title: Longitudinal study of interpersonal dependency in female twins.
abstract: BACKGROUND
  Interpersonal dependence is thought to be important in a number of physical and psychological disorders. There are several developmental theories that suggest environmental influences in childhood are important.
  
  
  METHODS
  A twin study methodology was used to look at the genetic and environmental influences on interpersonal dependence as measured by a sub-scale of the Interpersonal Dependency Inventory with a population-based sample of 2230 twins.
  
  
  RESULTS
  Psychometric analysis revealed that this was a stable measure and that there was a substantial degree of construct validity. Both univariate and longitudinal twin analysis suggested that there was a modest genetic influence and a large, specific environment influence on interpersonal dependency as measured by this scale. The longitudinal analysis revealed that the genetic influence was stable over the time-scale sampled and the environmental influence was moderately stable.
  
  
  CONCLUSIONS
  This finding is at odds with theories that suggest shared environment is important in the aetiology of interpersonal dependency.
authors.affiliation: Mater Hospital Trust, Alexandra Gardens Day Hospital, Belfast, Northern Ireland.
authors.forename: F A
authors.initials: FA
authors.lastname: O'Neill
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
mesh_terms: D000704:Analysis of Variance; D003859:Dependent Personality Disorder / Q000209:etiology*; D004777:Environment; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic