CANNABIS from the Northern Rivers is among the most potent in the world, sparking fears users could be at risk of developing mental health problems and dependency.
As Australia has one of the highest per-capita rates of cannabis use worldwide, a National Drug and Alcohol Research Centre study, the first of its kind in Australia, analysed levels of THC.
THC, the main psychoactive component of the drug that gets users "stoned", is linked to mental health prob- lems and anxiety.
Researchers examined 232 samples of cannabis seized by NSW police from recreational users and in large outdoor and indoor cultivations.
Study leader Dr Wendy Swift said samples seized from users at Lismore, Byron Bay and Tweed Heads were found to have some of the highest levels of THC.
Cannabis tested also had extremely low levels of cannabidiol, which is thought to counteract some negative effects of THC.
Dr Swift said while no research had linked changes in potency to metal health, it was biologically plausible.
"These results suggest that the profile of cannabis currently used in Australia may make some users vulnerable to mental health problems," she said.
"Cannabis becomes psychoactive once it's heated and high levels of THC can be very adversative to some people, and can induce cannabis psychosis."
Dr Swift said the average THC level found was just under 15%, the same level that cannabis is reclassified as a hard drug in the Netherlands.
She said the research also dispelled the myth that hydroponically grown cannabis was more potent, with northern NSW outdoor-grown samples containing as much THC as hydroponically grown marijuana from Sydney.
Nimbin Hemp Embassy president Michael Baulderstone wasn't surprised cannabis from the region was among the most potent.
"There are a lot of cannabis users out there now who have had time to breed specific plants, and I'm not sure if the potency is a drama, as it means you smoke less," he said.