Clinical guideline found no antipsychotic can be recommended over another for schizophrenia patients who use cannabis | Research

The takeaway

Evidence-based guidelines using GRADE methodology found insufficient evidence to recommend any specific antipsychotic for schizophrenia patients with cannabis use disorder, while bupropion and varenicline were recommended for those with nicotine use.

Psychiatrists, addiction medicine specialists, and clinicians managing dual-diagnosis patients.

No antipsychotic can be recommended over another for schizophrenia with cannabis use

What the researchers found

For schizophrenia with cannabis use: no antipsychotic (olanzapine, risperidone, haloperidol, or clozapine) could be recommended over another (weak recommendation). For cocaine use: haloperidol reduced craving vs. olanzapine. For alcohol: naltrexone recommended. For nicotine: bupropion and varenicline recommended (strong/moderate). For polydrug: second-generation antipsychotics preferred.

Why it matters

With high rates of cannabis use among schizophrenia patients, clinicians urgently need evidence-based guidance. The finding that no antipsychotic is clearly better for cannabis users highlights a critical evidence gap.

The numbers in context

Cannabis+schizophrenia: no recommendation between olanzapine, risperidone, haloperidol (weak). Clozapine: cannot recommend for cannabis reduction (weak). Nicotine: bupropion and varenicline recommended (strong/moderate).

How the study worked

GRADE-based clinical practice guideline using systematic review of pharmacological and psychological interventions for adult schizophrenia patients with comorbid substance use disorders, structured by PICO framework.

What this study cannot tell us

Evidence quality was generally low to moderate. Limited number of head-to-head trials for cannabis + schizophrenia. Guidelines based on available evidence, which is sparse for cannabis-specific outcomes.

How to read the evidence

Rigorous GRADE methodology applied, but limited by the sparse available evidence for cannabis-specific recommendations.

When this study was published

Published in 2022.

The bigger picture

The lack of evidence-based recommendations for the most common dual diagnosis (schizophrenia + cannabis) underscores the need for dedicated clinical trials in this population.

Questions still open

Should dual diagnosis trials prioritize cannabis + schizophrenia given the prevalence? Would newer antipsychotics (cariprazine, brexpiprazole) perform differently?

Common questions

Which antipsychotic is best for schizophrenia patients who use cannabis?

Current evidence cannot recommend one over another. Olanzapine, risperidone, haloperidol, and clozapine all lack sufficient evidence for superiority in cannabis-using patients.

Are there any strong recommendations?

Yes, but for other substances: bupropion and varenicline received strong/moderate recommendations for schizophrenia patients with nicotine use disorder.

Read the original research

Clinical practice guideline on pharmacological and psychological management of adult patients with schizophrenia spectrum disorders and a comorbid substance use.

Adicciones, 34(2), 110-127

View on PubMed ↗Publisher’s paper ↗

Citation

Arranz, Belen; Garriga, Marina; Bernardo, Miquel; González-Pinto, Ana; Arrojo, Manuel; Torrens, Marta; Tirado-Muñoz, Judith; Fonseca, Francina; Sáiz, Pilar A; Flórez, Gerardo; Goikolea, Jose Manuel; Zorrilla, Iñaki; Cunill, Ruth; Castells, Xavi; Becoña, Elisardo; López, Ana; San, Luis. (2022). Clinical practice guideline on pharmacological and psychological management of adult patients with schizophrenia spectrum disorders and a comorbid substance use.. Adicciones, 34(2), 110-127. https://doi.org/10.20882/adicciones.1504