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Background Tobacco use is common in subjects with schizophrenia (SZ) and has sometimes been associated with better functioning in short-term studies. Only few studies embrace an extensive examination of tobacco influence on clinical, cognitive and therapeutic characteristics in stabilized SZ outpatients. The objective of the present study was to assess the association between cognitive performances and smoking status in SZ subjects. Methods In total, 1233 SZ participants (73.9% men, mean age 31.5) were included and tested with a comprehensive battery. Tobacco status was self-declared (never-, ex-, or current smokers). Multivariable analyses including principal component analyses (PCA) were used. Results In total, 53.7% were smokers with 33.7% of them nicotine-dependent. Multiple factor analysis revealed that current tobacco smoking was associated with impaired general intellectual ability and abstract reasoning (aOR 0.60, 95% IC 0.41–0.88, p = 0.01) and with a lifetime alcohol use disorder (p = 0.026) and a lifetime cannabis use disorder (p < 0.001). Ex- and never-smokers differed for age, mean outcome, cannabis history and medication [ex-smokers being older (p = 0.047), likely to have higher income (p = 0.026), a lifetime cannabis use disorder (p < 0.001) and higher CPZeq doses (p = 0.005)]. Premorbid IQ in the three groups significantly differed with, from higher to lower: ex-smokers, never-smoker, current smokers (all p < 0.001). Conclusions This study is the largest to date providing strong evidence that chronic smoking is associated with cognitive impairment in SZ, arguing against the self-medication hypothesis as a contributor to the high prevalence of smoking in SZ. Ex-smokers may also represent a specific subgroup. Longitudinal studies are warranted to determine the developmental impact of tobacco on neurocognition.

Schizophrenia is characterized by the most salient medication adherence problems among severe mental disorders, but limited prospective data are available to predict and improve adherence in this population. This investigation aims to identify predictors of medication adherence over a one-year period in a large national cohort using clustering analysis. Outpatients were recruited from ten Schizophrenia Expert Centers and were evaluated with a day-long standardized battery including clinician and patient-rated medication adherence measures. A two-step cluster analysis and multivariate logistic regression were conducted to identify medication adherence profiles based on the Medication Adherence rating Scale (MARS) and baseline predictors. A total of 485 participants were included in the study and medication adherence was significantly improved at the one-year follow-up. Higher depressive scores, lower insight, history of suicide attempt, younger age and alcohol use disorder were all associated with poorer adherence at one year. Among the 203 patients with initially poor adherence, 86 (42%) switched to good adherence at the one-year follow-up, whereas 117 patients (58%) remained poorly adherent. Targeting younger patients with low insight, history of suicide, alcohol use disorder and depressive disorders should be prioritized through literacy and educational therapy programs. Adherence is a construct that can vary considerably from year to year in schizophrenia, and therefore may be amenable to interventions for its improvement. However, caution is also warranted as nearly one in five patients with initially good adherence experienced worsened adherence one year later.