Cannabis-using schizophrenia patients in Asia showed more aggressive behavior | Research

The takeaway

Among Asian patients with schizophrenia, lifetime cannabis use was independently associated with aggressive behavior and was linked to preferential use of long-acting injectable antipsychotics.

Clinicians treating psychosis, researchers studying cannabis and aggression, and those interested in cross-cultural psychiatric findings.

1.58x higher odds of aggressive behavior with cannabis use

What the researchers found

After adjusting for multiple variables, lifetime cannabis use in Asian schizophrenia patients was independently associated with aggressive behavior (aOR 1.58, 95% CI 1.01-2.49) and with long-acting injectable antipsychotic treatment (aOR 1.80, 95% CI 1.44-2.82).

Why it matters

Most cannabis-psychosis research comes from Western populations. This large multi-country Asian dataset provides evidence that the cannabis-aggression link in schizophrenia extends across cultural contexts.

The numbers in context

132 cannabis users vs. 1,756 non-users. Aggressive behavior aOR: 1.58 (95% CI 1.01-2.49, p=.047). Long-acting injectable antipsychotic use aOR: 1.80 (95% CI 1.44-2.82, p=.001).

How the study worked

Cross-sectional analysis of the REAP-AP consortium survey, which collected psychotropic prescription patterns from Asian schizophrenia patients. Compared 132 lifetime cannabis users with 1,756 non-users using binary logistic regression, adjusting for age, sex, region, income, duration of untreated psychosis, and comorbidity.

What this study cannot tell us

Cross-sectional design cannot establish causation. Cannabis use was based on lifetime self-report. The cannabis-using group was much smaller than the non-using group. Cultural factors around cannabis use in Asia may limit generalizability.

How to read the evidence

Moderate: large multi-country consortium with appropriate statistical controls, but cross-sectional design.

When this study was published

Published in 2019.

The bigger picture

The finding that cannabis-using patients were more likely to receive long-acting injectable antipsychotics suggests clinicians may be responding to treatment adherence or behavioral management challenges associated with cannabis use.

Questions still open

Is cannabis causing the aggressive behavior, or are more aggressive patients more likely to seek out cannabis? Does cannabis cessation reduce aggressive episodes? Why are long-acting injectables preferentially used in this group?

Common questions

Does this prove cannabis causes aggression in schizophrenia?

No. The study found an association between lifetime cannabis use and aggressive behavior, but the cross-sectional design cannot determine which came first or prove causation.

What are long-acting injectable antipsychotics?

These are antipsychotic medications given as injections every few weeks instead of daily pills. They are often used when medication adherence is a concern.

Read the original research

Cannabis use correlates with aggressive behavior and long-acting injectable antipsychotic treatment in Asian patients with schizophrenia.

Nordic journal of psychiatry, 73(6), 323-330

View on PubMed ↗Publisher’s paper ↗

Citation

Park, Seon-Cheol; Oh, Hong Seok; Tripathi, Adarsh; Kallivayalil, Roy Abraham; Avasthi, Ajit; Grover, Sandeep; Tanra, Andi Jayalangkara; Kanba, Shigenobu; Kato, Takahiro A; Inada, Toshiya; Chee, Kok Yoon; Chong, Mian-Yoon; Lin, Shih-Ku; Sim, Kang; Xiang, Yu-Tao; Tan, Chay Hoon; Javed, Afzal; Sartorius, Norman; Shinfuku, Naotaka; Park, Yong Chon. (2019). Cannabis use correlates with aggressive behavior and long-acting injectable antipsychotic treatment in Asian patients with schizophrenia.. Nordic journal of psychiatry, 73(6), 323-330. https://doi.org/10.1080/08039488.2019.1632381