Tobacco smoking and bipolar disorder.

BACKGROUND

We sought to determine whether tobacco smoking is associated with bipolar disorder.

METHOD: This case-control study carried out in Alava, in the north of Spain, included patients with a DSM-III-R diagnosis of bipolar disorder type I (N = 51) and a representative sample of the normal population (N = 517). Smoking history of bipolar patients was assessed with the Fagerstrom Test for Nicotine Dependence and was verified by family members of the patients.

RESULTS

The frequencies of ever smoking and current daily smoking were, respectively, 63% (32/51) and 51% (26/51) for the bipolar patients and 45% (235/517) and 33% (169/517) for the control group (respective odds ratios [ORs] and 95% confidence intervals [CIs] were OR = 2.0, 95% CI = 1.1 to 3.8 and OR = 2.1, 95% CI = 1.2 to 4.0). The differences were significant (p = .03 and p = .042, respectively) for bipolar versus control males. Bipolar disorder (in both genders) was also significantly associated (OR = 4.4, 95% CI = 1.7 to 11.9, p = .0015) with heavy smoking (more than 1 pack per day).

CONCLUSION

Despite its small sample size, this study suggests that smoking may be more prevalent in bipolar patients than in the normal population. Since most patients started to smoke before the onset of illness, vulnerability to bipolar illness may make subjects vulnerable to become tobacco smokers.