Synthetic cannabinoid use in psychiatric patients and relationship to hospitalisation: A retrospective electronic case register study.

Introduction and objectives: Cannabis use has been associated with psychosis and with poor outcome in patients with mental illness. Synthetic cannabinoids (SCs) have been suggested to pose an even greater risk to mental health, but the effect on clinical outcome has not been directly measured. In this study, we aimed to investigate the demographics and hospitalisation of psychiatric patients who were SC users. Methods: We searched the Biomedical Research Centre Clinical Record Interactive Search register for SC users and age- and sex-matched SC non-users who had been psychiatric patients under the South London and Maudsley NHS Trust. We recorded diagnosis, homelessness, cannabis use and the total number of days admitted as an inpatient to secondary and tertiary mental-health services. Results: We identified 635 SC users and 635 age- and sex-matched SC non-users. SC users were significantly more likely to be homeless (chi(2)=138.0; p<0.0001) and to use cannabis (chi(2)=257.3; p<0.0001) than SC non-users. SC users had significantly more inpatient days after their first recorded use of SCs than controls (M (SD)=85.5 (199.7) vs. 25.4 (92.32); p<0.0001). Post hoc tests revealed that SC non-users who used cannabis had fewer inpatient days than SC users (p<0.0001), and that non-users of both SC and cannabis had fewer inpatient days than SC non-using cannabis users (p=0.02). Conclusions: SC use may lead to an increase in the number of days spent in hospital in patients with psychiatric illness. This highlights the need for clinicians to ask specifically about SC use.