#7191 Cannabis withdrawal psychosis: a case series and systematic review

<h3>Introduction</h3> Cannabis is the most commonly used recreational drug in United Kingdom (UK), and the association between high-potency cannabis and psychosis is well-established. In regular cannabis users, cessation or rapid reduction of cannabis consumption can be accompanied by a withdrawal syndrome, characterised by anxiety, restlessness, irritability and insomnia. There are a small number of case reports of cannabis withdrawal being temporally associated with the acute onset or relapse of psychosis. Therefore, we aimed to ascertain the presence of cannabis withdrawal-associated psychosis in a patient cohort. <h3>Methods</h3> We conducted a retrospective case series using an electronic case register from a South London mental health trust. Clinical entries in this dataset were searched for terms related to both cannabis and psychosis to identity potential cases. For these cases, free-text entries were reviewed by a psychiatrist to an association between cannabis cessation and psychosis. Clinical characteristics of cases were then further elucidated, and psychotic symptoms were assessed using the Operational Criteria in Studies of Psychotic Illness (OPCRIT) symptom checklist. Additionally, a systematic review of published case reports, case series and other studies was undertaken. <h3>Results</h3> 69 cases of acute psychosis associated with cannabis withdrawal were identified from our health record study. The mean age was 27.3 years and 57 (82.6%) were male. 48 (75%) cases involved a first-presentation of psychosis and 21 (30.4%) concerned relapse of an established psychotic disorder. In 12 (17.4%) cases there was co-morbid use of another substance or alcohol. The majority were daily cannabis users and in 56 (81.2%) cases cannabis discontinuation was abrupt. A range of cannabis withdrawal symptoms were reported; sleep disturbance was the most frequent in 62 (89.9%) individuals. In most cases (48, 70%) psychotic symptoms emerged within one week of cannabis cessation, with the peak occurrence at 4 days. A multitude of psychotic symptoms were reported, of which persecutory delusions in 77% (n = 53) were the most common. Cases who continued to use cannabis after recovery from the acute episode had a higher risk of subsequent relapse than those who continued to abstain (Odds ratio = 14.7 [95% CI: 4.3 to 60.0]; <i>X</i>² = 21.1, p&lt;0.00001). Our systematic review identified 28 cases from 16 studies, and findings were consistent with those identified in our own retrospective case series. <h3>Conclusions</h3> To date, this is the largest case series (n = 97) of cannabis withdrawal-associated psychosis presented. Our findings suggest this condition is more prevalent than previously thought, and its aetiology requires further investigation. We recommend that clinicians consider assessing for recent cessation/reduction in cannabis use when presented with emergence of psychotic symptoms. <h3>Conflicts of interest</h3> None