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The possible health risks of long-term use of synthetic cannabis have begun to emerge - with the risk of suicide and self-harm in users alarming health professionals.
The National Poisons Centre has received an increasing number of calls associated with long-term use of synthetic cannabis products such as Kronic.
Toxicologist Dr Leo Schep said neuropsychiatric effects following long-term use such as anxiety, aggression and psychosis had been noted for some time.
"Recently we have also seen a newer trend emerge with patients experiencing ongoing paranoia linked with suicidal ideations."
An overseas peer-reviewed paper published in the past few weeks had noted the same link, he said.
Synthetic cannabis products contain dried plant matter coated or soaked with cannabinoids - man-made chemicals that mimic the effect of THC, one of the ingredients in cannabis.
Little is known about both the short-term and long-term effects of consuming the chemicals, including whether any effects are irreversible.
New Zealand Drug Foundation executive director Ross Bell said what was clear was that the products were linked with cannabis in name only.
Recent research in Japan found a product contained three chemicals with wildly different effects - one cannabis-like, one hallucinogenic, and the other a methamphetamine-like buzz.
"People assume that just because it is called synthetic cannabis, it must be just like the real plant cannabis, and have the same kind of effects.
"They are thinking it's legal and safe and just like pot. And it absolutely isn't. So I'm not surprised that the National Poisons Centre are beginning to get the calls that they are."
Associate Health Minister Peter Dunne said the recent calls to the poisons centre were of "real concern".
He said he would seek further information from health officials on the issue.
In 2011 the Government banned all existing synthetic cannabis products, including industry-leader Kronic, which had been sold in dairies.
However, new products have skirted the ban by having a slightly altered chemical make-up.
The bans are an interim measure while the Government works on an overhaul of the Misuse of Drugs Act. Manufacturers will ultimately have to prove the safety of their products before they can be sold.
Mr Dunne said he expected the new drug regime to take effect from August.
- Nicholas Jones of the New Zealand Herald