Synthetic cannabis driving mental health issues, warns HSE official

HSE national clinical lead on addiction Eamon Keenan said it could be more effective to regulate psychoactive substances through blanket bans, as opposed to waiting for a given compound to be extensively analysed and then added to the Misuse of Drugs Act.

HSE national clinical lead on addiction Eamon Keenan has warned an influx of synthetic cannabis products is causing more individuals to present with mental health problems.

Professor Keenan said Ireland can often be left playing catch-up when it comes to the regulation of harmful synthetic cannabinoids.

“You can order [synthetic cannabis products] online, you can order them in the black market… we've had a concern that some shops may be selling some products that can cause mental health problems, and they may be legal,” he said.

He said there had been a marked increase in such cannabis products, and the "drug market" is changing.

“With the legislation in Ireland, some of these are legal, some of them are illegal,” said Prof Keenan, adding it was possible to freely buy THC-like products online.

Prof Keenan pointed to hexahydrocannabinol (HHC), a semi-synthetic cannabinoid produced from CBD, the non-intoxicating compound found in cannabis plants. The chemical structure of HHC mimics that of THC, the naturally occurring psychoactive element of cannabis, and produces a similar ‘high’. 

THC is classified as a controlled substance under the Misuse of Drugs Act, but HHC was not outlawed until July 2025.

A study published by the International Journal of Drug Policy last year suggested a lapse in regulating HHC may have resulted in an uptick in its popularity.

“I think our legislation needs to be a lot more agile, and that does require policy change and work across Government departments, including justice, including health, in relation to introducing much more quickly legislation to take these products off the shelves,” said Prof Keenan.

Do we know exactly what is being sold in these vape shops? Looking online at some of them, it does seem that you can get a range of substances with THC-like effects.

Prof Keenan said it could be more effective to regulate psychoactive substances through blanket bans, as opposed to waiting for a given compound to be extensively analysed and then added to the Misuse of Drugs Act.

“[Synthetic cannabinoids] are driving presentations to our services — young people with anxiety, with depression… in some cases we do see confusion, cognitive, effects and acute transient psychosis," said Prof Keenan.

“These synthetic cannabinoids are much more potent than traditional cannabis or traditional THC.

“We have seen recently vapes that were handed in for analysis, which contained synthetic cannabinoids that were associated with harm.”

According to figures released by Ireland’s Health Research Board, treatment demand for new psychoactive substances increased by 50% in 2025, from 170 cases in 2024 to 256 last year.