title: The predictive value of smoking expectancy and the heritability of its accuracy.
abstract: BACKGROUND
  Among smokers, former smokers, and never-smokers, this study aimed to (a) determine the predictive value of smoking expectancy on future smoking status, and (b) test the relative contribution of genes and environment to a person's ability to accurately predict future smoking status. For smokers, smoking expectancy reflects the intention to continue smoking; for former smokers, it reflects the intention to take up smoking again; and for never-smokers, it reflects the intention to initiate smoking.
  
  
  METHODS
  A longitudinal design was employed in which participants of the Netherlands Twin Register completed 2 consecutive surveys 2 years apart between 1993 and 2011 (3,591 adolescents aged 14-18 years), or between 1993 and 2004 (11,568 adults, aged 18+ years). Smoking expectancy was measured by asking, "Do you think you'll smoke in a year's time?", with answer categories ranging from "certainly not" to "absolutely yes" on a 5-point scale. To determine the predictive value of smoking expectancy, analyses were performed in smokers, former smokers, and never-smokers separately. Data of 2,987 adolescents and 4,911 adult twins were analyzed to estimate heritability. A dichotomous variable reflected the ability to predict future smoking status (correct/incorrect).
  
  
  RESULTS
  Smoking expectancy significantly predicted future smoking status among former smokers and never-smokers. The ability to accurately predict future smoking status was explained by additive genetic factors for 59% of adolescents and 27% of adults, with the remainder being explained by unique environmental factors.
  
  
  CONCLUSIONS
  A single question on smoking expectancy helps predict future smoking status. Variation in how well subjects predict their future smoking behavior is influenced by genetic factors, especially during adolescence.
authors.affiliation: Department of Biological Psychology, VU University, Amsterdam, The Netherlands;
authors.forename: Jorien L
authors.initials: JL
authors.lastname: Treur
authors.forename: Dorret I
authors.initials: DI
authors.lastname: Boomsma
authors.forename: Gitta H
authors.initials: GH
authors.lastname: Lubke
authors.forename: Meike
authors.initials: M
authors.lastname: Bartels
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Vink
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D008957:Models, Genetic; D012907:Smoking / Q000235:genetics* / Q000523:psychology*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic