Both the prevalence of cannabis use and the potency of cannabis (i.e., the concentration of delta-9-tetrahydrocannabinol [THC]) has steadily increased in the United States (US) over the past 20 years (ElSohly et al., 2016; Hasin and Walsh, 2021; Boakye et al., 2021). The increase in cannabis use and potency are major public health issues, given that increased exposure to THC increases the risk of a number of adverse mental health outcomes (Petrilli et al., 2022). In particular, daily cannabis use and high potency use are strongly associated with both the development of psychotic illness and the progression of pre-existing psychotic illness (Forti et al., 2019). Further, cannabis use is common among individuals with a psychotic illness; an estimated 33.7% of individuals report using cannabis at index presentation for first episode psychosis (FEP) and 26.2% of individuals with schizophrenia meet the criteria for cannabis use disorder (Myles et al., 2016; Hunt et al., 2018). Given the significant morbidity and premature mortality associated with schizophrenia spectrum disorders (SSDs), examining the impact of the increasing trends in cannabis use and potency of cannabis in this vulnerable patient population is critically indicated (Petrilli et al., 2022; He et al., 2020; Hjorthøj et al., 2017).

Cannabis use is associated with negative outcomes among individuals with a psychotic illness (Beaudoin et al., 2020, González-Pinto et al., 2011, Scheffler et al., 2021, Schoeler et al., 2016a, Schoeler et al., 2022). Observational and experimental evidence support a dose-response relationship between THC exposure and positive psychotic symptoms among both healthy volunteers and individuals with a SSD (Hindley et al., 2020; Schoeler et al., 2016a; Ganesh et al., 2020; Ruiz-Veguilla et al., 2013; Schoeler et al., 2022). Meta-analytic evidence supports a positive association between ongoing cannabis use after FEP and increased risk of relapse of psychotic symptoms, longer inpatient psychiatric (IP) hospitalizations, and increased severity of positive symptoms on clinical rating scales (Schoeler et al., 2016a). Further, continued cannabis use after FEP is associated with an increased risk of disengagement in outpatient care and worse functional outcomes compared to patients who stopped using or never used cannabis (Schoeler et al., 2016; Scheffler et al., 2021; González-Pinto et al., 2011; Doyle et al., 2014). The increased availability of cannabis may also impact the use of acute psychiatric services for psychosis. The rates of hospitalizations for psychosis associated with cannabis use are higher in states with more liberal recreational cannabis laws (Moran et al., 2022). In Colorado, where cannabis has been legalized for recreational use since 2012, the number of recreational cannabis dispensaries is positively associated with number of psychosis-related emergency department (ED) visits among individuals with SSDs (Wang et al., 2022). Despite the association between increased availability of cannabis and ED visits for psychosis, there is a paucity of work exploring the impact of cannabis use on the ED course for individuals presenting with psychosis.

Both restraints and parenteral medication administration are often used to decrease agitated and/or aggressive behaviors in the ED; however, these 2 interventions can cause iatrogenic trauma for both patients and ED providers (Cusack et al., 2018; Bonner et al., 2002). Physical restraint use has also been associated with increased ED length of stay and subsequent delay in IP hospitalization among patients presenting to the ED for acute psychiatric care (Warren et al., 2016; Chang et al., 2012). Despite the clinical importance of these outcomes in the ED, the association between cannabis use on the risk of physical restraint, parenteral medication administration, IP hospitalization among patients presenting to the ED with psychosis is unknown. Prior studies examining the impact of cannabis use on other markers of acute agitation and/or aggressive behavior among individuals with a SSD are largely limited to psychiatric inpatient and outpatient populations, and not those in the acute ED setting (Scheffler et al., 2021; Park et al., 2019; Beaudoin et al., 2020; Hachtel et al., 2020; Schoeler et al., 2016b; Maremmani et al., 2004; Moulin et al., 2018).

In this study, we explore the relationship between cannabis use and physical restraint and parenteral medication use in the ED among patients presenting for psychosis. We also examine whether cannabis use impacts the risk of IP hospitalization and repeat ED visits for psychosis. We hypothesize that an increased proportion of ED visits with positive urinary THC screen will be associated with physical restraint use and parenteral antipsychotic and/or benzodiazepine administration compared with individuals with negative urinary THC screens. Secondly, we hypothesize positive urinary THC screen will be associated with a greater likelihood of (1) IP psychiatric hospitalization and (2) a repeat ED visit for psychosis within 90 days.