Current (but not ex) cigarette smoking is associated with worse cognitive performances in schizophrenia: results from the FACE-SZ cohort

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.