Is the smoking-depression relationship confounded by alcohol consumption? An analysis by gender

There is a well-established relationship between cigarette smoking and depression. The purpose of the current study is to examine whether alcohol use may be a confounder in this relationship, and whether this relationship differs between men and women. As part of a national survey, 14,063 Canadians were interviewed using random-digit dialing and computer-assisted telephone interviewing. Responses to questions on smoking during the past 12 months allowed participants to be classified as never, former, light, mid-level, and heavier smokers. Alcohol use measures included: usual frequency, usual quantity per drinking occasion, heavy episodic drinking (5 or more drinks), and hazardous drinking. Depression was measured as (a) meeting clinical diagnostic criteria for depression (Composite International Diagnostic Interview) and (b) recent depressed affect (Center for Epidemiological Studies of Depression scale). Multinomial logistic regressions indicated that the association between smoking and depression was only slightly reduced and remained significant when drinking status and drinking pattern were controlled for. The relationship between smoking and depression was stronger for women when depression was measured as meeting clinical criteria for depression, with all categories of smoking by women but only mid-level and heavier smoking by men significant related to depression.