title: 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.
abstract: BACKGROUND
  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.
authors.affiliation: Department of Community Health Sciences, Faculty of Medicine, University of Calgary, 3 Floor TRW Building, 3280 Hospital Dr NW, Calgary, AB, Canada. smkhalid@ucalgary.ca
authors.forename: Salma M
authors.initials: SM
authors.lastname: Khaled
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Bulloch
authors.forename: Jeanne V A
authors.initials: JV
authors.lastname: Williams
authors.forename: Dina H
authors.initials: DH
authors.lastname: Lavorato
authors.forename: Scott B
authors.initials: SB
authors.lastname: Patten
mesh_terms: D000293:Adolescent; D000328:Adult; D002170:Canada / Q000453:epidemiology; D002648:Child; D015331:Cohort Studies; D003865:Major Depressive Disorder / Q000150:complications* / Q000523:psychology; D005260:Female; D005500:Follow-Up Studies; D006306:Health Surveys; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D015995:Prevalence; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology / Q000523:psychology*; D013997:Time Factors; D014029:Tobacco Use Disorder / Q000150:complications / Q000453:epidemiology / Q000523:psychology*; D055815:Young Adult