A new study published in the International Journal of Drug Policy highlights the rapid rise in the use of hexahydrocannabinol (HHC) in Ireland and the potential public health implications associated with the drug.1 HHC, a semi-synthetic cannabinoid derived from cannabidiol (CBD), was marketed as a legal alternative to cannabis until its control under Irish law in July 2025.

The research, conducted by experts at the Health Research Board (HRB), the Health Service Executive (HSE), the School of Public Health at University College Cork, and the European Drugs Agency (EUDA), analysed data from more than 2,300 adults who took part in the 2024 European Web Survey on Drugs. These participants had used drugs in the previous year and responded to a dedicated module on HHC use.

The findings reveal that 36.2% of respondents reported lifetime HHC use, 33.5% had used the drug in the past year, and 17.8% had used it in the past month. HHC was most commonly sourced from high street shops (62.4%) and online stores (15.7%), reflecting its widespread availability prior to regulation. Vaping was the dominant method of administration (85.4%), followed by edibles such as gummies (34.1%), and smoking (14.5%).

A key factor influencing HHC’s initial use was accessibility: more than 60% of participants cited ease of purchase as their main reason for trying HHC. Many also perceived it as safer than illegal cannabis due to its legal status at the time. Motivations for ongoing use included recreation (62.9%), stress relief (51.9%), and self-medication for issues such as anxiety or pain.

The study also found high levels of self-reported harms from HHC use, with nearly 90% of users experiencing at least one negative effect. The most common harms included anxiety or panic reactions (14.7%), dizziness (13.4%), and dissociation (11.9%). More severe outcomes, such as hallucinations or psychosis, were reported by 3.9% of users.

The prevalence of HHC use in Ireland appears significantly higher than the European average, where last-year use of similar semi-synthetic cannabinoids was around 14%. This pattern mirrors earlier trends in the use of new psychoactive substances (NPS) prior to their control under the Criminal Justice (Psychoactive Substances) Act 2010. Previous legislative actions on NPS have led to sharp declines in their use and related health harms, suggesting that similar outcomes could be expected for HHC following its scheduling under the Misuse of Drugs Acts.

While its legal status has changed, the study authors stress the importance of ongoing monitoring of HHC and related substances through population surveys, hospital and psychiatric data, and treatment services. They also highlight the need for legislative frameworks that can adapt more rapidly to emerging psychoactive substances.

1    Mongan D, Killeen N, Millar SR, Matias J, Keenan E and Galvin B (2025) Hexahydrocannabinol (HHC) use and harms in Ireland: New findings from the 2024 European Web Survey on Drugs. Int J Drug Policy, 145: 105011. Available from: https://www.drugsandalcohol.ie/44244/