Cannabis Users Who Reduced Use After First Psychotic Episode Had the Best Symptom Improvement | Research

The takeaway

Among 502 first-episode psychosis patients, cannabis use was associated with younger onset and manic symptoms, and those who reduced use after treatment contact showed the greatest symptom improvement at one year.

Read this if you or someone you know has experienced psychosis and uses cannabis.

Cannabis reducers showed greater symptom improvement than both continued users and non-users at 1 year

What the researchers found

In 502 patients with first-episode psychosis tracked across London-based Early Intervention teams, cannabis use level was associated with younger age at presentation to services and with manic symptoms and conceptual disorganization, but not with delusions, hallucinations, negative symptoms, or daily functioning.

The most striking finding was in the longitudinal data: cannabis users who reduced or stopped their use following initial contact with psychiatric services showed the greatest improvement in symptoms at one year, compared to both continued users and non-users. Continued cannabis users remained more symptomatic than non-users at follow-up.

This pattern suggests cannabis use actively worsens the course of psychosis and that reducing use leads to better outcomes.

Why it matters

This is one of the larger naturalistic studies showing that cannabis reduction after first-episode psychosis is associated with better outcomes. The finding that reducers improved more than non-users suggests cannabis was actively suppressing their recovery, and its removal allowed greater therapeutic gains.

The numbers in context

502 first-episode psychosis patients. 7 London Early Intervention teams. Cannabis use associated with younger presentation and manic symptoms. Greatest symptom improvement at 1 year in those who reduced/stopped cannabis use.

How the study worked

Clinical data on 502 patients with first-episode psychosis were collected from seven London-based Early Intervention in psychosis teams using the MiData audit database. Patients were assessed at entry and after one year using the PANSS (Positive and Negative Syndrome Scale), Young Mania Rating Scale, and Global Assessment of Functioning. Cannabis and other drug use in the preceding 6 months was recorded at both time points.

What this study cannot tell us

This was a naturalistic observational study, not a randomized trial. Patients who reduced cannabis may have differed from continued users in motivation, disease severity, or other factors. Cannabis use was self-reported. The specific products, potency, and frequency of use were not detailed.

How to read the evidence

This is a large naturalistic longitudinal study with two assessment points, providing moderate evidence for the benefits of cannabis reduction.

When this study was published

Published in 2014. Cannabis cessation in first-episode psychosis remains a treatment priority in clinical guidelines.

The bigger picture

Cannabis use in first-episode psychosis remains one of the most clinically important modifiable risk factors for poor outcomes. This study adds to the evidence that targeted cannabis cessation interventions for people with first-episode psychosis could significantly improve recovery trajectories.

Questions still open

What interventions are most effective at helping psychosis patients reduce cannabis use? Why were cannabis users more likely to show manic rather than positive psychotic symptoms? Would the benefits of cannabis reduction persist beyond one year?

Common questions

Why did cannabis reducers improve more than people who never used?

This may reflect a "rebound" effect: cannabis was actively suppressing recovery, and removing it allowed a greater improvement trajectory. Alternatively, people who successfully changed their cannabis use may have been more engaged with treatment overall.

Does cannabis cause psychosis or make it worse?

This study suggests cannabis worsens the course of psychosis rather than causing it directly. The association with manic symptoms rather than classic psychotic symptoms (delusions, hallucinations) adds nuance to the relationship.

Read the original research

Cannabis use and first-episode psychosis: relationship with manic and psychotic symptoms, and with age at presentation.

Psychological medicine, 44(3), 499-506

View on PubMed ↗Publisher’s paper ↗

Citation

Stone, J M; Fisher, H L; Major, B; Chisholm, B; Woolley, J; Lawrence, J; Rahaman, N; Joyce, J; Hinton, M; Johnson, S; Young, A H. (2014). Cannabis use and first-episode psychosis: relationship with manic and psychotic symptoms, and with age at presentation.. Psychological medicine, 44(3), 499-506. https://doi.org/10.1017/S0033291713000883