title: Age at fatherhood: heritability and associations with psychiatric disorders.
abstract: Advancing paternal age has been linked to psychiatric disorders. These associations might be caused by the increased number of de novo mutations transmitted to offspring of older men. It has also been suggested that the associations are confounded by a genetic liability for psychiatric disorders in parents. The aim of this study was to indirectly test the confounding hypotheses by examining if there is a genetic component to advancing paternal age and if men with a genetic liability for psychiatric disorders have children at older ages.
  
  
  
  We examined the genetic component to advancing paternal age by utilizing the twin model in a cohort of male twins (N = 14 679). We also studied ages at childbirth in men with or without schizophrenia, bipolar disorder and/or autism spectrum disorder. Ages were examined in: (1) healthy men, (2) affected men, (3) healthy men with an affected sibling, (4) men with healthy spouses, (5) men with affected spouses, and (6) men with healthy spouses with an affected sibling.
  
  
  
  The twin analyses showed that late fatherhood is under genetic influence (heritability = 0.33). However, affected men or men with affected spouses did not have children at older ages. The same was found for healthy individuals with affected siblings. Instead, these men were generally having children at younger ages.
  
  
  
  Although there is a genetic component influencing late fatherhood, our data suggest that the associations are not explained by psychiatric disorders or a genetic liability for psychiatric disorders in the parent.
authors: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Sweden.
authors: E M
authors: EM
authors: Frans
authors: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Sweden.
authors: P
authors: P
authors: Lichtenstein
authors: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Sweden.
authors: C M
authors: CM
authors: Hultman
authors: Department of Medical Epidemiology and Biostatistics,Karolinska Institutet,Sweden.
authors: R
authors: R
authors: Kuja-Halkola
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000067877:Autism Spectrum Disorder / Q000453:epidemiology* / Q000235:genetics; D001714:Bipolar Disorder / Q000453:epidemiology* / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D010331:Paternal Age; D012042:Registries; D012559:Schizophrenia / Q000453:epidemiology* / Q000235:genetics; D013548:Sweden / Q000453:epidemiology
keywords: 
                 de novo mutations; Autism; bipolar disorder; familial confounding; heritability; paternal age; schizophrenia; sibling comparison; twin model