What is the recommended treatment for a patient with cannabis-induced psychosis admitted to the inpatient setting?

Treatment of Cannabis-Induced Psychosis in the Inpatient Setting

Initiate treatment with low-dose atypical antipsychotic medication, specifically risperidone 2 mg/day or olanzapine 7.5-10 mg/day, as first-line pharmacological management for cannabis-induced psychosis requiring inpatient admission. 1, 2

Initial Assessment and Safety Evaluation

Before initiating antipsychotic treatment, perform a focused assessment to rule out medical emergencies and alternative causes of psychosis:

• Evaluate level of consciousness and orientation to distinguish psychosis from delirium, which requires different urgent management 3
• Assess for focal neurological deficits suggesting structural brain lesions requiring urgent imaging 3
• Rule out central nervous system infections, traumatic brain injury, and metabolic encephalopathy 4, 3
• Screen for alcohol or benzodiazepine withdrawal, which can cause both psychosis and life-threatening seizures requiring immediate benzodiazepine treatment 3
• Evaluate risk of self-harm or aggression to confirm appropriateness of inpatient admission 1, 4

Pharmacological Management Algorithm

First-Line Treatment

Start with atypical antipsychotics at the following initial target doses:

• Risperidone 2 mg/day (first-line option) 1, 2, 5
• Olanzapine 7.5-10 mg/day (first-line option) 1, 2, 6, 5

These doses are effective while minimizing extrapyramidal side effects, which is critical for future medication adherence 1, 2

Dosing Principles

• Avoid large initial doses—they increase side effects without hastening recovery 4, 3
• Any immediate effects are due to sedation; true antipsychotic effects emerge after 1-2 weeks 4
• Increase doses only at widely spaced intervals (14-21 days after initial titration) if response is inadequate 1, 2
• Maximum doses should not exceed 4 mg/day risperidone or 20 mg/day olanzapine in first-episode patients 1, 2
• Consider short-term benzodiazepines as adjuncts to manage acute agitation during stabilization 4

Treatment Duration Before Reassessment

• Implement treatment for 4-6 weeks using adequate dosages before determining efficacy 4, 3
• If symptoms persist after an adequate trial, review reasons for treatment failure including medication adherence and ongoing cannabis use 4, 2

If First-Line Treatment Fails

If no response after 4-6 weeks or if side effects are unmanageable:

• Switch to a different antipsychotic with a different pharmacodynamic profile 4
• Consider aripiprazole as a second-line option, which has demonstrated effectiveness in cannabis-induced psychotic symptoms 5, 7
• For patients with treatment-resistant symptoms after two adequate trials (at least 4 weeks each), consider clozapine 1, 4, 5

Recent real-world evidence specifically for cannabis-induced psychosis shows that aripiprazole LAI (aHR 0.27), olanzapine LAI (aHR 0.28), clozapine (aHR 0.55), and oral aripiprazole (aHR 0.64) are particularly effective for relapse prevention. 5 This 2025 Swedish cohort study of 1,772 patients with cannabis-induced psychosis provides the strongest evidence for specific medication choices in this population.

Critical Management Considerations

Cannabis Abstinence is Essential

• Complete abstinence from cannabis after the first episode is critical for good recovery—patients who completely abstained had no relapse of psychiatric illness 8
• All patients who relapsed to cannabis use had recurrence of illness 8
• Abstinence later in the course does not improve outcomes as significantly as early abstinence 8
• Antipsychotic treatment does not worsen cannabis cravings and may be beneficial 9

Long-Term Treatment Planning

• If the patient responds well, continue antipsychotic treatment for at least 3-6 months before attempting to taper 4
• Consider long-acting injectable antipsychotics given the high rates of non-adherence and relapse in this population 1, 5
• Patients with predominantly non-affective psychotic features have a 50% risk of progressing to an independent psychiatric disorder, compared to only 7.7% with predominantly affective features 8

Family Involvement and Psychosocial Support

• Include families in the assessment process and treatment planning from the outset 1, 4, 3
• Provide families with emotional support and practical advice, as they are typically in crisis at treatment initiation 1, 4
• Develop supportive crisis plans to facilitate recovery and treatment acceptance 1, 4
• Ensure continuity of care with the same treating clinicians for at least the first 18 months 4, 3

Common Pitfalls to Avoid

• Do not use typical antipsychotics as first-line treatment—they have higher rates of extrapyramidal side effects even at low doses, which reduces adherence 1, 2
• Do not delay treatment until a crisis develops—early intervention allows engagement in a safer, more positive context 1, 4
• Do not switch medications too early (before 4-6 weeks)—allow adequate time for therapeutic response 4, 3
• Do not miss delirium—fluctuating consciousness and disorientation distinguish delirium from psychosis and require different urgent evaluation 3
• Do not underestimate the importance of cannabis abstinence—medication alone without abstinence leads to poor outcomes 8

Prognostic Factors

Poor prognosis is associated with:

• Early onset of cannabis use (≤18 years) 8
• Younger age at onset of first episode 8
• Positive family history of psychiatric illness 8
• Being unmarried and lower socioeconomic status 8
• Predominantly non-affective psychotic features 8