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Marijuana Use, Schizophrenia Show Similar Patterns in Developing Adolescent Brains: Presented at RSNA

By Ed Susman

CHICAGO, IL -- December 5, 2005 -- Studies using brain diffusion tensor imaging appear to show similar developmental delays or deficits in scans of teenagers who are heavy users of marijuana as in teenagers who have schizophrenia.

"The worst developmental deficit is seen in schizophrenics who are marijuana smokers." said Manzar Ashtari, PhD, Researcher, Zucker Hillside Hospital, Glen Oaks, New York, United States.

In a presentation here at the 91^st scientific assembly and annual meeting of the Radiological Society of North America (RSNA), Dr. Ashtari described her examination of several small groups of subjects in late adolescence -- healthy, non-drug users; teens who had been using marijuana daily for at least 1 year; and schizophrenics.

Diffusion tensor imaging depicts the motion of water molecules in the brain, and Dr. Ashtari and colleagues looked specifically at the arcuate fasciculus, a bundle of fibers in the left frontal lobe.

Her work revealed that repeated exposure to marijuana was related to abnormalities in the development of the fiber pathway, she said in a press briefing on November 30^th. "Because this language/auditory pathway continues to develop during adolescence, it is most susceptible to the neurotoxins introduced into the body through marijuana use," she explained.

The researchers compared the arcuate fasciculus development in the brains of 12 healthy, early adolescents with 12 later adolescents; 11 schizophrenic patients with 17 matched controls; 15 schizophrenic patients who smoke marijuana with 17 matched controls; and 15 marijuana smokers with 15 matched non-drug users.

Among the finding, abnormalities in the arcuate fasciculus seen in those who smoked marijuana or those with schizophrenia were significantly associated with worse working memory function. They had a 45% greater relative risk of having working memory deficits compared to other subjects, and that difference reached statistical significance at the P = .008 level.

"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-researcher Sanjiv Kumar, MD, Assistant Professor of Psychiatry, Albert Einstein College of Medicine, The Bronx, New York, United States.

However, Michael Brant-Zawadzki, MD, Chairman of the Communications Committee of the RSNA, who moderated the press briefing, suggested that the work needs replication with larger numbers of subjects before firm conclusions can be made about how marijuana and schizophrenia are linked.


[Presentation title: The Impact of Recurrent Exposure to Cannabis on Brain Development in Adolescents with Schizophrenia and Healthy Volunteers. Abstract SSQ15-08]

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