A systematic review of the effects of novel psychoactive substances 'legal highs' on people with severe mental illness.

Introduction Novel psychoactive substances (NPS) are synthetic substances that have been developed to produce altered states of consciousness and perceptions. People with severe mental illness (SMI) are more likely to use NPS than people without mental illness, but the short- and long-term effects of NPS are largely unknown. Method We systematically reviewed the literature about the effects of NPS on people with SMI. Results We included 12 case reports, 1 cross-sectional survey and 1 qualitative study. Participants included mostly males aged between 20 and 35 years. A variety of NPS were used, including synthetic cathinones and herbs such as Salvia. The most commonly reported effects of NPS were psychotic symptoms (in some cases novel in form and content to the patients' usual symptoms) and significant changes in behaviour, including agitation, aggression and violence. Patients' vital signs, such as blood pressure, pulse rate and temperature, were also commonly affected. Conclusion NPS potentially have serious effects on people with SMI, but our findings have limited generalizability due to a reliance on case studies. There is a paucity of evidence about the long-term effects of these substances. Further research is required to provide a better understanding about how different NPS affect patients' mental and physical health.