title: Age of initiating selected health-risk behaviors among high school students in the United States.
abstract: OBJECTIVE
  To estimate and compare the age of initiation of alcohol use, cigarette smoking, sexual intercourse, and marijuana use among female and male students in U.S. high schools.
  
  
  METHODS
  Using data from the 1991 and 1993 national school-based Youth Risk Behavior Surveys, life-table analysis was used to create hypothetical cohorts to estimate age of initiation of selected health-risk behaviors. The sample size was 12,272 in 1991 and 16,296 in 1993, with an overall response rate of 68% in 1991 and 70% in 1993.
  
  
  RESULTS
  Male students initiate each of these behaviors earlier than female students, but the pace of initiation for females accelerates so that by age 15 years the cumulative proportion of male and female students who have initiated these behaviors is similar. For both female and male students, the youngest cohort appears to initiate use of alcohol and sexual intercourse at earlier ages than older cohorts. Similarly, the younger cohorts of female students appear to initiate smoking cigarettes and using marijuana at earlier ages than older cohorts.
  
  
  CONCLUSIONS
  Many high school students are initiating alcohol use, cigarette smoking, sexual intercourse, and marijuana use at early ages. These data suggest a need for intensive intervention programs by middle/junior high school to motivate and prepare students to avoid these behaviors. Clinicians should begin screening and counseling for risk behaviors in early adolescence.
authors.affiliation: Division of Adolescent and School Health, Centers for Disease Control and Prevention, Atlanta, Georgia 30341-3724, USA.
authors.forename: C W
authors.initials: CW
authors.lastname: Warren
authors.forename: L
authors.initials: L
authors.lastname: Kann
authors.forename: M L
authors.initials: ML
authors.lastname: Small
authors.forename: J S
authors.initials: JS
authors.lastname: Santelli
authors.forename: J L
authors.initials: JL
authors.lastname: Collins
authors.forename: L J
authors.initials: LJ
authors.lastname: Kolbe
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D017668:Age of Onset; D000428:Alcohol Drinking / Q000453:epidemiology / Q000523:psychology; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000523:psychology; D012309:Risk-Taking; D012737:Sex Factors; D012725:Sexual Behavior / Q000523:psychology / Q000706:statistics & numerical data; D012907:Smoking / Q000523:psychology; D014481:United States / Q000453:epidemiology