The Acute Effects of Cannabinoids in Patients with Psychotic Illness

People with psychosis and those at clinical high risk (CHR) for this syndrome have significantly higher prevalence of cannabis use compared to the general population. Furthermore, cannabis use can negatively impact the course and treatment outcomes in psychosis. Understanding the acute subjective and cognitive effects of cannabis and cannabinoids in this population is necessary if we are to disentangle the reasons for the increased prevalence of use; and also to help design interventions. There is little evidence to support the ’self-medication’ hypothesis, in its original form. Among principal phyto-cannabinoids, while THC exacerbates positive and cognitive symptoms of psychosis, cannabidiol lacks these effects and may even improve these symptoms. With the liberalization of cannabis laws in many countries, cannabis and cannabis-based products will be more accessible to both individuals with psychotic disorders and those at risk for psychosis. This chapter summarizes the literature regarding acute effects of cannabis and cannabinoids in people at CHR and with established psychosis.