Cannabis use was linked to treatment-resistant schizophrenia in a Pakistani hospital cohort | Research

The takeaway

Among 230 schizophrenia patients in Pakistan, ongoing cannabis use was significantly associated with treatment resistance, defined as failure to respond to two adequate antipsychotic trials, even after excluding non-adherent patients.

Psychiatrists treating schizophrenia, substance use disorder specialists, and researchers studying treatment resistance mechanisms.

>60% treatment resistant

What the researchers found

The treatment resistance rate was over 60% in this cohort. Ongoing cannabis use was significantly associated with treatment resistance after controlling for treatment adherence. The study excluded cases where non-adherence could explain treatment failure, strengthening the cannabis-treatment resistance link.

Why it matters

Treatment-resistant schizophrenia is one of the most challenging conditions in psychiatry. If cannabis use contributes to treatment resistance, it identifies a modifiable factor that could improve outcomes for a substantial number of patients.

The numbers in context

230 patients studied. Over 90% male. Treatment resistance rate: >60%. Cannabis use was associated with treatment resistance. Only adherent patients were included to rule out non-compliance as a confound.

How the study worked

Cross-sectional study of 230 schizophrenia patients at a psychiatric hospital in Khyber Pakhtunkhwa, Pakistan. Clinical evaluation using PANSS and CGI scales. Treatment resistance defined as failure to respond to two adequate antipsychotic trials. Adherent patients only.

What this study cannot tell us

Cross-sectional design cannot establish causation. Self-reported cannabis use may be underreported. The heavily male cohort limits generalizability. Specific cannabis types, doses, and duration of use were not detailed. High treatment resistance rate may reflect referral bias at a tertiary hospital.

How to read the evidence

Rated moderate because the study had a reasonable sample size and controlled for adherence, but the cross-sectional design limits causal inference.

When this study was published

Published in 2019. Data from a region in Pakistan with prevalent cannabis use.

The bigger picture

This finding from a region with prevalent cannabis use adds international evidence to the cannabis-schizophrenia relationship. The focus on treatment resistance (rather than just onset or relapse) identifies a clinically important and potentially actionable pathway.

Questions still open

Does cannabis cessation restore treatment responsiveness? Is the association specific to certain antipsychotics? Would the same pattern appear in female patients or other populations?

Common questions

Does cannabis make schizophrenia harder to treat?

This study found an association between ongoing cannabis use and treatment resistance in schizophrenia patients who were otherwise taking their medications as prescribed.

What is treatment-resistant schizophrenia?

When symptoms do not adequately improve after trying at least two different antipsychotic medications at adequate doses and duration.

Could stopping cannabis improve treatment response?

The study did not test this directly, but the association suggests cannabis cessation could be worth investigating as a strategy to improve treatment outcomes.

Read the original research

Association of smoked cannabis with treatment resistance in schizophrenia.

Psychiatry research, 278, 242-247

View on PubMed ↗Publisher’s paper ↗

Citation

Arsalan, Arsalan; Iqbal, Zafar; Tariq, Muhammad; Ayonrinde, Oyedeji; Vincent, John B; Ayub, Muhammad. (2019). Association of smoked cannabis with treatment resistance in schizophrenia.. Psychiatry research, 278, 242-247. https://doi.org/10.1016/j.psychres.2019.06.023