Susan Lennon MSW, LCSW Content Strategist
Communications Consultant
Specializing in Thought Leadership and B2B/B2C Marketing Communications

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Cannabis Isn't As Harmless As Suggested
USA Weekend Magazine, September 18, 2005
by Susan T. Lennon

  Cannabis is the most widely used illicit drug in the United States. But if you think it’s hot to smoke pot, consider this. Two new studies -- cited below -- show that cannabis damages the vessels in your brain by constricting blood flow – putting you at risk for stroke. It makes no difference whether you smoke it, eat it, or take a pill. The active ingredient – Δ9  tetrahydrocannabinol (THC) – is the culprit. The stronger the concentration – ranging from 1% in some herbal preparations to up 65% in some hashish oils – the greater the danger.

Cannabis has long been associated with harmful changes in the brain, and sophisticated medical tools can now pinpoint how. One study demonstrates that impairment of the brain’s blood flow persists for at least a month after your last high. Nora Volkow, MD, Director of the National Institute on Drug Abuse, says that THC causes blood vessels in the brain to lose their flexibility, which leaves them prone to breakage – and broken brain vessels can lead to stroke. Not fun, strokes cause paralysis, and problems with vision, memory, and speech.  Both long-term and heavy users are at risk.

Another study draws – for the first time – a direct connection between cannabis and stroke. Ruling out other causes, hash smoking apparently set off toxic reactions in the brain arteries, and brain scans confirmed bleeding, blood clots, and stroke in one particular patient.

Neurologist Carlos García-Moncó, MD, one of the study’s authors, recommends that you exercise caution if you mix your marijuana with cigarettes and alcohol. – these also contribute to stroke – especially if you have other risk factors like high blood pressure, diabetes, or heart disease.

Fifteen cases of cannabis-induced stroke are documented, and Dominique Deplanque, MD, PhD, of the Department of Pharmacology at the University of Lille, in France is emphatic: “its non-medical use should be avoided.”

What about medical marijuana? Scientific studies are underway to determine its usefulness and safety, especially as an aid for pain, spasticity, or bladder problems, but for now, the jury is still out. 


1. Recurrent stroke associated with cannabis use, I Mateo, A Pinedo, M Gomez-Beldarrain, J M Basterretxea, J C Garcia-Monco. J Neurol Neurosurg Psychiatry 2005;76:435–437. doi: 10.1136/jnnp.2004.042382

2. Cerebrovascular perfusion in marijuana users during a month of monitored abstinence. Ronald I. Herning, PhD, Warren E. Better, MS, Kimberly Tate, BS and Jean L. Cadet, MD NEUROLOGY 2005;64:488-493

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