Cannabis use and trauma were linked to psychotic symptoms in schizophrenia but not primary negative symptoms | Research

The takeaway

Among 167 clozapine-treated schizophrenia patients, those with primary negative symptoms (deficit schizophrenia) had significantly lower rates of cannabis use and trauma exposure, suggesting these late-life insults drive psychotic rather than negative symptoms.

Psychiatrists, schizophrenia researchers, and clinical psychologists.

Cannabis use significantly lower in deficit schizophrenia patients (p=0.005)

What the researchers found

Deficit schizophrenia patients had significantly lower cannabis use at first psychotic episode (p=0.005), less physical/sexual abuse (p=0.033), and less crime-related trauma (p=0.012). Summer birth was associated with deficit schizophrenia (p=0.017). Family history, paternal age, sex, and birth weight did not differ.

Why it matters

Understanding that cannabis and trauma are linked specifically to psychotic symptoms rather than primary negative symptoms helps refine schizophrenia subtypes and may have implications for prevention targeting.

The numbers in context

Patients: 167. Cannabis use lower in deficit group (p=0.005). Physical/sexual abuse lower in deficit (p=0.033). Crime-related trauma lower in deficit (p=0.012). Summer birth higher in deficit (p=0.017).

How the study worked

Cross-sectional single-center study of 167 clozapine-treated schizophrenia patients in England assessed with the Schedule for the Deficit Syndrome. Compared risk factors between deficit (primary negative symptoms) and nondeficit groups using logistic regression.

What this study cannot tell us

Cross-sectional design. All patients on clozapine, limiting generalizability to treatment-resistant cases. Retrospective recall of risk factors. Single-center UK study.

How to read the evidence

Specialized clinical cohort with validated assessment tools, but cross-sectional and limited to clozapine-treated patients.

When this study was published

Published in 2022.

The bigger picture

The finding suggests schizophrenia with prominent negative symptoms may be driven more by early neurodevelopmental factors (summer birth), while cannabis and trauma act as later environmental triggers primarily for positive psychotic symptoms.

Questions still open

Could cannabis prevention reduce the burden of positive psychotic symptoms in schizophrenia while having less impact on negative symptoms? What about summer birth drives deficit schizophrenia?

Common questions

Does cannabis affect all schizophrenia symptoms equally?

No. This study found cannabis use was associated with psychotic symptoms (hallucinations, delusions) but not with primary negative symptoms (emotional blunting, social withdrawal).

What does this mean for schizophrenia subtypes?

It suggests schizophrenia with prominent negative symptoms may have different causes (more neurodevelopmental) than schizophrenia driven primarily by psychotic symptoms (more influenced by cannabis and trauma).

Read the original research

Early versus late risk factors for deficit and nondeficit schizophrenia.

Revista de psiquiatria y salud mental, 15(1), 38-46

View on PubMed ↗Publisher’s paper ↗

Citation

Alabaf, Setareh; Kirkpatrick, Brian; Chen, Shanquan; Cardinal, Rudolf N; Fernandez-Egea, Emilio. (2022). Early versus late risk factors for deficit and nondeficit schizophrenia.. Revista de psiquiatria y salud mental, 15(1), 38-46. https://doi.org/10.1016/j.rpsmen.2022.01.006