AIMS AND METHOD: To investigate the impact of the widespread availability and use of the semi-synthetic cannabinoid hexahydrocannabinol (HHC) on hospital admissions owing to psychosis. Medical records of patients admitted for psychotic illness to University Hospital Galway were examined to assess HHC or other illicit drug use before admission.

RESULTS: Of the 214 total admissions for psychotic illness, 28 admissions (13.1%) were preceded by use of HHC, nine of whom used only HHC. Sixteen (34%) admissions of first-episode psychosis were preceded by HHC use, with seven of these using only HHC.

CLINICAL IMPLICATIONS: Clinicians should explicitly enquire about the use of HHC in patients presenting with first-episode and relapse of psychotic illness. Sufficient evidence has now accumulated from research of a link between HHC and psychosis. Such psychoses appear to be more prominent in young people with early-phase psychosis, and highlights the need for authorities to change legislation to avoid further harm.