A prospective study of the impact of smoking on outcomes in bipolar and schizoaffective disorder
Introduction
The prevalence of smoking in psychiatric illness is greater than that observed in the general community. A study of psychiatric outpatients (N = 2774) in the United States found that the prevalence of smoking was highest for schizoaffective disorder (67%), followed by bipolar disorder (66%), which was greater than schizophrenia (63%) and all patients (61%), and was higher than the prevalence of smoking in the general population (24%) [1]. In a study of 424 patients, Diaz et al [2] found that the prevalence of current daily smoking was 57% for major depression (n = 67), 66% for bipolar disorder (n = 99), and 74% for schizophrenia (n = 258), compared with 25% in a cohort of volunteer controls (n = 402). In the 2004-2005 National Health Survey in Australia, 32% of adults self-reporting mental or behavioral problems were current daily smokers compared with 20% of adults without mental or behavioral problems [3]. Figures from the National Drug Strategy Household Survey suggested that in 2007, 22.1% of Australian men and 18% of women aged 20+ years were current smokers. Prevalence was greatest in the 25- to 29-year-old-age stratum, 29.3% being men and 26.7% being women, and lowest in the 70-year-or-older-age stratum, 8.1% being men and 6.0% being women [4].
Cross-sectional studies suggest an association between worse course and outcomes of bipolar disorder and schizoaffective disorder with tobacco use. In the Systematic Treatment Enhancement Program, tobacco use was associated with greater rapid cycling, comorbid psychiatric disorders, substance use, being currently episodic, more lifetime depressive and manic episodes, and greater episode severity [5]. Smoking may also adversely impact treatment response. Berk et al [6] compared smokers with nonsmokers in pooled data from 3 large clinical trials examining olanzapine treatment of acute mania and found that smoking was associated with worse treatment outcomes on the Young Mania Rating Scale (YMRS; P = .002) and the Clinical Global Impressions scale for bipolar disorder (CGI-BP; P < .001). The rate of suicide attempts in smokers (49%) was greater than in that in nonsmokers (25%) with bipolar disorder [7].
Association have been identified between tobacco smoking in bipolar disorder and risks to physical health. In a study comparing people with serious mental illness (N = 46 136) with controls (N = 300 426), Osborn et al [8] found a significant association between mental illness and chronic heart disease, explained in part, but not entirely, by tobacco smoking. Birkenaes et al [9] investigated cardiovascular risk factors in people in Olso with bipolar disorder (N = 110) and found that 55 (50%) smoked daily and 25 (22.6%) had a body mass index of 30 kg/m2 or higher. Gonzalez-Pinto et al [10] found that alcohol abuse or dependence was more prevalent in bipolar patient who smoke or used to smoke compared with those who have never smoked (P = .0012).
To clarify the potential role of reverse causality, prospective studies are required to define the impact of an exposure variable on outcome. To our knowledge, there have been no prospective studies that relate smoking to mental health outcomes for people experiencing bipolar disorder. The aim of this study was therefore to prospectively investigate the effect of tobacco use on the course and outcomes of bipolar disorder and schizoaffective disorder in a 24-month, longitudinal, observational study. The hypothesis of the study was that smoking status at baseline would predict poorer scores in mental health and quality-of-life rating scales in participants who smoke daily compared with those who do not.
Section snippets
Method
The Bipolar Comprehensive Outcomes Study (BCOS) is a 2-year, prospective, noninterventional observational study of 239 participants with a diagnosis of either bipolar I disorder (n = 175) or schizoaffective disorder, bipolar type (n = 64). Full details of the study methodology have been published elsewhere [11], [12]. The studies aims were to investigate clinical, functional, and economic outcomes associated with naturalistic treatment. Data on tobacco smoking were collected; however, assessing
Results
One participant withdrew consent. Data from the 239 remaining participants were analyzed; 122 (51%) participants who smoked daily were compared with 117 (49%) participants who did not. The nondaily smokers group (nonsmokers) consisted of 55 (23%) participants who never smoked, 8 (3.4%) who were occasional smokers, 51 (21.3%) who were ex-smokers, and 3 (1.3%) who experimented a few times but were never regular smokers. Data were obtained using the Habits form administered at baseline. This form
Discussion
High rates of smoking were reported in this cohort, with 51% smoking daily and 54.4% being current smokers (daily + occasional smokers). This is in counterpoint to the 23% local rates of tobacco smoking for adults in Australia (26% men; 20% women) [15] and is concordant with the literature showing that the prevalence of smoking is higher in this cohort than in the general population. In this study, daily smokers experiencing bipolar and schizoaffective disorder had significantly worse outcomes
Acknowledgment
This study was supported by funding from Eli Lilly.
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