Misuse of certain drugs is a common precipitant of first-episode psychosis (FEP). Substance misuse is known to exacerbate psychotic symptoms, and it is unclear if substance misuse at the time of initial presentation impacts outcomes of care in FEP. Here, in this quality improvement project (QIP), we aimed to quantify the prevalence of drug misuse within an outpatient early intervention service (EIS) and determine the outcomes (in terms of time-to-discharge and discharge destination) of service users based on their substance misuse history.

In this QIP, we randomly sampled 100 patients referred to and discharged from an outpatient service for psychosis (Barnet EIS). We excluded patients who were referred to the service but were discharged due to referral rejection, non-attendance at psychiatry review and/or other reasons. Data regarding demographic and clinical information, the nature of substance misuse, and discharge destinations were obtained through a review of electronic health records, including GP letters and hospital notes. The time-to-discharge was defined as the time between referral acceptance and discharge from EIS. As this work is part of a QIP, written consent was not obtained to conduct this project.

Of 100 patients obtained from the discharged caseload, 38 patients were accepted and reviewed in Barnet EIS. 24 patients (63.2%) had no substance misuse history at the time of initial FEP, while 14 patients (36.8%) had some substance misuse history. Of the 14 patients with substance misuse, cannabis was most frequently used. The average age of patients was 27.2 ± 1.4 years old. The age of onset of psychosis was similar between patients with and without substance misuse (two-sample t-test, p = 0.74).

In terms of discharge destination, patients with and without substance misuse were discharged back to their GPs at similar proportions (chi-square test, p = 0.81). Finally, the number of days patients spent under the care of Barnet EIS was similar between patients with and without substance misuse (two-sample t-test, p = 0.54).

In this QIP, over 30% of patients presenting with FEP reported substance misuse. The most common recreational drug used was cannabis. Discharge destinations and the time spent in EIS were broadly similar between patients with and without substance misuse. The relatively high rates of substance misuse in FEP found in this study have important implications for commissioning additional services – such as urine drug testing or drug liaison services – within EIS teams.