Adding cannabis to tobacco before first psychosis was linked to earlier onset and more severe symptoms | Research

The takeaway

Among 284 first-episode psychosis patients, those who used both tobacco and cannabis before onset had earlier first symptoms (age 23.7 vs. 26.2) and more perceptual abnormalities, hallucinations, and disorganized thinking than tobacco-only users.

Psychiatrists treating first-episode psychosis, psychosis prevention researchers, substance use clinicians

Cannabis+tobacco users had psychosis onset 2.5 years earlier than tobacco-only users

What the researchers found

FEP patients with prior tobacco-only use (n=56) had more sleep disturbances (42.9% vs. 18.8%) and less social withdrawal (33.9% vs. 58%) than those with no substance use (n=70). Those with combined tobacco and cannabis use (n=144) had higher rates of ideas of reference, perceptual abnormalities, hallucinations, and disorganized thinking than tobacco-only users, plus earlier age at first symptom (23.7 vs. 26.2 years).

Why it matters

Tobacco use alone was not associated with earlier psychosis onset, but adding cannabis was. This helps disentangle the roles of tobacco and cannabis in psychosis risk, suggesting cannabis is the key driver of earlier and more severe first episodes.

The numbers in context

284 FEP patients, 231 controls; tobacco+cannabis group (n=144): age at first symptom 23.7 years; tobacco-only (n=56): 26.2 years (p=0.011); tobacco+cannabis had higher rates of hallucinations (55.4% vs 71.5%), perceptual abnormalities (46.4% vs 67.4%), disorganized thinking (41.1% vs 61.1%)

How the study worked

Retrospective analysis from the Spanish PEPs longitudinal study of 284 FEP patients and 231 matched healthy controls. First psychotic experiences assessed with the Symptom Onset in Schizophrenia Inventory. Compared substance use groups: no use, tobacco only, and tobacco plus cannabis.

What this study cannot tell us

Retrospective substance use recall. Cross-sectional comparisons at study entry. Spanish sample may not generalize. Cannot determine if substance use caused psychosis or shared risk factors produced both. Unequal group sizes.

How to read the evidence

Well-characterized FEP cohort with matched controls, though retrospective substance use reporting and cross-sectional analysis limit causal inference.

When this study was published

Published in 2021.

The bigger picture

Since most cannabis users also smoke tobacco, separating their effects on psychosis is challenging. This study suggests tobacco alone produces a distinct, milder clinical profile, while the addition of cannabis drives the stereotypical earlier-onset, more severe psychosis pattern.

Questions still open

Would the tobacco-only psychosis subgroup have a different treatment response or prognosis? Does the sleep disturbance pattern in tobacco-only users suggest a different neurobiological pathway?

Common questions

Does tobacco cause psychosis?

Tobacco alone was not associated with earlier psychosis onset. Tobacco-only users actually had fewer psychotic symptoms (fewer hallucinations, less disorganized thinking) than those who also used cannabis. However, they did have more sleep disturbances.

What changed when cannabis was added?

Adding cannabis to tobacco was associated with psychosis onset about 2.5 years earlier (age 23.7 vs. 26.2) and significantly higher rates of ideas of reference, perceptual abnormalities, hallucinations, and disorganized thinking.

Read the original research

Impact of previous tobacco use with or without cannabis on first psychotic experiences in patients with first-episode psychosis.

Schizophrenia research, 236, 19-28

View on PubMed ↗Publisher’s paper ↗

Citation

González-Blanco, Leticia; García-Portilla, María Paz; Gutiérrez, Miguel; Mezquida, Gisela; Cuesta, Manuel J; Urbiola, Elena; Amoretti, Silvia; Barcones, Fe; González-Pinto, Ana; Pina-Camacho, Laura; Corripio, Iluminada; Vieta, Eduard; Baeza, Immaculada; Toll, Alba; Sáiz, Pilar A; Bobes, Julio; Bernardo, Miguel. (2021). Impact of previous tobacco use with or without cannabis on first psychotic experiences in patients with first-episode psychosis.. Schizophrenia research, 236, 19-28. https://doi.org/10.1016/j.schres.2021.07.017