Nicotine dependence and symptoms in schizophrenia - Naturalistic study of complex interactions

Background Smoking may have a beneficial effect on either schizophrenic symptoms or antipsychotic side-effects, but studies are hampered by the lack of control of confounding factors. Aims To explore the self-medication hypothesis in a large sample of stable outpatients with schizophrenia. Method Symptoms, assessed with the Positive and Negative Syndrome Scale (PANSS), and number of hospitalisations were compared in 250 out-patients with DSM - IV schizophrenia classified into three categories: highly dependent smokers, mildly dependent smokers and non-smokers. Log-linear analysis was used to control for potential confounding and interacting variables. Results High PANSS total scores and positive symptoms were less frequent in mildly dependent smokers than in nonsmokers or highly dependent smokers. The highly dependent smokers had the worst outcome. Conclusions The data do not generally support the self-medication hypothesis but rather suggest a complex interaction between nicotine dependence and schizophrenic symptoms. Declaration of interest None. Funding detailed in Acknowledgements.