title: Is relatively young age within a school year a risk factor for mental health problems and poor school performance? A population-based cross-sectional study of adolescents in Oslo, Norway.
abstract: BACKGROUND
  Several studies have shown that children who are relatively young within a school year are at greater risk for poorer school performance compared with their older peers. One study also reported that relative age within a school year is an independent risk factor for emotional and behavioral problems. The objective of this study was to test the hypothesis that relatively younger adolescents in the multiethnic population of Oslo have poorer school performance and more mental health problems than their relatively older classmates within the same school year.
  
  
  METHODS
  This population-based cross-sectional study included all 10th-grade pupils enrolled in 2000 and 2001 in the city of Oslo. The participation rate was 88%. Of the 6,752 pupils in the study sample, 25% had a non-Norwegian background. Mental health problems were quantified using the abbreviated versions of Symptom Check List-25 (SCL-10) and the Strength and Difficulties Questionnaire (SDQ). Information on school performances and mental health problems were self-reported. We controlled for confounding factors including parental educational level, social support, gender, and ethnicity.
  
  
  RESULTS
  The youngest one-third of pupils had significantly lower average school grades than the middle one-third and oldest one-third of their classmates (p < 0.001). Of the mental health problems identified in the questionnaires, the groups differed only on peer problems; the youngest one-third reported significantly more problems than the middle and oldest groups (p < 0.05). Age within a school year and gender showed significant interactions with total SDQ score, SDQ peer problems score, SDQ pro social score, and SCL-10 score. After stratifying for gender, the peer problem scores differed significantly between age groups only among boys. The SCL-10 score was significant, but only in girls and in the opposite direction to that expected, with the oldest pupils having significantly higher scores than the other two groups (p < 0.05).
  
  
  CONCLUSIONS
  In adolescents from a multicultural city in Norway, relative age within a school year significantly influenced academic performance. In contrast to data from Great Britain, relative age within a school year was not an important risk factor for mental health problems in adolescents in Oslo.
authors.affiliation: Institute of General Practice and Community Medicine, University of Oslo, Blindern, Oslo 0318, Norway. lars.lien@medisin.uio.no
authors.forename: Lars
authors.initials: L
authors.lastname: Lien
authors.forename: Kristian
authors.initials: K
authors.lastname: Tambs
authors.forename: Brit
authors.initials: B
authors.lastname: Oppedal
authors.forename: Sonja
authors.initials: S
authors.lastname: Heyerdahl
authors.forename: Espen
authors.initials: E
authors.lastname: Bjertness
mesh_terms: D000293:Adolescent; D000367:Age Factors; D019958:Attention Deficit and Disruptive Behavior Disorders / Q000453:epidemiology* / Q000208:ethnology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D018864:Cultural Diversity; D004522:Educational Status; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D008913:Minority Groups / Q000523:psychology; D009664:Norway / Q000453:epidemiology; D012307:Risk Factors; D012574:Schools; D012647:Self-Assessment; D012737:Sex Factors; D012944:Social Support; D013315:Stress, Psychological / Q000453:epidemiology* / Q000208:ethnology; D013334:Students / Q000523:psychology*; D011795:Surveys and Questionnaires