title: A longitudinal examination of alcohol, marijuana, and cigarette perceived norms among middle school adolescents.
abstract: BACKGROUND
  Adolescents tend to overestimate the prevalence of substance use among their peers and these perceived norms are associated with their current and future use. However, little is known about how perceived norms change over time during middle school, a developmental period when adolescents are at-risk for initiating substance use.
  
  
  METHODS
  We examined changes in perceived norms of alcohol, marijuana, and cigarettes over a two-year period among a large and diverse sample of 6th and 7th grade youth (N=6097; 50.1% female; 54% Hispanic). Participants completed a baseline survey and two subsequent annual surveys. Participants estimated the percentage of their peers they believed used each substance, as well as indicated levels of personal use, offers to use from peers, and exposure to peers who were using each substance.
  
  
  RESULTS
  Perceived norms of all three substances increased over time. Increases were somewhat attenuated when controlling for demographic factors, personal use, and peer factors, but remained significant. Female adolescents and those reporting non-Hispanic White ethnicity experienced the greatest increase in perceived norms over time.
  
  
  CONCLUSIONS
  Normative perceptions of substance use increase greatly during the middle school years, an effect which cannot be fully explained by demographics, personal use, or peer factors. Given that perceived norms are often associated with personal use, early interventions with middle school youth are warranted to prevent the growth of these influential factors during this developmental period.
authors.affiliation: RAND Corporation, 1776 Main Street, PO Box 2138, Santa Monica, CA 90407, United States. Electronic address: ericp@rand.org.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Pedersen
authors.forename: Jeremy N V
authors.initials: JN
authors.lastname: Miles
authors.forename: Brett A
authors.initials: BA
authors.lastname: Ewing
authors.forename: Regina A
authors.initials: RA
authors.lastname: Shih
authors.forename: Joan S
authors.initials: JS
authors.lastname: Tucker
authors.forename: Elizabeth J
authors.initials: EJ
authors.lastname: D'Amico
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000428:Alcohol Drinking / Q000523:psychology*; D001290:Attitude; D002140:California / Q000453:epidemiology; D002648:Child; D005006:Ethnicity; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008385:Marijuana Smoking / Q000523:psychology*; D010379:Peer Group; D012016:Reference Values; D012737:Sex Factors; D012907:Smoking / Q000523:psychology*; D012959:Socioeconomic Factors
keywords: Adolescents; Alcohol; Cigarettes; Marijuana; Perceived norms