Effects of Smoking Status on Remission and Metabolic and Cognitive Outcomes in Schizophrenia Patients Treated with Clozapine

Abstract

Background Even though clozapine is the recommended last-resort antipsychotic, many patients fail to respond and show treatment-refractory psychotic symptoms. Smoking has been suggested as a possible risk factor for poor clozapine response, hampering remission and negatively impacting somatic outcomes. Methods Our aim was to test whether smoking status is associated with remission rates and other symptomatic and somatic outcomes. We therefore assessed remission rates according to The Remission in Schizophrenia Working Group (RSWG) criteria, and metabolic and cognitive outcomes among patients with schizophrenia-spectrum disorders treated with clozapine for at least 6 months. For analyses, we grouped our cohort into 3 groups according to clozapine treatment duration (6 months, 2 years, 5 years). Results One hundred five patients were included in our analyses and grouped according to their clozapine treatment duration. In the 6-months analyses, patients who smoked were significantly more likely to be younger of age (p=0.002) despite on average shorter duration of clozapine treatment (p=0.041) and significantly more likely to be treated with mood-stabilizing co-medication (p=0.030) compared to nonsmokers. Remission rates (p=0.490), as well as a set of metabolic and cognitive variables did not differ between the 2 groups. A related pattern could be observed for the 2- and 5-years analyses. Conclusions Smoking behavior among clozapine-treated schizophrenia patients might delineate a cohort with an earlier onset of the disease. Nevertheless, most findings comparing disease-specific and clinical outcomes among smokers and nonsmokers were negative. Further research is needed to identify strategies to overcome insufficient remission rates in this patient group.

Genome-wide association analyses of symptom severity among clozapine-treated patients with schizophrenia spectrum disorder

“…Participants (N=804) came from five independent cohorts: 470 participants were recruited by the Clozapine International (CLOZIN) [32][33][34][35] consortium in the Netherlands, Germany, Austria, and Finland (the current paper describes the first GWA analyses in this cohort); 174 participants were recruited by the Genetic Risk and Outcome of Psychosis (GROUP) consortium in the Netherlands; 80 participants were recruited by the Cooperative Research Centre (CRC) in Australia; 50 participants were recruited by Hacettepe University in Turkey; and 30 participants were recruited by Mental Health Services Rivierduinen in the Netherlands. All studies were approved by their respective local Institutional Review Boards and all participants provided written informed consent prior to participation.…”