Patients with first-episode psychosis who use synthetic cannabinoids (SPICE) experience more severe and persistent positive symptoms and less improvement in aberrant salience—the tendency to assign excessive meaning to neutral stimuli—compared with natural cannabis users and non-users. Non-users show better recovery in global functioning. Aberrant salience scores decline over six months in all groups, but SPICE-users start higher and improve less. Negative symptoms are most prominent among non-users. These findings may help clinicians tailor diagnosis and treatment for substance-induced versus non-substance-related psychosis.
First-episode psychosis patients who also have cannabis use disorder show more severe positive symptoms, dissociative experiences, and worse overall functioning compared with patients who do not use cannabis, even when both groups receive comparable antipsychotic treatment. Over an eight-month follow-up, cannabis users continue to have higher levels of positive symptoms and dissociation, and their global functioning worsens, while functioning improves in non-users. The findings suggest that greater dissociation and positive symptoms at first episode and their persistence may characterize cannabis-associated psychosis and help explain the diverging trajectories in functioning.