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Cannabis Exposure Not Toxic To The Developing Brain, Study Says
NORML | 05/11/2006

Orangeburg, NY: Moderate-to-heavy adolescent cannabis use does not appear to be damaging to the developing brain, according to clinical trial data published this week in the Harm Reduction Journal.

Researchers at the Nathan S. Kline Institute for Psychiatric Research and the New York University School of Medicine found "no ... evidence of cerebral atrophy or loss of white matter integrity" attributable to cannabis use in the brains of frequent adolescent marijuana users compared to non-using controls, after performing MRI (magnetic resonance imaging) scans and other advanced imaging technology.

Participants in the study self-reported having used marijuana at least two-to-three times per week for several years prior to age 18, but were not current users. Study volunteers were matched for sex, age, and social class with control subjects with no history of cannabis use. Investigators scanned participants' brains using diffusion tensor imaging (DTI), a sophisticated MRI technique that can detect the degradation of nerve fibers (e.g. white matter) that carry information between brain cells.

"It is concluded that frequent cannabis use is unlikely to be neurotoxic to the normal developing adolescent brain," researchers determined. Investigators further added that their findings, though preliminary, "have implications for refuting the hypothesis that cannabis alone can cause psychiatric disturbance such as schizophrenia by directly producing brain pathology."

Two prior MRI studies published in 2000 and 2005 also reported no difference in gray or white matter volumes in heavy adult cannabis users compared to non-users.

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