title: Disentangling two underlying processes in the initial phase of substance use: Onset and frequency of use in adolescent smoking.
abstract: OBJECTIVE
  Most studies on adolescent smoking focus either on the probability of smoking onset or frequency of smoking. We assume the existence of two different qualitatively distinct processes in smoking acquisition. Therefore our objective was to test a two-part latent growth model, which assumes that psychosocial variables associated with the probability of smoking onset are different from, or differently related to variables associated with frequency of smoking given smoking onset.
  
  
  METHODS
  The predictive associations of blocks of variables of (1) intrapersonal factors, (2) cognitions, (3) role models, and (4) family variables, on both smoking onset, and frequency of smoking given smoking onset, were tested in a nationwide sample of Dutch adolescents by using a two-part model.
  
  
  CONCLUSIONS
  Smoking onset was instigated by a variety of factors, while similar and other factors predicted frequency of smoking given smoking onset itself. Self-esteem, attitudes, and proportion of friends smoking, were identified as factors that affected both absolute smoking and frequency of smoking.
  
  
  CONCLUSIONS
  This study illustrates that it makes sense to differentiate between smoking onset and frequency of smoking and that few factors are active in both processes.
authors.affiliation: Behavioural Science Institute, Radboud University Nijmegen, The Netherlands. R.otten@bsi.ru.nl
authors.forename: Roy
authors.initials: R
authors.lastname: Otten
authors.forename: Pol A C
authors.initials: PA
authors.lastname: van Lier
authors.forename: Rutger C M E
authors.initials: RC
authors.lastname: Engels
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008960:Models, Psychological; D009426:Netherlands / Q000453:epidemiology; D010287:Parent-Child Relations; D010379:Peer Group; D012307:Risk Factors; D012649:Self Concept; D020377:Self Efficacy; D012907:Smoking / Q000453:epidemiology / Q000523:psychology