Cannabis and stimulant use drove different psychotic symptom trajectories over 10 years after first-episode psychosis | Research

The takeaway

In a 10-year follow-up of 192 first-episode psychosis patients, four distinct symptom trajectories emerged, with frequent cannabis use in the first five years linked to delayed remission and stimulant use linked to relapse.

Psychiatrists, early psychosis intervention teams, and addiction researchers

10-year follow-up of 192 first-episode psychosis patients

What the researchers found

Four trajectories emerged: Stable Remission (54.2%), Delayed Remission (15.6%), Psychotic Relapse (7.8%), and Persistent Symptoms (22.4%). Delayed Remission was associated with frequent cannabis and stimulant use during the first five years, with dose-dependent effects for cannabis but not stimulants. Psychotic Relapse was associated with sporadic stimulant use throughout the full follow-up period.

Why it matters

Understanding which substance use patterns drive specific long-term psychosis trajectories can help clinicians prioritize substance use interventions. The dose-dependent cannabis effect suggests even reduction (not just cessation) may improve outcomes.

The numbers in context

192 participants; 10-year follow-up; 54.2% Stable Remission; 15.6% Delayed Remission; 7.8% Psychotic Relapse; 22.4% Persistent Symptoms; dose-dependent cannabis effect on unfavorable trajectories; all unfavorable trajectories had more schizophrenia diagnoses and longer untreated psychosis

How the study worked

Ten-year follow-up of 192 participants with first-episode psychosis using growth mixture modeling to identify psychotic symptom trajectories. Associations with baseline characteristics and concurrent cannabis/stimulant use during follow-up were tested.

What this study cannot tell us

Observational design cannot prove causation; substance use assessed during follow-up may be a consequence rather than cause of symptoms; 10-year attrition; cannot distinguish cannabis types or potencies; relatively small trajectory subgroups

How to read the evidence

Long-term prospective cohort with data-driven trajectory analysis, though limited by observational design and modest sample sizes within trajectory groups.

When this study was published

2024 study with 10-year follow-up data

The bigger picture

The finding that cannabis has dose-dependent effects while stimulants show binary effects on psychosis trajectories suggests these substances operate through different mechanisms and may require different intervention approaches.

Questions still open

Would structured cannabis reduction interventions during the first five years of psychosis treatment shift patients from the Delayed Remission to Stable Remission trajectory? Why does stimulant use show a different temporal pattern of risk than cannabis?

Common questions

What were the long-term outcomes for first-episode psychosis patients?

Just over half (54.2%) achieved stable remission. About 15.6% eventually remitted but were delayed, 7.8% relapsed after initial improvement, and 22.4% had persistent psychotic symptoms over the 10 years.

How did cannabis and stimulant use affect outcomes differently?

Cannabis had a dose-dependent effect, meaning more frequent use was associated with worse outcomes, particularly delayed remission during the first five years. Stimulant use showed a different pattern: even sporadic use throughout the follow-up period was associated with psychotic relapse. This suggests cannabis reduction (not just cessation) may help, while stimulant avoidance may need to be complete.

Read the original research

Behind the heterogeneity in the long-term course of first-episode psychosis: Different psychotic symptom trajectories are associated with different patterns of cannabis and stimulant use.

Schizophrenia research, 271, 91-99

View on PubMed ↗Publisher’s paper ↗

Citation

Kreis, Isabel; Lagerberg, Trine Vik; Wold, Kristin Fjelnseth; Åsbø, Gina; Simonsen, Carmen; Flaaten, Camilla Bärthel; Engen, Magnus Johan; Lyngstad, Siv Hege; Widing, Line Hustad; Ueland, Torill; Melle, Ingrid. (2024). Behind the heterogeneity in the long-term course of first-episode psychosis: Different psychotic symptom trajectories are associated with different patterns of cannabis and stimulant use.. Schizophrenia research, 271, 91-99. https://doi.org/10.1016/j.schres.2024.07.006