed to promoting
excellence in radiology through education and by fostering research, with the
ultimate goal of improving patient care. The Society is based in Oak Brook,Ill.
AT A GLANCE
-- Researchers using diffusion tensor imaging (DTI) have found similar
abnormalities in the brains of adolescents who are daily marijuana
users and adolescents with schizophrenia.
-- The abnormalities were found in a part of the brain still developing
during adolescence that is associated with the higher aspects of
language and auditory functions.
-- The findings also suggest that heavy use of marijuana may lead to
earlier onset of schizophrenia in adolescents who are genetically
predisposed to the disorder.
William R. Caltrider, Jr., President
Center for Alcohol and Drug
Research and Education
International NGO in special consultative status with the
Economic and Social Council of the United Nations
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