Recent Cannabis Use Doesn't Worsen Brain Wave Abnormalities in Psychosis | Research

The takeaway

EEG analysis of 93 psychosis patients found no difference in brain activity abnormalities between recent cannabis users and non-users, suggesting these alterations are core features of psychosis itself.

Psychosis researchers, psychiatric clinicians, neuroscience-interested cannabis researchers

No EEG differences between cannabis-using and non-using psychosis patients

What the researchers found

Both cannabis-using and non-using psychosis patients showed impaired spectral entropy modulation and elevated connectivity strength compared to 86 healthy controls. Crucially, no significant differences were found between the two patient groups on any EEG measure, suggesting cannabis was not driving the abnormalities.

Why it matters

If cannabis drove the brain activity abnormalities seen in psychosis, treatment strategies would differ. Finding that these are intrinsic to psychosis suggests they are vulnerability markers rather than substance-induced artifacts.

The numbers in context

93 psychosis patients (32 recent cannabis users, 61 non-users) and 86 healthy controls. Both patient groups showed impaired SE modulation and elevated gamma/broadband connectivity. No between-patient-group differences on any measure.

How the study worked

EEG study during a P300 task comparing 93 psychosis patients (32 recent cannabis users, 61 non-users) with 86 healthy controls, measuring spectral entropy modulation and connectivity strength in theta, broadband, and gamma bands.

What this study cannot tell us

Cross-sectional design captures only recent cannabis use (past week). Does not address long-term or early-onset cannabis effects. Cannabis potency, frequency, and age of onset not considered. Schizophrenia and bipolar patients grouped together.

How to read the evidence

Well-powered EEG study with healthy controls, but cross-sectional design and focus on recent use only limits broader conclusions.

When this study was published

2025 EEG study examining the cannabis-psychosis brain activity relationship.

The bigger picture

Cannabis use is extremely common in psychosis, and clinicians often attribute cognitive and brain changes to cannabis. This study suggests some of those changes are inherent to the psychotic process, which has implications for both treatment and prognosis.

Questions still open

Do long-term cannabis effects on brain activity differ from recent use effects? Could early-onset cannabis use contribute to developing these brain abnormalities initially? Do specific EEG patterns predict psychosis outcomes?

Common questions

Does cannabis cause the brain changes seen in psychosis?

This study found the same brain activity abnormalities in psychosis patients regardless of whether they had recently used cannabis, suggesting these changes are core features of the disease rather than cannabis-induced effects.

Should psychosis patients stop using cannabis?

While this study found recent cannabis use did not worsen specific EEG abnormalities, it only looked at one set of brain measures. Other research has shown cannabis can worsen psychotic symptoms and outcomes, so the broader clinical picture is still important.

Read the original research

Influence of recent cannabis use on altered spectral entropy modulation and connectivity strength in patients with psychosis.

European archives of psychiatry and clinical neuroscience

View on PubMed ↗Publisher’s paper ↗

Citation

Molina, Vicente; Díez, Álvaro; Fernández-Linsenbarth, Inés; Osorio-Iriarte, Emma; Beño-Ruiz de la Sierra, Rosa; Martín-Santiago, Oscar; Rodríguez-Valbuena, Claudia; Fiorini-Talavera, Juan Carlos; Arjona, Antonio. (2025). Influence of recent cannabis use on altered spectral entropy modulation and connectivity strength in patients with psychosis.. European archives of psychiatry and clinical neuroscience. https://doi.org/10.1007/s00406-025-02004-0