Cigarette smoking prior to and following index hospitalization
Of the 72 adolescents who provided information about smoking both prior to and following the index hospitalization, 26 (36%) were current smokers (i.e., smoking > 0 PPD within prior 30 days) at the time of index hospitalization. Of the remaining 46 adolescents who were not current smokers at that time, 41 (89%) reported no prior history of regular smoking and 5 (11%) reported a history of regular smoking. On average, adolescents who reported current smoking consumed slightly over one half of a PPD (mean = 0.6 packs, SD = 0.4), had been smoking for two years (SD = 2), and initiated smoking at age 13 (SD = 2). Current smokers differed from current nonsmokers on age and race. As shown in , adolescent smokers were, on average, approximately one year older than nonsmokers, and there was a higher proportion of White adolescents in the current smoker group (p < 0.05).
Demographic and clinical characteristics of the subsample (n = 113) by smoking status in the month prior to index hospitalization
Smoking status changes between the one-month pre-hospitalization period and the 12-month post-hospitalization period were relatively common among the adolescents; 13 (28%) of the 46 adolescents who were current nonsmokers prior to index hospitalization reported at least one month of smoking in the 12 months following hospital discharge, and 8 (31%) of the 26 adolescents who were current smokers prior to index hospitalization reported at least two consecutive months of nonsmoking during the 12 months following discharge. Over the full length of study participation, 13 of the 42 (31%) adolescents who reported smoking at any point during the study indicated that they had abstained from smoking for two consecutive months, with their longest period of smoking abstinence (≥ 2 months) occurring an average of 19 months (SD = 12) after hospitalization.
Of the 41 adults who provided both pre- and post-index hospitalization smoking data, 23 (56%) reported smoking in the 30 days prior to index hospitalization. Of the 18 adults who were not current smokers at that time, 12 (67%) had no history of regular smoking and 6 (33%) reported regular smoking in the past. On average, current smokers reported that they consumed approximately one PPD (mean = 1.1 packs, SD = 0.6), started smoking at age 16 (SD = 3), and smoked for an average of 9 years (SD = 7). In the adult subsample, there were no significant differences between current smokers and nonsmokers on any of the demographic or clinical characteristics we examined (see ).
In terms of smoking status changes, 5 (28%) of the 18 adults who were not current smokers at the time of the index hospitalization reported smoking during the 12-month post-hospitalization period, and 9 (39%) of the 23 adults who were currently smoking at index hospitalization quit for at least two consecutive months during that same time frame. Over the full length of the study, 9 (32%) of the 28 adults who reported smoking at any point during the study quit for at least two consecutive months, with their longest period of smoking abstinence occurring an average of 18 months (SD = 11) following hospitalization.
Relationship between smoking and the course of BD
Among the adolescents, baseline smoking status did not predict post-hospitalization time to recovery [Wald χ2 = 0.31, p = 0.58; hazard ratio (HR) = 1.37, 95% confidence interval (CI): 0.45–4.15]. Similarly, comparison of the mean percentage of weeks with mood syndromes (i.e., scores ≥ 5 on the composite mood rating scale) indicated that adolescent smokers (mean = 21.13, SD = 4.09) did not significantly differ from nonsmokers (mean = 13.67, SD = 2.66) on this indicator of psychiatric status [F(1,68) = 2.71, p = 0.10]. Finally, in the year following the index hospitalization, 20 (28%) of the adolescents were re-hospitalized and 10 (14%) made a suicide attempt. Adolescents who smoked at baseline were no more likely than nonsmokers to report subsequent hospitalization [Wald χ2 = 0.23, p = 0.63; odds ratio (OR) = 1.34, 95% CI: 0.41–4.35] or suicide attempts (Wald χ2 = 0.85, p = 0.36; OR = 2.02, 95% CI: 0.45–9.01). None of these conclusions changed when we used proportion of months of smoking during the 12-month period following index hospitalization instead of baseline smoking status as the indicator of smoking status. Thus, none of the selected measures of the course of BD post-hospitalization showed any significant differences by smoking status among the adolescents.
In the adults, smoking status did not predict time to recovery following hospital discharge (Wald χ2 = 0.08, p = 0.77; HR = 0.89, 95% CI: 0.39–2.03), and smokers (mean = 28.93, SD = 6.96) did not significantly differ from nonsmokers (mean = 22.87, SD = 7.87) on mean percentage of weeks of study participation in which they met full syndromal criteria for depression or mania/hypomania [F(1,39) = 0.33, p = 0.57]. In the year following discharge from the index hospitalization, nine (22%) of the adults were re-hospitalized and one (2%) made a suicide attempt. Adult smokers were at no higher risk of subsequent hospitalization than nonsmokers (Wald χ2 = 0.01, p = 0.97; OR = 0.97, 95% CI: 0.22–4.31). We were unable to evaluate the relationship between smoking and suicide attempts in the adults because there was only one adult participant who made a suicide attempt in the first year following the index hospitalization. Similar to the findings in adolescents, when we substituted proportion of months of smoking for baseline smoking status in the models, the conclusions did not change.
Relationship between smoking and co-occurring AUD/CUD
Nine (13%) of the adolescents met criteria for a CUD during the first 12 months following index hospitalization, and six (8%) met criteria for an AUD. Eight out of nine (89%) CUDs and all of the AUDs observed during this time period in the adolescents were new-onset disorders (i.e., there was no history of these disorders at the time of the index hospitalization). Cigarette smoking at baseline was associated with increased odds of having AUD/CUD during the 12-month period following the index hospitalization among adolescents (Wald χ2 = 5.82, p = 0.02; OR = 16.62, 95% CI: 1.69–163.13). Proportion of months of smoking during the 12 months following index hospitalization was also associated with AUDs/CUDs during this time period in the adolescents (Wald χ2 = 4.92, p = 0.03; OR = 25.25, 95% CI: 1.46–437.63), mirroring the findings using baseline smoking status as a predictor.
In the 12 months following index hospitalization, seven (17%) of the adult participants met criteria for a CUD and 10 (24%) met criteria for an AUD. Five (71%) of the CUDs and six (60%) of the AUDs were new-onset disorders. Baseline smoking status did not predict the presence of an AUD/CUD in the adults (Wald χ2 = 1.06, p = 0.30; OR = 2.00, 95% CI: 0.53–7.49). The follow-up analysis, in which we substituted proportion of months of smoking during the 12-month post-hospitalization period for baseline smoking status, yielded the same conclusion.
Comparison of mood changes in quitters versus continuing smokers
For the adolescents (see ), after controlling for the initial severity of symptoms, time since hospitalization, and whether the adolescent was taking an antipsychotic or mood stabilizer with at least 75% adherence, change scores on the YMRS from pre- to post-quit were not significantly different for continuing smokers (mean = −1.22, SD = 1.00; 95% CI: −3.24 to 0.81) and quitters [mean = −1.91, SD = 1.45; 95% CI: −4.84 to 1.03; F(1,33) = 0.12, p = 0.73)]. Similar results were found for the HDRS, where the adolescent continuing smokers (mean = −0.73, SD = 0.65; 95% CI: −2.06 to 0.59) did not differ significantly from the quitters (mean = 0.33, SD = 0.93; 95% CI: −1.56 to 2.22) on change in depressive symptoms, [F(1,33) = 0.73, p = 0.40].
Comparison of abstainers and continuing smokers
For the adults (see ) there was a strong relationship between quit status and the presence of an AUD or CUD, with only 1 (4.3%) of the 23 quitters having one or both of these SUDs during the pre-quit period versus 9 (31.0%) of the continuing smokers. Because of its redundancy with the quit status variable, then, we did not include it as a covariate in the analyses. Thus, we controlled only for baseline ratings on the YMRS or HDRS and the time since hospitalization. On the YMRS, continuing adult smokers (mean = −0.96, SD = 0.66; 95% CI: −2.29 to 0.37) did not differ from quitters (mean = 0.58, SD = 0.79; 95% CI: −1.01 to 2.18) on mean change in symptoms of mania [F(1,46) = 2.01, p = 0.16]. On the HDRS, there was also no difference between continuing smokers (mean = 0.27, SD = 0.54; 95% CI: −0.81 to 1.35) and quitters (mean = 0.55, SD = 0.64; 95% CI: −0.75 to 1.84) on changes in depressive symptoms [F(1,46) = 0.74, p = 0.75]. Thus, the results of these two analyses indicate that change in mood symptoms following smoking cessation in adult quitters was no different than change in mood symptoms among continuing smokers over a randomly selected period of the same duration.