Tobacco smoking in treatment-resistant schizophrenia patients is associated with impaired cognitive functioning, more severe negative symptoms, and poorer social adjustment

Tobacco smoking is common in schizophrenia patients. It has been reported that schizophrenia patients who are tobacco smokers have better cognitive performances compared to those who are nonsmokers. However, little is known on the effects of tobacco smoking in treatment-resistant schizophrenia (TRS) patients. The aim of this study was to compare cognitive performances, psychotic symptoms, and social adjustment in tobacco smoker TRS patients compared to nonsmoker TRS patients. Smoker and nonsmoker TRS patients did not differ in demographics and in mean daily antipsychotic dose. Smoker TRS patients had significantly higher scores than nonsmoker patients on the positive and negative syndrome scale (PANSS) and on the negative symptoms subscale. These patients also performed worse than nonsmoker patients on problem-solving cognitive domain. Social adjustment was not significantly different between the two groups. In both groups of patients, worse cognitive performances were mostly predicted by higher severity of negative symptoms. Worse performances on the verbal memory and problem-solving cognitive domains were correlated with social-functioning impairment in tobacco smoker TRS patients but not in nonsmoker ones. The results showed that tobacco smoking was not significantly associated with better cognitive performances in TRS patients, while it was significantly associated with higher negative symptoms. Even if a direct causative mechanism cannot be inferred and despite the fact that these patients may use tobacco to self-medicate, it could be speculated that these associations may, at least partially, be related to a tobacco-smoking-induced worsening of abnormal dopamine dysfunction, which has been suggested to occur in TRS patients.