A third of Irish drug users took HHC before it was banned with 90% experiencing negative effects

Seán McCárthaigh

More than a third of Irish drug users admitted using an addictive cannabis substitute that was sold legally in shops before it was classified as an illicit drug this summer, according to the findings of a new study.

Researchers have expressed concern that the use of hexahydrocannabinol – more commonly known as HHC – might become a public health issue, given that the study’s findings suggest use of the drug has become widespread in Ireland within a relatively short period of time.

The study also revealed that 9 out of 10 drug users in the Republic reported negative consequences from taking HHC, including 14.7 per cent who reported anxiety or panic reactions, while 13.4 per cent felt faint or dizzy and 11.9 per cent reported dissociation or depersonalisation.

Other reactions included memory issues in 11.4 per cent of cases, while 10.2 per cent of users experienced nausea and/or vomiting.

In 3.9 per cent of cases, users experienced hallucinations or psychosis, while 3.6 per cent reported depression, and a further 3.2 per cent suffered withdrawal symptoms.

However, the study revealed that less than 2 per cent of users of HHC sought medical help for any harmful effects of the drug, even though 24 per cent had reported experiencing two or more types of negative effects.

It also found that 36.2 per cent of respondents admitted they had taken HHC at least once in their lifetime, with 33.5 per cent claiming they had used it in the previous 12 months.

It showed 17.8 per cent claimed they had taken the drug within the previous month.

The findings are based on data collected from over 2,300 Irish drug users in the 2024 European Web Survey on Drugs.

The authors of the study, which is published in the International Journal of Drug Policy, noted the market for semi-synthetic cannabinoids, including HHC, is linked to the passage of a US law in 201,8 which legalised hemp cultivation.

Although banned in a number of EU countries, HHC – which is chemically similar to THC, the main psychoactive substance in cannabis – was still legally sold in Ireland as either a vape or in jelly sweets until July, when it was categorised as a controlled drug under the Misuse of Drugs Act.

The study highlighted how HHC was the most commonly reported drug used by regular drug users in Ireland after cannabis, cocaine and ecstasy/MDMA.

The survey showed that males were almost twice as likely to have used HHC as females.

In response to a series of questions about their use of HHC, respondents revealed that the primary motive for first taking the drug was its easy availability in stores.

Almost two-thirds of drug users said they had sourced HHC from a high street shop.

A similar proportion of drug users said they had taken HHC to get high or for fun, with approximately half of respondents claiming they took it to relax or reduce stress.

More than a quarter of HHC users said they took the drug to manage depression or anxiety, while 18 per cent used it to reduce pain or inflammation and just under 6 per cent to manage cannabis withdrawal symptoms.

Commenting on the study’s findings, one of its main authors, Deirdre Mongan of the Health Research Board, said it is possible that the delay in controlling HHC in Ireland had contributed to the drug’s popularity.

Dr Mongan claimed there may also have been a perception among users that HHC was “safer” than cannabis or other controlled synthetic cannabinoids because it could be freely and legally purchased in Ireland until very recently.

She said the issue was concerning as the short and long-term effects of HHC were still unknown, while concern has also been expressed by the EU Drugs Agency that HHC products may contain harmful contaminants.

The study noted that HHC was controlled under the Misuse of Drugs Act rather than the Psychoactive Substances Act.

Dr Mongan said a review of current Irish legislation with regard to emerging psychoactive substances was likely to be required “to ensure that it is fit for purpose.”

A separate recent study also found that 13 per cent of admissions to psychiatric hospitals for psychosis between May 2023 and December 2024 were associated with HHC use.