Studies and meta-analyses investigating the influence of substance use disorder (SUD) (substance abuse or dependence) on psychopathology and neurocognitive function in schizophrenia patients have revealed controversial results. Most studies did only have small samples and did not focus exclusively on first-episode schizophrenia patients.
Method: In a post-hoc analysis of the European First Episode Schizophrenia Trial (EUFEST) psychopathology and cognitive performances of patients with (FE-SUD, N=119, consisting of N=88 patients with persisting SUD at baseline and N=31 patients with previous SUD) and without SUD (FE-non-SUD, N=204) were compared at baseline and 6 months follow-up. Neurocognitive assessment included the Rey Auditory Verbal Learning Test (RAVLT); Trail Making Tests A and B (TMT), Purdue Pegboard and Digit-Symbol Coding.
Results: In total 31.1% of patients reported SUD, and 22.2% of patients used cannabis. There were no significant differences between patients with and without SUD concerning PANSS scores, extrapyramidal motor symptoms or neurocognitive measures except better performance in psychomotor speed (TMT-A, p=0.033, Cohen's d=0.26) in patients with SUD at 6 months follow-up. Interestingly, SUD patients with ongoing substance use at follow-up showed elevated positive symptoms (PANSS positive score, p=0.008, Cohen's d=0.84) compared to those who abstained. PANSS scores at baseline were increased in patients with an onset of SUD before the age of 16 years. In addition we found a correlation between longer duration of cannabis use and higher cognitive performance as well as reduced symptom improvement and more extrapyramidal motor symptoms in patients with higher frequency of cannabis consumption.
Conclusions: FE-SUD and FE-non-SUD show similar psychopathology and neuropsychological performances at baseline and during the first 6 months of antipsychotic treatment.
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