title: First cannabis use: does onset shift to younger ages? Findings from 1988 to 2003 from the Dutch National School Survey on Substance Use.
abstract: OBJECTIVE
  To investigate the hypothesis that changes in cannabis prevalence among Dutch secondary school students (aged 12-17 years) were paralleled by shifts in the age of first cannabis use.
  
  
  METHODS
  Data were derived from five waves (1988, 1992, 1996, 1999 and 2003) of the Dutch National School Survey on Substance Use, a nationally representative cross-sectional study, with a total of 32,777 respondents.
  
  
  METHODS
  Written questionnaires on cannabis, tobacco, alcohol, other drug use and socio-demographic and behavioural variables were administered in classroom settings.
  
  
  RESULTS
  Survival analysis showed a strong increase in cumulative incidences by age of first cannabis use from 1988 to 1992, a further increase in 1996 and stabilization in 1999, continuing into 2003. From 1992 to 1996, age of onset shifted towards younger ages. Onset peaked at age 15 in 1992 and age 14 in 1996. The proportion of life-time cannabis users starting at age 13 or younger increased from 26% in 1992 to 41% in 1996. The overall trend was similar for boys and girls.
  
  
  CONCLUSIONS
  The study largely confirmed the expectation that the increase in cannabis use from 1988 to 1996 was paralleled by a decrease in the age of first cannabis use. From 1996 to 2003 age of first cannabis use and prevalence stabilized, possibly occasioned by a change in cannabis policy in the mid-1990s.
authors.affiliation: Trimbos Institute (Netherlands Institute of Mental Health and Addiction), 3500 VJ Utrecht, the Netherlands. kmonshouwer@trimbos.nl
authors.forename: Karin
authors.initials: K
authors.lastname: Monshouwer
authors.forename: Filip
authors.initials: F
authors.lastname: Smit
authors.forename: Ron
authors.initials: R
authors.lastname: de Graaf
authors.forename: Jim
authors.initials: J
authors.lastname: van Os
authors.forename: Wilma
authors.initials: W
authors.lastname: Vollebergh
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D017668:Age of Onset; D002648:Child; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology*; D008385:Marijuana Smoking / Q000453:epidemiology*; D009426:Netherlands / Q000453:epidemiology; D015995:Prevalence; D013334:Students; D011795:Surveys and Questionnaires