title: Socioeconomic status and sick leave granted for mental and somatic disorders: a prospective study of young adult twins.
abstract: BACKGROUND
  Low socioeconomic status (SES), indicated by low income and education, has consistently been found to be a strong predictor of sick leave. Several possible pathways from SES to sick leave have been described in previous literature, but there are also evidence indicating that the association can be confounded by common underlying factors. This study utilizes a population-based sample of employed young adult twins to estimate (i) the degree to which education and income are prospectively related to sick leave granted for mental, somatic, and any disorder, and (ii) whether these associations are confounded by familial factors.
  
  
  METHODS
  Registry data on educational attainment and income at age 30 and subsequent sick leave were available for 6,103 employed young adult twins, among which there were 2,024 complete twin pairs. The average follow-up time was 6.57 years. Individual-level associations and fixed effects within twin pairs were estimated.
  
  
  RESULTS
  Low education and income were associated with sick leave granted for both mental and somatic disorders, and with sick leave granted for any disorder. Associations were attenuated within dizygotic twin pairs and reduced to non-significance within monozygotic twin pairs, suggesting influence of familial factors on the associations between SES and sick leave.
  
  
  CONCLUSIONS
  Low SES is associated with a higher level of sick leave granted for both mental and somatic disorders among young adults, but these associations are confounded by factors that are common to co-twins. Education and income are therefore not likely to strongly affect sick leave in young adulthood.
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. fartein.ask.torvik@fhi.no.
authors.forename: Fartein Ask
authors.initials: FA
authors.lastname: Torvik
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. eivind.ystrom@fhi.no.
authors.forename: Eivind
authors.initials: E
authors.lastname: Ystrom
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. n.o.czajkowski@psyklologi.uio.no.|Department of Psychology, University of Oslo, Postbox 1049 Blindern, Oslo, 0317, Norway. n.o.czajkowski@psyklologi.uio.no.
authors.forename: Nikolai
authors.initials: N
authors.lastname: Czajkowski
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. kristian.tambs@fhi.no.
authors.forename: Kristian
authors.initials: K
authors.lastname: Tambs
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. espen.roysamb@psykologi.uio.no.|Department of Psychology, University of Oslo, Postbox 1049 Blindern, Oslo, 0317, Norway. espen.roysamb@psykologi.uio.no.
authors.forename: Espen
authors.initials: E
authors.lastname: Røysamb
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. ragnhildelise.orstavik@fhi.no.
authors.forename: Ragnhild
authors.initials: R
authors.lastname: Ørstavik
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. gunpeggy.knudsen@fhi.no.
authors.forename: Gun Peggy
authors.initials: GP
authors.lastname: Knudsen
authors.affiliation: Department of Psychiatry, Virginia Commonwealth University, 1200 East Broad Street, P. O. Box 980710, Richmond, VA, 23298-0710, USA. kendler@vcu.edu.|Virginia Institute for Psychiatric and Behavioral Genetics, Virginia Commonwealth University, Richmond, VA, 23298-0126, USA. kendler@vcu.edu.
authors.forename: Kenneth S
authors.initials: KS
authors.lastname: Kendler
authors.affiliation: Division of Mental Health, Norwegian Institute of Public Health, Postbox 4404, Oslo, Nydalen, 0403, Norway. ted.reichborn-kjennerud@fhi.no.|Institute of Clinical Medicine, University of Oslo, Postbox 1171 Blindern, Oslo, 0316, Norway. ted.reichborn-kjennerud@fhi.no.
authors.forename: Ted
authors.initials: T
authors.lastname: Reichborn-Kjennerud
mesh_terms: D000328:Adult; D005260:Female; D006801:Humans; D008297:Male; D001523:Mental Disorders; D009664:Norway; D011446:Prospective Studies; D011602:Psychophysiologic Disorders; D018582:Sick Leave / Q000706:statistics & numerical data*; D012923:Social Class; D013997:Time Factors; D014429:Twins, Dizygotic / Q000523:psychology*; D014430:Twins, Monozygotic / Q000523:psychology*