People With Atypical Psychosis Share More Risk Factors With Schizophrenia Than Bipolar Disorder | Research

The takeaway

In a study of 1,099 people with psychotic disorders, those with atypical presentations (PNOS) had early cannabis use rates and academic difficulties more similar to schizophrenia than to psychotic bipolar disorder.

People interested in the relationship between early cannabis use and different types of psychotic disorders

1,099 participants across 3 diagnostic groups

What the researchers found

17.5% of PNOS participants and 11.5% of schizophrenia spectrum participants used cannabis before age 16, compared to only 5.3% of psychotic bipolar participants. PNOS and schizophrenia groups also had poorer premorbid academic functioning than the bipolar group.

Why it matters

Psychotic disorder NOS is a common but poorly understood diagnosis. Understanding whether these patients look more like schizophrenia or bipolar patients in their early histories can guide treatment decisions and help predict outcomes.

The numbers in context

1,099 participants total; 17.5% of PNOS used cannabis before 16 vs 11.5% SSD vs 5.3% PBD; premorbid academic functioning significantly worse in PNOS and SSD vs PBD (F=7.81, p<0.05); childhood adversity rates were high across all three groups with no significant differences

How the study worked

Cross-sectional study of 1,099 participants from the Norwegian TOP-study: 688 with schizophrenia spectrum disorders, 274 with psychotic bipolar spectrum disorders, and 137 with psychotic disorder not otherwise specified (PNOS). Assessed using SCID-I diagnostic interviews, Premorbid Adjustment Scale, cannabis use history, and Childhood Trauma Questionnaire.

What this study cannot tell us

Cross-sectional design cannot establish whether early cannabis use contributed to the psychotic disorder. Self-reported cannabis use history may be subject to recall bias. PNOS is a heterogeneous diagnostic category.

How to read the evidence

Large sample from a well-established research cohort, but cross-sectional design limits causal inference

When this study was published

2022 study

The bigger picture

This adds to evidence that early cannabis use clusters with certain psychosis subtypes. The finding that PNOS patients resemble schizophrenia patients more than bipolar patients suggests these conditions may share developmental pathways.

Questions still open

Does early cannabis use contribute to the development of PNOS, or do shared genetic vulnerabilities explain both? Would reclassifying PNOS patients based on premorbid factors improve treatment outcomes?

Common questions

Does cannabis before age 16 cause psychosis?

This study cannot answer that question directly. It found an association between early cannabis use and certain psychosis subtypes, but the cross-sectional design cannot determine causation.

Were childhood trauma rates different across the groups?

No. All three groups had similarly high rates of childhood adversity, suggesting trauma is a shared risk factor across psychotic disorders regardless of subtype.

Read the original research

Premorbid characteristics of patients with DSM-IV psychotic disorders.

Comprehensive psychiatry, 115, 152310

View on PubMed ↗Publisher’s paper ↗

Citation

Widing, Line; Simonsen, Carmen; Flaaten, Camilla B; Haatveit, Beathe; Vik, Ruth Kristine; Wold, Kristin F; Åsbø, Gina; Ueland, Torill; Melle, Ingrid. (2022). Premorbid characteristics of patients with DSM-IV psychotic disorders.. Comprehensive psychiatry, 115, 152310. https://doi.org/10.1016/j.comppsych.2022.152310