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.

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.

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).

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.

The determinants of quality of life (QoL) in schizophrenia are largely debated, mainly due to methodological discrepancies and divergence about the concepts concerned. As most studies have investigated bi- or tri-variate models, a multivariate model accounting for simultaneous potential mediations is necessary to have a comprehensive view of the determinants of QOL. We sought to estimate the associations between cognitive reserve, cognition, functioning, insight, depression, schizophrenic symptoms, and QoL in schizophrenia and their potential mediation relationships.

We used structural equation modeling with mediation analyses to test a model based on existing literature in a sample of 776 patients with schizophrenia from the FondaMental Foundation FACE-SZ cohort.

Our model showed a good fit to the data. We found better functioning to be positively associated with a better QoL, whereas better cognition, better insight, higher levels of depression, and schizophrenic symptoms were associated with a lower QoL in our sample. Cognitive reserve is not directly linked to QoL, but indirectly in a negative manner via cognition. We confirm the negative relationship between cognition and subjective QoL which was previously evidenced by other studies; moreover, this relationship seems to be robust as it survived in our multivariate model. It was not explained by insight as some suggested, thus the mechanism at stake remains to be explained.

The pathways to subjective QoL in schizophrenia are complex and the determinants largely influence each other. Longitudinal studies are warranted to confirm these cross-sectional findings.