In this Auckland University study, all but one of the stroke patients who were cannabis users also used tobacco regularly.

The author (Dr. P. Alan Barber) openly admits that the study didn't account for tobacco use —how long and how much the young stroke patients had been smoking and how big a role that might have played in stroke risk. The "study" also relied on urine samples, but traces of THC can be found in the urine for at least a whole month after consumption of cannabis.

According to the US National Stroke Association, "Smoking tobacco (at least)doubles the risk for stroke when compared to a non-smoker. It reduces the amount of oxygen in the blood, causing the heart to work harder and allowing blood clots to form more easily."

"Prohibitionists are scraping the bottom of the barrel by claiming that cannabis doubles the risk of stroke, when this result has already been linked to tobacco use. There is nothing scientific about this study and it should be discredited by all rational individuals."
—Norml president Julian Crawford

"Narcotics police are an enormous, corrupt international bureaucracy … and now fund a coterie of researchers who provide them with ‘scientific support’ … fanatics who distort the legitimate research of others.… The anti-marijuana campaign is a cancerous tissue of lies, undermining law enforcement, aggravating the drug problem, depriving the sick of needed help, and suckering well-intentioned conservatives and countless frightened parents."   —William F. Buckley, commentary in The National Review, April 29, 1983, p. 495

Here is Dr. David Allen, a Heart and Stroke specialist, calling for cannabinoid-based medicines to be used throughout America. Not just in emergency rooms and through prescriptions, but also through the ingestion of the whole plant, daily, as a supplement to diet:
www.youtube.com/watch