Persistent heavy smoking as risk factor for major depression (MD) incidence--evidence from a longitudinal Canadian cohort of the National Population Health Survey.

BACKGROUND: Reports of bidirectional associations between smoking and major depression (MD) have been interpreted as providing evidence for confounding by shared-vulnerability factors (SV) that predispose individuals to both conditions. If this is true, then smoking cessation may not reduce the risk of MD. From clinical practice and public health perspectives, the long-term outcomes associated with smoking persistence and cessation are potentially important and deserve exploration. To this end, the 12-year risk of MD in persistent heavy smokers and abstainers who were former-heavy smokers with and without adjustment for potential confounders were compared. METHODS: Follow-up data from the National Population Health Survey (NPHS) was used. Multinomial logistic (ML) models were fit to identify potential confounders. Using proportional hazard (PH) models, unadjusted and adjusted hazard ratios (HRs) for MD outcome were estimated for different smoking patterns. RESULTS: The unadjusted HR relating the risk of MD among current-heavy versus former-heavy smokers was 4.3 (95% CI: 2.6-6.9, p < 0.001). Current-heavy smoking predicted onset of MD (HR = 3.1, 95% CI: 1.9-5.2, p < 0.001) even after adjustment for age, sex and stress - the main confounders. However, this was not the case for the never, former-light, and current-light categories. Evidence of decreased risk of MD among former-heavy relative to current-heavy smokers as function of smoking cessation maintenance time was also found. CONCLUSIONS: Contrary to common beliefs about the benefits of smoking for mental health, our results suggest that current-heavy rather than ever-heavy smoking is a major determinant of MD risk and point towards the benefits of smoking cessation maintenance.

Major depression is a risk factor for shorter time to first cigarette irrespective of the number of cigarettes smoked per day: evidence from a National Population Health Survey.

INTRODUCTION: We assessed whether major depression (MD) predicts progression of nicotine dependence (ND) as measured by reduction in the time to first cigarette (TTFC) after waking and the roles of the number of cigarettes smoked per day (CPD) and stress as explanatory variables of this association. METHODS: Ten years of follow-up data from the National Population Health Survey (NPHS) were used. The analyses were based on this nationally representative sample of the Canadian population who were over the age of 12 years in 1996 (n = 13,298). The NPHS included measures of MD and TTFC. Shorter TTFC was defined as TTFC within 5 min of waking. Heavy smoking (HS) was defined by smoking 20 or more CPD. Using proportional hazard models, unadjusted and adjusted hazard ratios (HRs) for shorter TTFC were estimated for those with and without MD. RESULTS: The unadjusted HR for shorter TTFC among those with MD versus those without MD was 3.7 (95% CI: 2.6-5.3, p < .001). MD predicted onset of shorter TTFC even after adjustment for HS and tendency to smoke more under stress (HR: 1.7; 95% CI: 1.1-2.5, p = .02). When TTFC was defined using longer cutoffs (30 and 60 min), HS completely accounted for the effect of MD on TTFC onset. CONCLUSIONS: MD appears to be a risk factor for transition to shorter TTFC independent of effects of HS and the tendency to smoke more under stress. As MD is often modifiable, the above association points toward a preventive opportunity in relation to worsening of ND.

Predictors of the longitudinal course of major depression in a Canadian population sample.

OBJECTIVE: Most psychiatric epidemiologic studies have used cross-sectional methods, resulting in a lack of information about the longitudinal course of depressive disorders. The objective of our study was to describe the longitudinal epidemiology of major depressive episodes (MDEs) in a Canadian sample using data from the National Population Health Survey (NPHS). METHODS: The NPHS started data collection in 1994 and has evaluated past-year MDE using repeat interviews of the same cohort every 2 years since then. In our study, we examined the number of weeks depressed during years when MDEs occurred, the proportion of respondents having MDEs at consecutive cycles, and MDE counts during follow-up. RESULTS: A sizable proportion of MDEs were brief: about one-half of respondents with past-year MDE reported 8 or fewer weeks of depression during that year. Less than 10% reported that they were depressed for the entire year. However, a larger proportion (19.1%) fulfilled criteria for MDE on consecutive interview cycles, suggesting either persistence or rapid recurrence. The mean number of detected MDEs among those with at least 1 detected MDE up to 2006 was 2. Positive family history, evidence of comorbidity, negative cognitive style, stress, pain, and smoking were associated with a more negative course. CONCLUSIONS: The longitudinal course of MDE in the general population is heterogeneous, including a mixture of brief and more protracted MDEs. Many risk factors for MDE are also associated with a negative course, exceptions being (younger) age and sex. These epidemiologic observations may assist with identification of patients requiring more intensive management in clinical practice.

Cigarette smoking, stages of change, and major depression in the Canadian population.

OBJECTIVE: To describe the 12-month prevalence of major depression in relation to smoking status, nicotine dependence levels, commitment to quit, attempts to quit, and maintenance of smoking cessation in the Canadian general population. METHOD: Data from Public Use Microdata File of the Canadian Community Health Survey: Health and Well-Being were used. The Composite International Diagnostic Interview--Short Form (CIDI-SF) for major depression was used to assess depressive disorder status. The survey also included a smoking module. There were 49,249 respondents assessed by the CIDI-SF, of whom 10,236 were administered the smoking module. Analyses used appropriate measures to deal with survey design effects. RESULT: The prevalence of major depression was highest in current smokers, followed by ever smokers, former smokers, and was lowest in the never smokers. This pattern persisted after stratification for age and sex. For quitting, the prevalence of major depression was highest among people who tried to quit, followed by those who considered quitting, those who quit in the past year, and lowest among those who maintained their smoking cessation status for longer than 1 year. The prevalence of depression among those with a high nicotine dependence level, as assessed by the Fagerstrom Tolerance Questionnaire, was about twice that of people with a low nicotine dependence level. CONCLUSION: The strikingly high prevalence of major depression among current smokers who are young, trying to quit, and with high nicotine dependence levels in the general population indicates that further longitudinal exploration of this topic is urgently needed.