title: Genetic and environmental influences on psychological distress in the population: General Health Questionnaire analyses in UK twins.
abstract: BACKGROUND
  The General Health Questionnaire (GHQ) is the most popular screening instrument for detecting psychiatric disorders in community samples. Using longitudinal data of a large sample of UK twin pairs, we explored (i) heritabilities of the four scales and the total score; (ii) the genetic stability over time; and (iii) the existence of differential heritable influences at the high (ill) and low (healthy) tail of the distribution.
  
  
  METHODS
  At baseline we assessed the GHQ in 627 MZ and 1323 DZ female pairs and at a second occasion (3.5 years later) for a small subsample (90 MZ and 270 DZ pairs). Liability threshold models and raw ordinal maximum likelihood were used to estimate twin correlations and to fit longitudinal genetic models. We estimated extreme group heritabilities of the GHQ distribution by using a model-fitting implementation of the DeFries-Fulker regression method for selected twin data.
  
  
  RESULTS
  Heritabilities for Somatic Symptoms, Anxiety, Social Dysfunction, Depression and total score were 0.37, 0.40, 0.20, 0.42 and 0.44, respectively. The contribution of shared genetic factors to the correlations between time points is substantial for the total score (73%). Group heritabilities of 0.48 and 0.43 were estimated for the top and bottom 10% of the total GHQ score distribution, respectively.
  
  
  CONCLUSIONS
  The overall heritability of the GHQ as a measure of psychosocial distress was substantial (44%), with all scales having significant additive genetic influences that persisted across time periods. Extreme group analyses suggest that the genetic control of resilience is as important as the genetic control of vulnerability.
authors.affiliation: Social, Genetic and Developmental Psychiatry Centre, Institute of Psychiatry and Twin Research and Genetic Epidemiology Unit. St Thomas' Hospital, London.
authors.forename: F V
authors.initials: FV
authors.lastname: Rijsdijk
authors.forename: H
authors.initials: H
authors.lastname: Snieder
authors.forename: J
authors.initials: J
authors.lastname: Ormel
authors.forename: P
authors.initials: P
authors.lastname: Sham
authors.forename: D P
authors.initials: DP
authors.lastname: Goldberg
authors.forename: T D
authors.initials: TD
authors.lastname: Spector
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015331:Cohort Studies; D004200:Diseases in Twins; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D001523:Mental Disorders / Q000453:epidemiology* / Q000235:genetics*; D008875:Middle Aged; D008957:Models, Genetic; D012307:Risk Factors; D013315:Stress, Psychological / Q000453:epidemiology* / Q000235:genetics*; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D006113:United Kingdom / Q000453:epidemiology