title: What is the evidence for hardening in the cigarette smoking population? Trends in nicotine dependence in the U.S., 2002-2012.
abstract: BACKGROUND
  It is unclear whether declines in cigarette smoking in the U.S. have resulted in a hardened population of "hardcore" smokers. We studied changes in nicotine dependence severity from 2002 to 2012, using data from the National Survey on Drug Use and Health.
  
  
  METHODS
  We used generalized non-linear factor analysis to examine whether individual Nicotine Dependence Syndrome Scale (NDSS) items functioned differently over time, and whether average NDSS scores changed in a sample of 130,637 current smokers. We also examined trends for individual NDSS sub-scales and whether trends were moderated by tobacco consumption and socio-demographic factors.
  
  
  RESULTS
  Consumption levels and dependence severity both declined over the study period. This decline was driven by priority (e.g., avoiding smoke-free locations) and tolerance dimensions of dependence, while drive (e.g., craving and smoking to relieve negative affect) and continuity (e.g., stability) of smoking did not change. Declines for tolerance were greatest among those without serious psychological distress and among middle-aged smokers. Drive and continuity increased among women and low income smokers.
  
  
  CONCLUSIONS
  We did not find evidence of hardening at the population level for smokers in the U.S., 2002-2012. However, there is evidence of hardening when considering drive and continuity-related nicotine dependence among women and low-income smokers, suggesting these sub-groups are experiencing greater severity of craving, smoking to relieve negative affect, and regularity of smoking despite reduced consumption.
authors: Department of Psychiatry, Yale University, 2 Church Street South, Suite 109, New Haven, CT 06519, United States; Women's Health Research at Yale, United States. Electronic address: philip.h.smith@yale.edu.
authors: Philip H
authors: PH
authors: Smith
authors: Department of Psychology, Wesleyan University, 207 High Street, Middletown, CT 06459, United States.
authors: Jennifer S
authors: JS
authors: Rose
authors: Department of Psychiatry, Yale University, 2 Church Street South, Suite 109, New Haven, CT 06519, United States; Women's Health Research at Yale, United States.
authors: Carolyn M
authors: CM
authors: Mazure
authors: Community Health and Health Behavior, University at Buffalo, SUNY, Buffalo, NY 14214, United States.
authors: Gary A
authors: GA
authors: Giovino
authors: Department of Psychiatry, Yale University, 2 Church Street South, Suite 109, New Haven, CT 06519, United States; Women's Health Research at Yale, United States.
authors: Sherry A
authors: SA
authors: McKee
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008875:Middle Aged; D012720:Severity of Illness Index; D012907:Smoking / Q000453:epidemiology / Q000523:psychology / Q000639:trends*; D011795:Surveys and Questionnaires; D014029:Tobacco Use Disorder / Q000175:diagnosis* / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Cigarette; Dependence; Nicotine; Smoking; Trends