The overall prevalence of current smoking was 61% and of heavy smoking, was 18%. Current smokers reported consuming an average of 21.6 cigarettes per day (SD = 14.4). Seventy one percent of current smokers reported smoking 10 or more cigarettes per day.
The demographic characteristics of smokers and heavy smokers are shown in . Current smoking was more common among male respondents and among those in the middle age categories (30–46 years old) relative to patients under the age of 30 or over the age of 46. No other demographic differences emerged in comparisons of smokers vs. non-smokers. Heavy smokers were more likely to be male, older, and Caucasian. Marital status was unrelated to current smoking habits.
Percentage of Psychiatric Outpatients who are Current Smokers and Heavy Smokers, by Demographic Characteristics, Psychiatric Diagnosis, Psychopathology Level, and Risk for Substance Abuse (N = 2774)
Smoking Status as Function of Risk for Substance Use Disorders and Caffeine Consumption
Twenty-one percent of participants (n = 568) were at risk for alcohol dependence based on AUDIT scores, and 13% (n = 359) were at risk for drug dependence based on their score on the DAST. A total of 8% (n = 217) were at elevated risk for both alcohol and drug dependence. Bivariate associations between smoking status and substance use variables are shown in . As predicted, patients at elevated risk for alcohol and drug dependence reported higher rates of current smoking (78% and 83%, respectively) compared to those classified as low risk (56% and 58%; see ). Similarly, patients with elevated AUDIT scores reported higher rates of heavy smoking (22%) compared to those with low AUDIT scores (18%). Rates of heavy smoking did not differ as a function of risk for drug dependence based on the DAST. Among patients at elevated risk for both drug and alcohol dependence (not tabled), 84% reported current smoking compared to 59% among other respondents, χ2 (1) = 54.79, p < .0001.
A large majority (86%) reported consumption of beverages likely to contain caffeine (M = 3.64 servings per day; SD = 5.96). Daily caffeine consumption was strongly related to current smoking status, with 81% of patients reporting heavy caffeine consumption being classified as current smokers compared to 46% among light caffeine users (see ). Similarly, those reporting heavy caffeine use were much more likely to be heavy smokers (40%) compared to those reporting moderate (20%) and light (9%) caffeine intake.
Psychiatric Characteristics of Smokers versus Non-Smokers
Bivariate analyses revealed significant differences in smoking rates as a function of diagnostic classification (see ). Patients with schizoaffective disorder reported the highest smoking rates (67%), followed by patients with bipolar disorder (66%), schizophrenia (63%), “other” (61%), depression (60%), anxiety disorders (56%), and adjustment disorders (51%). Subgroup analyses revealed that patients with schizoaffective disorder reported higher smoking rates (67%) compared to all other diagnostic subgroups combined (60%), χ2 (1) = 5.20, p < .03, and patients with an adjustment disorder were significantly less likely to report current smoking compared to all other diagnostic groups combined (51% vs 62%, χ2 (1) = 11.80, p < .005).
Diagnostic differences also emerged for analyses of heavy smoking (see ). Patients with schizoaffective disorder reported the highest rate of heavy smoking (27%), followed by patients with bipolar disorder (22%) and schizophrenia (22%). Rates of heavy smoking ranged from 13% to 16% among patients with adjustment disorders, depression, anxiety disorders, or “other” diagnoses. Follow-up comparisons indicated that a higher percentage of patients with schizoaffective disorder (27% vs 17%, χ2 (1) = 15.23, p < .0001), and schizophrenia (22% vs 17%, χ2 (1) = 8.26, p < .005), reported heavy smoking compared to other diagnostic subgroups combined. A lower percentage of patients with depression (14% vs 20%, χ2 (1) = 11.51, p < .005), and adjustment disorder (13% vs 19%, χ2 (1) = 7.05, p < .01), reported heavy smoking compared to other diagnostic subgroups combined.
In terms of illness severity, 38% (n = 1060) were classified as receiving care from a clinic serving more severely impaired patients. Significant bivariate associations between illness severity and smoking status were observed, indicating higher smoking levels among patients receiving care from clinics serving more severely impaired patients. Rates of current and heavy smoking were 65% and 22% respectively among patients classified as “higher severity,” compared to rates of 58% and 16% among “lower severity” patients.
Although psychiatric diagnosis, illness severity, and substance use were all significantly associated with smoking status, bivariate analyses do not adjust for collinearity across predictor variables. To characterize the independent contributions of patient diagnosis, illness severity, and substance use as predictors of smoking status, two multivariate logistic regression analyses were conducted in which all predictor variables were entered simultaneously. The pattern of findings was largely consistent with that which was observed in the bivariate analyses. As shown in , risk for drug and alcohol dependence, as well as current caffeine consumption were all independent predictors of current smoking in the multivariate model. With adjustment disorder as the reference group, all diagnoses except “other” emerged as significant correlates of current smoking. Finally, the multivariate analysis showed that illness severity was a predictor of current smoking at trend level (p < .06), with patients in the high severity group being at increased risk for smoking relative to those in the lower severity group.
Multivariate Logistic Regression Analyses Predicting Current and Heavy Smoker Status (N = 2774)
However, analyses to determine whether risk factors for current smoking varied across different patient subgroups revealed that the main effects for diagnosis and illness severity were qualified by a significant diagnosis-by-illness severity interaction that contributed to the prediction of smoking beyond that which was explained by all main effects (Δ Model χ2 = 20.68, p < .005). To evaluate this interaction, we conducted separate logistic regression analyses for patients in the low versus high illness severity group. Psychiatric diagnosis was not a significant risk factor for smoking among patients in the low illness severity subgroup. Among patients in the high illness severity group, diagnoses of schizoaffective disorder, bipolar disorder, and schizophrenia emerged as significant risk factors for smoking relative to other diagnoses (Wald χ2 = 10.48, AOR = 1.61, CI = 1.21 – 2.14, p < .005). This interaction is illustrated in , which shows smoking rates as a function of illness severity and diagnosis. There were no other significant two-way interactions for analyses of current smoking status.
Smoking Status as a Function of Psychiatric Diagnosis and Illness Severity Classification
also shows multivariate predictors of heavy smoking. Caffeine use remained a strong predictor of heavy smoking in the multivariate model, but the other substance use variables did not contribute to the prediction of heavy smoking. Psychiatric diagnosis also was independently associated with heavy smoking. With adjustment disorder as the reference group, patients with schizoaffective disorder, bipolar disorder, or schizophrenia were more likely to report heavy smoking. Neither the illness severity indicator nor the diagnosis-by-illness severity interaction predicted heavy smoking, and no other significant interactions emerged in multivariate analyses.