title: The genetic aetiology of childhood depression: a review.
abstract: BACKGROUND
  We review the evidence for the familiality of major depressive disorder (MDD) and the genetic aetiology of depressive symptoms in children and adolescents.
  
  
  METHODS
  Databases and reference lists were searched for family, twin and adoption studies of childhood MDD and childhood depressive symptoms. Data from independent family studies that fulfilled specified inclusion criteria were pooled and odds ratios were calculated for top-down and bottom-up family studies.
  
  
  RESULTS
  Estimates of familial risk differ by control group and by study design (odds ratio range 1.70, 3.98). Twin studies show that depressive symptoms in young people are heritable although rater and measurement issues are important. Adoption studies show little evidence for a genetic influence on depressive symptoms.
  
  
  CONCLUSIONS
  MDD in young people is familial although control group and study design affect the magnitude of the familial risk. Estimates of heritability from twin and adoption studies vary widely and few firm conclusions can be made regarding the genetic aetiology of depressive symptoms in childhood. Areas that require future work include the examination of rater effects, measurement issues, the effects of age and comorbidity and reasons for the discrepancy between twin and adoption findings.
authors.affiliation: University of Wales College of Medicine, Heath Park, Cardiff, UK.
authors.forename: Frances
authors.initials: F
authors.lastname: Rice
authors.forename: Gordon
authors.initials: G
authors.lastname: Harold
authors.forename: Anita
authors.initials: A
authors.lastname: Thapar
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002648:Child; D003866:Depressive Disorder / Q000235:genetics*; D005190:Family / Q000523:psychology; D006801:Humans; D014427:Twins / Q000523:psychology