title: Current patterns of marijuana use initiation by age among US adolescents and emerging adults: implications for intervention.
abstract: More recent data are required for effective measures to prevent marijuana use among youth in the United States.
  
  
  
  To investigate the risk of marijuana use onset by age using the most recent data from a national sample.
  
  
  
  Data for participants (n = 26,659) aged 12-21 years from the 2013 National Survey on Drug Use and Health (NSDUH) (50.4% male, 55.6% White) were analyzed. Patterns of the risk of marijuana use initiation from birth to age of 20 years by single year of age were characterized using hazards survival models.
  
  
  
  The estimated hazards of marijuana use showed unique age patterns for the overall sample and by gender and racial/ethnic groups. Up to age of 11 years, the hazards of marijuana use initiation were below 0.0500; the hazards after age of 11 years increased rapidly with two peaks at age 16 (0.1291) and 18 years (0.1496), separated by a reduction at age 17 years (0.1112). The age pattern differed significantly by gender (hazards from high to low: male, female) and race/ethnicity (hazards from high to low: multi-racial, Black, White, Hispanic, and Asian). By age of 21 years, 54.1% (56.4% for male and 51.9% for female) had initiated marijuana use with a mean onset age of 16.5 years.
  
  
  
  This study documented the risk of marijuana use initiation by age. Research findings suggest the timing of marijuana use prevention was no later than middle school. Additional attention is indicated to multi-racial/ethnic youth. Future interventions should be developed for both parents and adolescents, and delivered to the right target population at the right time.
authors.affiliation: a Department of Epidemiology , College of Public Health and Health Professions, College of Medicine, University of Florida , Gainesville , FL , USA.
authors.forename: Xinguang
authors.initials: X
authors.lastname: Chen
authors.affiliation: a Department of Epidemiology , College of Public Health and Health Professions, College of Medicine, University of Florida , Gainesville , FL , USA.
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.affiliation: a Department of Epidemiology , College of Public Health and Health Professions, College of Medicine, University of Florida , Gainesville , FL , USA.
authors.forename: Sonam O
authors.initials: SO
authors.lastname: Lasopa
authors.affiliation: a Department of Epidemiology , College of Public Health and Health Professions, College of Medicine, University of Florida , Gainesville , FL , USA.
authors.forename: Linda B
authors.initials: LB
authors.lastname: Cottler
mesh_terms: D000293:Adolescent; D000367:Age Factors; D017668:Age of Onset; D002648:Child; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology* / Q000208:ethnology / Q000517:prevention & control; D044469:Racial Groups / Q000706:statistics & numerical data*; D012737:Sex Factors; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Hazards; adolescents; initiation of marijuana use; racial/ethnic differences