title: Partitioning the etiology of hoarding and obsessive-compulsive symptoms.
abstract: BACKGROUND
  Until recently, hoarding was considered an obsessive-compulsive symptom (OCS). However, current evidence suggests that these two phenotypes may be clinically, and perhaps etiologically, distinct. Both hoarding and OCS have a genetic etiology, but the degree of unique and shared genetic contributions to these phenotypes has not been well studied.
  
  
  METHODS
  Prevalence rates were assessed for hoarding and OCS in a sample of adult twin pairs (n = 7906 twins) and their family members from The Netherlands Twin Register (total sample = 15,914). Using Mplus, genetic analyses using liability threshold models were conducted for both phenotypes, for their co-morbidity, and for specific hoarding symptoms (cluttering, discarding and acquiring).
  
  
  RESULTS
  Of the total sample, 6.7% met criteria for clinically significant hoarding; endorsement of all three hoarding symptoms was > or = 79%. Men had slightly higher rates than women. Also, 5.7% met criteria for clinically significant OCS; rates were similar in males and females. Genetic factors accounted for 36% of the variance for hoarding and 40% of the variance for OCS. The genetic correlation between hoarding and OCS was 0.10. There was no evidence of sex-specific genetic contributions for hoarding or OCS. There was evidence for a genetic contribution to all hoarding symptom subtypes. Only cluttering showed evidence of a contribution from the shared environment.
  
  
  CONCLUSIONS
  OCS and hoarding are common in this population-based sample, have prevalence rates similar to those previously reported, and show significant heritability. Genetic factors contributed to the co-morbidity of both traits, although the genetic correlation between them was low.
authors: Department of Psychiatry,University of California San Francisco,San Francisco, CA,USA.
authors: C A
authors: CA
authors: Mathews
authors: Department of Psychiatry,University of California San Francisco,San Francisco, CA,USA.
authors: K
authors: K
authors: Delucchi
authors: Department of Clinical and Health Psychology,Utrecht University and Altrecht Academic Anxiety Disorders Center,Utrecht,the Netherlands.
authors: D C
authors: DC
authors: Cath
authors: Department of Biological Psychology,VU University,Amsterdam, Amsterdam,the Netherlands.
authors: G
authors: G
authors: Willemsen
authors: Department of Biological Psychology,VU University,Amsterdam, Amsterdam,the Netherlands.
authors: D I
authors: DI
authors: Boomsma
mesh_terms: D000328:Adult; D005260:Female; D000067836:Hoarding Disorder / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D006801:Humans; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D009771:Obsessive-Compulsive Disorder / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D012042:Registries