Cannabis use and psychosis — dual formulation to integrated care (MEQ)

(i) Differential / working dual formulation. Not pure intoxication alone (symptoms span weeks with organised delusions and commentary). Working possibilities: cannabis-associated first presentation — cannabis-induced psychotic disorder versus primary first-episode psychosis with CUD comorbidity. Hold dual formulation until course after reduced use clarifies independence. Also exclude delirium/organic (currently low probability if alert and afebrile without red flags) and consider affective psychosis if mood becomes primary. Other substances on history. ^[1][5]

(ii) Assessment priorities. Risk (suicide, violence, vulnerability, driving, childcare); collateral and premorbid function; cannabis timeline — age of onset (15), frequency (most nights), high-THC potency, route, last use, withdrawal, CUD criteria; MSE with examples; capacity/legal status under local statute; baseline metabolic panel and ECG before antipsychotics; urine screen supports exposure but does not timestamp onset or measure potency. ^[1][5]

(iii) Management. Safety and least-restrictive setting that is still safe; do not withhold antipsychotics solely for positive UDS. Example start if psychosis warrants treatment: aripiprazole 10 mg orally daily after baselines, counsel akathisia, review within days, trial about 4–6 weeks with adherence support. Parallel CUD package: motivational interviewing, CBT for cannabis, family psychoeducation, contingency management if available — psychosocial interventions have the best evidence base for CUD. Address withdrawal (irritability, insomnia, craving) supportively. Refer early intervention / dual-diagnosis pathway. Relapse plan must name cannabis continuation as a risk amplifier. ^[3][4][5]

(iv) Family counselling. High-THC daily use is associated with increased psychotic disorder risk and contributes to incidence variation (EU-GEI framing); adolescent onset is a higher-risk window. Some substance-induced psychoses convert later to schizophrenia or bipolar disorder — resolution now does not mean zero follow-up. Continued use after onset raises relapse risk. Avoid fatalism ("schizophrenia forever on day one") and avoid minimisation ("just weed"). Crisis contacts, named review, education and study supports. ^[1][2][4]