Cannabis-related schizophrenia may require less medication but leads to more hospitalizations | Research

The takeaway

In a nationwide Danish study of over 35,000 people with schizophrenia, those whose psychosis was preceded by cannabis use disorder used less antipsychotic medication but had more psychiatric hospitalizations.

Psychiatrists, psychosis researchers, and mental health policy makers

35,714 schizophrenia patients, 11.5% cannabis-related

What the researchers found

Among 35,714 people with incident schizophrenia (11.5% cannabis-related), propensity-score matched analysis showed cannabis-related cases used significantly less antipsychotics and benzodiazepines. In unmatched analysis, the cannabis-related group had more days admitted, though this was markedly attenuated after matching.

Why it matters

If cannabis-related schizophrenia responds differently to treatment, it could have implications for how clinicians approach medication decisions and hospital planning for this subgroup.

The numbers in context

35,714 people with incident schizophrenia; 4,116 (11.5%) cannabis-related; lower antipsychotic and benzodiazepine use after propensity matching; more hospitalization days in unmatched analysis, attenuated after matching

How the study worked

Nationwide Danish registry study identifying all individuals with incident schizophrenia from 1995 to 2016. Cannabis-related schizophrenia was defined by a cannabis use disorder diagnosis preceding schizophrenia. Cases were compared to both all non-cannabis-related patients and propensity-score matched controls.

What this study cannot tell us

Registry data cannot determine if differences reflect distinct biology or behavioral patterns like treatment non-adherence; cannabis use disorder diagnosis may not capture all cannabis-related cases; propensity matching cannot account for unmeasured confounders

How to read the evidence

Large nationwide registry study with propensity-score matching, though limited by inability to distinguish biological from behavioral explanations.

When this study was published

2024 publication analyzing 1995-2016 data

The bigger picture

The finding that cannabis-related schizophrenia may represent a distinct clinical entity supports growing interest in understanding whether the route to psychosis matters for treatment and prognosis.

Questions still open

Is the lower medication use a sign that cannabis-related schizophrenia is a milder subtype, or does it reflect reduced treatment adherence? Would cannabis cessation improve outcomes in this subgroup?

Common questions

How did cannabis-related schizophrenia differ from other cases?

After propensity-score matching to account for other differences between groups, people whose schizophrenia was preceded by cannabis use disorder used significantly less antipsychotic medication and benzodiazepines. The initial finding of more hospitalization days was largely explained by other factors once matching was applied.

Does this mean cannabis causes a different type of schizophrenia?

The researchers suggest cannabis-related schizophrenia may be a distinct disorder in terms of prognosis, but they cannot determine whether the differences stem from different underlying biology or from behavioral factors like reduced treatment-seeking among cannabis users.

Read the original research

Use of antipsychotic medication, benzodiazepines, and psychiatric hospitalization in cannabis-related versus cannabis-unrelated schizophrenia - a nationwide, register-based cohort study.

Psychological medicine, 54(10), 2634-2643

View on PubMed ↗Publisher’s paper ↗

Citation

Hjorthøj, Carsten; Stürup, Anne; Karlsen, Mette; Speyer, Helene; Osler, Merete; Ongur, Dost; Nordentoft, Merete. (2024). Use of antipsychotic medication, benzodiazepines, and psychiatric hospitalization in cannabis-related versus cannabis-unrelated schizophrenia - a nationwide, register-based cohort study.. Psychological medicine, 54(10), 2634-2643. https://doi.org/10.1017/S0033291724000758