title: Genetic co-morbidity between neuroticism, anxiety/depression and somatic distress in a population sample of adolescent and young adult twins.
abstract: BACKGROUND
  Genetic studies in adults indicate that genes influencing the personality trait of neuroticism account for substantial genetic variance in anxiety and depression and in somatic health. Here, we examine for the first time the factors underlying the relationship between neuroticism and anxiety/depressive and somatic symptoms during adolescence.
  
  
  METHODS
  The Somatic and Psychological Health Report (SPHERE) assessed symptoms of anxiety/depression (PSYCH-14) and somatic distress (SOMA-10) in 2459 adolescent and young adult twins [1168 complete pairs (35.4% monozygotic, 53% female)] aged 12-25 years (mean=15.5 ± 2.9). Differences between boys and girls across adolescence were explored for neuroticism, SPHERE-34, and the subscales PSYCH-14 and SOMA-10. Trivariate analyses partitioned sources of covariance in neuroticism, PSYCH-14 and SOMA-10.
  
  
  RESULTS
  Girls scored higher than boys on both neuroticism and SPHERE, with SPHERE scores for girls increasing slightly over time, whereas scores for boys decreased or were unchanged. Neuroticism and SPHERE scores were strongly influenced by genetic factors [heritability (h(2)) = 40-52%]. A common genetic source influenced neuroticism, PSYCH-14 and SOMA-10 (impacting PSYCH-14 more than SOMA-10). A further genetic source, independent of neuroticism, accounted for covariation specific to PSYCH-14 and SOMA-10. Environmental influences were largely specific to each measure.
  
  
  CONCLUSIONS
  In adolescence, genetic risk factors indexed by neuroticism contribute substantially to anxiety/depression and, to a lesser extent, perceived somatic health. Additional genetic covariation between anxiety/depressive and somatic symptoms, independent of neuroticism, had greatest influence on somatic distress, where it was equal in influence to the factor shared with neuroticism.
authors: Genetic Epidemiology, Queensland Institute of Medical Research, Brisbane, Australia.
authors: N K
authors: NK
authors: Hansell
authors: M J
authors: MJ
authors: Wright
authors: S E
authors: SE
authors: Medland
authors: T A
authors: TA
authors: Davenport
authors: N R
authors: NR
authors: Wray
authors: N G
authors: NG
authors: Martin
authors: I B
authors: IB
authors: Hickie
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D001008:Anxiety Disorders / Q000453:epidemiology / Q000235:genetics*; D002648:Child; D015897:Comorbidity; D003866:Depressive Disorder / Q000453:epidemiology / Q000235:genetics*; D004200:Diseases in Twins; D005260:Female; D020022:Genetic Predisposition to Disease; D014644:Genetic Variation; D006801:Humans; D008297:Male; D008957:Models, Genetic; D009497:Neurotic Disorders / Q000453:epidemiology / Q000235:genetics*; D010552:Personality Assessment; D057566:Self Report; D017678:Sex Distribution; D012931:Social Environment; D013001:Somatoform Disorders / Q000453:epidemiology / Q000235:genetics*; D014427:Twins / Q000235:genetics / Q000706:statistics & numerical data; D055815:Young Adult