Relation between cigarette smoking and cognitive function in euthymic individuals with bipolar disorder.

BACKGROUND: Individuals with bipolar disorder have higher rates of cigarette smoking and cognitive deficits when compared to the general population. Emerging evidence indicates that both smoking and cognitive deficits are associated with more severe illness presentation and course.
METHODS: The data were derived from a study evaluating a novel treatment for cognitive function in bipolar disorder. Smoking status was determined by self-report; cognitive function was evaluated with a comprehensive cognitive battery, which included measures of psychomotor speed, attention, memory, learning and executive function. The relations between smoking status and cognitive measures were evaluated with two independent-samples t-test and multiple regression.
RESULTS: The sample comprised forty-three subjects with bipolar disorder (Type I/II). There were no consistent differences in neuropsychological performance between current smokers (N=16) and non-smokers (N=27) on most tasks. The occurrence of subjective cognitive failures, as measured with the Cognitive Functioning Questionnaire, was non-significantly lower for smokers compared to non-smokers. Lifetime "smoking load" was negatively associated with premorbid intelligence as estimated by the National Adult Reading Test.
CONCLUSION: This pilot study provides preliminary evidence that cigarette smoking may exert a salutary effect on subjective, but not objective, measures of cognitive function in euthymic bipolar patients. A larger sample size evaluating this hypothesis would be less vulnerable to type II error.