Smoking in schizophrenia: diagnostic specificity, symptom correlates, and illness severity

Cigarette smoking was consistently found to be more prevalent in individuals with schizophrenia than in other psychiatric groups and the general population. These findings have been interpreted as evidence of a specific association between schizophrenia and smoking. However, the supporting data come primarily from cross-sectional studies, which are susceptible to confounding. Our aim was to test specificity of this link longitudinally in an epidemiologic sample.

A cohort of 542 inpatients with psychosis was followed for 10 years after first hospitalization, completing 5 face-to-face interviews. Assessments included ratings of specific symptoms (psychotic, negative, disorganized, and depressive), Global Assessment of Functioning, and a categorical measure of cigarette consumption. All participants were assigned longitudinal consensus diagnoses by study psychiatrists, and 229 were diagnosed with schizophrenia spectrum disorders (SZ).

At baseline, 52.4% of participants were current smokers and 69.3% were lifetime smokers. Smoking rates did not differ among the diagnostic groups (schizophrenia spectrum, major depressive, bipolar, or other psychotic disorder) at any assessment point. Smokers were more severely ill than nonsmokers but did not differ in specific symptoms either cross-sectionally or longitudinally. Among smokers, changes in cigarette consumption were linked only with changes in depression (beta = .16, P < .001).

Rates of smoking were elevated in subjects with schizophrenia but were just as high with other psychotic disorders. Smoking was not associated with psychotic symptoms, but cigarette consumption covaried with depression over time. Given the devastating health consequences of cigarette use, smoking cessation interventions are urgently needed in this population and should specifically address depression.