title: Educational achievement and vocational career in twins - a Swedish national cohort study.
abstract: OBJECTIVE
  To investigate how being born and raised as a twin is associated with IQ, educational achievement and vocational career.
  
  
  METHODS
  Register study in a national birth cohort, complemented with a siblings study. The study population included 13,368 individuals born and raised as twins and 837,752 singletons, including 3019 siblings of twins, in the Swedish birth cohorts of 1973-1981. Our outcome measures were mean grade points on a five point scale from ninth grade of primary school at 15-16 years, IQ tests on a nine grade point scale from male conscripts at 18-19 years, highest completed education, disability benefits, work income and employment at 27-35 years of age.
  
  
  RESULTS
  Twins had slightly better mean grade point averages in ninth grade; +0.08 (95% CI 0.04-0.11) and more often had completed a university education in young adulthood; OR 1.16 (1.02-1.21) compared with singleton siblings, despite male twins having a slightly lower IQ at military conscription compared with male singletons. Employment rates, mean income and disability benefits were similar in twins and singletons.
  
  
  CONCLUSIONS
  Twins have slightly better educational careers and similar vocational careers compared with those born as singletons.
authors.affiliation: Centre for Health Equity Studies, Karolinska Institutet/Stockholm University, Sweden. anders.hjern@chess.su.se
authors.forename: Anders
authors.initials: A
authors.lastname: Hjern
authors.forename: Cecilia
authors.initials: C
authors.lastname: Ekeus
authors.forename: Finn
authors.initials: F
authors.lastname: Rasmussen
authors.forename: Frank
authors.initials: F
authors.lastname: Lindblad
mesh_terms: D000293:Adolescent; D000328:Adult; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D006801:Humans; D008297:Male; D009790:Occupations; D013548:Sweden; D055815:Young Adult