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

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).

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.

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.

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.

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.