A leading stroke specialist has said that the high potency cannabis available in Ireland is putting young people at a risk for stroke.

Speaking at the inquest into the death of a 33-year-old Irishman, Joseph Harbison, a consultant stroke physician professor, told Dublin Coroner's Court that over the past three years, doctors at St James's Hospital have seen "five or six cases" of young people having strokes after using herbal cannabis. He warned that the strokes may be linked to an increase in potency of the cannabis.

“The cannabis available in and around Ireland at the moment is typically hydroponically [IN WATER] grown and has a very high potency… I now strongly suspect that we are seeing the consequences of younger people developing an arteriopathy [arterial disease] related to the direct irritant effects of this new potent cannabis,” he said.

On August 17, 2012, Noel Boylan collapsed on Thomas Street in Dublin's city center. He was taken to St James’s Hospital where he was treated for a suspected seizure but later developed a stroke. He died on September 2nd after a blood clot traveled to his lungs.

Prof Harbison requested an autopsy be done on Boylan, who had been a regular cannabis smoker.

The neuropathologist found that the lining of Boylan's blood vessel had “grossly thickened” and blocked off the artery resulting in the stroke. The finding echoed that of another of Prof Harbison's patients, also a heavy cannabis user, whose blood vessel was biopsied outside the brain after surviving a stroke.

Prof Harbison said there was concern that the potency of cannabis available in Ireland is irritating the lining of blood vessels in regular users.

Coroner Dr Brian Farrell concluded that further research into the link between high potency cannabis and stroke is needed.

Prof Harbison told the Irish Times after the inquest that he did not believe that infrequent users of the drug are at risk.

“There is a level of concern that there is an association with particularly heavy users. We are seeing people coming in with strokes where we cannot find any cause but their cannabis use. This case and the other case leads you to think that there is a direct organic effect to it,” he said.