title: Premorbid school performance in twins concordant and discordant for bipolar disorder.
abstract: BACKGROUND
  Although the genetic risk to develop bipolar disorder is present from conception, the first frank symptoms of the illness generally become evident in late adolescence or early adulthood. However, except for pediatric bipolar disorder (PBD), it is still unclear when the first signs of the illness in adults become apparent and whether these are related to the genetic risk to develop bipolar disorder. This study examined whether underperformance at school precedes the onset of the illness and is a genetically related risk marker for developing bipolar disorder.
  
  
  METHODS
  Information on school performance was obtained using objective archival data from 53 bipolar twin pairs (24 monozygotic (MZ), 29 dizygotic (DZ)) and 42 healthy matched control twin pairs (23 MZ, 19 DZ).
  
  
  RESULTS
  Affected twin pairs completed significantly fewer years of education than did control twin pairs with no difference between bipolar patients and their non-bipolar cotwins. The underperformance at school in the affected twin pairs occurred in early adolescence at a significantly younger age than the control twin pairs and preceded the onset of the first frank episode of bipolar disorder by thirteen years. Median age at onset of underperformance was not different in the patients and their non-bipolar cotwins. The association between liability of bipolar disease and age of first underperformance was significant and could be explained by genetic factors.
  
  
  CONCLUSIONS
  The sample is not a population based twin sample.
  
  
  CONCLUSIONS
  Underperformance at school during early adolescence may be a genetic marker for the vulnerability to develop bipolar disorder.
authors.affiliation: Reinier van Arkel groep, 's-Hertogenbosch, The Netherlands. r.vonk@RvAgroep.nl
authors.forename: R
authors.initials: R
authors.lastname: Vonk
authors.forename: A C
authors.initials: AC
authors.lastname: van der Schot
authors.forename: G C M
authors.initials: GC
authors.lastname: van Baal
authors.forename: C J
authors.initials: CJ
authors.lastname: van Oel
authors.forename: W A
authors.initials: WA
authors.lastname: Nolen
authors.forename: R S
authors.initials: RS
authors.lastname: Kahn
mesh_terms: D000328:Adult; D001714:Bipolar Disorder / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics*; D004522:Educational Status; D005260:Female; D005819:Genetic Markers; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics
chemical_list: D005819:Genetic Markers