Cannabis use at baseline and persistent use after a first psychotic episode were associated with more severe diminished expression symptoms over 10 years of follow-up.
Early intervention psychosis teams, psychiatrists, and substance use counselors working with psychosis patients.
10-year follow-upshowing persistent cannabis use associated with more severe diminished expression in first-episode psychosis
What the researchers found
Cannabis use at baseline was associated with long-lasting higher symptom load for diminished expression but not apathy. Persistent cannabis use further strengthened this association, implying a causal relationship.
Why it matters
Negative symptoms like diminished expression are among the most disabling features of psychosis and respond poorly to treatment. Reducing cannabis use may be a modifiable factor to improve outcomes.
The numbers in context
351 participants with first-episode non-affective psychosis followed at baseline, 1 year, and 10 years. Both symptom dimensions decreased over time, with most improvement from baseline to 1 year.
How the study worked
Longitudinal cohort study with linear mixed models examining trajectories of two negative symptom dimensions over 10 years, with cannabis use as a predictor while controlling for other secondary negative symptom sources.
Who was studied
351 participants with first-episode non-affective psychosis followed for 10 years.
What this study cannot tell us
Observational design cannot definitively prove causation. Cannabis use assessment may not capture full patterns. Attrition over 10 years may bias results.
How to read the evidence
Long-term longitudinal cohort with appropriate statistical controls; strong observational evidence.
When this study was published
Ten-year longitudinal study from first psychotic episode.
The bigger picture
This study distinguishes between two types of negative symptoms and shows cannabis selectively worsens diminished expression, providing targeted rationale for cannabis cessation interventions in early psychosis.
Replication
Long follow-up strengthens findings; replication in other first-episode cohorts would be valuable.
Funding
Not specified in abstract
Conflicts of interest
Not specified in abstract
Questions still open
- Why does cannabis affect diminished expression but not apathy?
- Would cannabis cessation programs improve negative symptom outcomes in first-episode psychosis?
Read the original research
The trajectory of two negative symptom dimensions in first-episode psychosis and the role of cannabis use: A 10-year follow-up study.
Schizophrenia research, 252, 317-325
Citation
Ihler, Henrik Myhre; Lyngstad, Siv Hege; Gardsjord, Erlend Strand; Widing, Line Hustad; Flaaten, Camilla Bärthel; Åsbø, Gina; Wold, Kristin Fjelnseth; Engen, Magnus Johan; Simonsen, Carmen; Ueland, Torill; Lagerberg, Trine Vik; Melle, Ingrid; Romm, Kristin Lie. (2023). The trajectory of two negative symptom dimensions in first-episode psychosis and the role of cannabis use: A 10-year follow-up study.. Schizophrenia research, 252, 317-325. https://doi.org/10.1016/j.schres.2023.01.024