title: Using cross-classified multilevel models to disentangle school and neighborhood effects: an example focusing on smoking behaviors among adolescents in the United States.
abstract: BACKGROUND
  Despite much interest in understanding the influence of contexts on health, most research has focused on one context at a time, ignoring the reality that individuals have simultaneous memberships in multiple settings.
  
  
  METHODS
  Using the example of smoking behavior among adolescents in the National Longitudinal Study of Adolescent Health, we applied cross-classified multilevel modeling (CCMM) to examine fixed and random effects for schools and neighborhoods. We compared the CCMM results with those obtained from a traditional multilevel model (MLM) focused on either the school and neighborhood separately.
  
  
  RESULTS
  In the MLMs, 5.2% of the variation in smoking was due to differences between neighborhoods (when schools were ignored) and 6.3% of the variation in smoking was due to differences between schools (when neighborhoods were ignored). However in the CCMM examining neighborhood and school variation simultaneously, the neighborhood-level variation was reduced to 0.4%.
  
  
  CONCLUSIONS
  Results suggest that using MLM, instead of CCMM, could lead to overestimating the importance of certain contexts and could ultimately lead to targeting interventions or policies to the wrong settings.
authors.affiliation: Psychiatric and Neurodevelopmental Genetics Unit, Center for Human Genetic Research, Massachusetts General Hospital, 185 Cambridge St, Simches Research Building, 6th Floor, Boston, MA 02114, USA; Department of Psychiatry, Harvard Medical School, Boston, MA 02115, USA; Stanley Center for Psychiatric Research, The Broad Institute, Cambridge, MA 02142, USA. Electronic address: edunn2@mgh.harvard.edu.
authors.forename: Erin C
authors.initials: EC
authors.lastname: Dunn
authors.affiliation: Division of Adolescent Medicine, 6th Floor, Boston Children's Hospital, 33 Longwood Avenue, Boston, MA 02115, USA. Electronic address: tracy.k.richmond@childrens.harvard.edu.
authors.forename: Tracy K
authors.initials: TK
authors.lastname: Richmond
authors.affiliation: Clinical Research Center, Department of Medicine, Boston Children's Hospital, 21 Autumn St. ♯304, Boston, MA 02115, USA. Electronic address: carly.milliren@childrens.harvard.edu.
authors.forename: Carly E
authors.initials: CE
authors.lastname: Milliren
authors.affiliation: Department of Social and Behavioral Sciences, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA. Electronic address: svsubram@hsph.harvard.edu.
authors.forename: S V
authors.initials: SV
authors.lastname: Subramanian
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015233:Models, Statistical; D012111:Residence Characteristics; D012574:Schools; D012907:Smoking / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology
keywords: Adolescents; Cross-classified; Multilevel modeling; Neighborhoods; School environments