Doctors are warning young synthetic cannabis smokers they are putting themselves at risk of having a stroke.
A 25-year-old prison inmate in the US has been left with a permanent disability after suffering a stroke, despite no family history of heart disease or risk factors, according to an article in journal BMJ Case Reports.
Wardens found him collapsed on the bathroom floor alongside a "suspicious" substance, and he was known to have dabbled in synthetic cannabis over the previous six months.
A stroke happens when blood is prevented from reaching the brain, or a blood vessel in the brain bursts. It usually strikes older people.
Testing showed the prisoner also had a prior heart attack.
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Doctors attributed both the heart attack and stroke to his synthetic cannabis use, but say more research is needed to see if this was a one-off case or there really is a direct link.
But they fear it won't be easy, with so many different formulations of synthetic drugs on the black market.
"The diversity among different drugs under this common umbrella of 'synthetic marijuana' will remain a barrier to successful testing of all chemicals with a single battery of tests," they wrote.
Synthetic drugs aim to emulate the high given by traditional marijuana, but are much more dangerous - the deaths of dozens of Kiwis have been linked to the drugs. They can be up to 50 times stronger than natural cannabis.
"Even a single smoke of synthetic is the equivalent of up to 15 normal joints," Wellington Hospital emergency medicine specialist Dr Paul Quigley told Newshub last year.
"This is why the effect is so very different and so very dangerous."
The scientist who first developed them for research purposes, John Huffman, in 2011 said users are "stupid" and "playing Russian roulette".