title: Disentangling the causal inter-relationship between negative life events and depressive symptoms in women: a longitudinal twin study.
abstract: BACKGROUND
  Negative life events are strongly associated with the development of depression. However, the etiologic relationship between life events and depression is complex. Evidence suggests that life events can cause depression, and depression increases the risk for life events. Additionally, third factors influencing both phenotypes may be involved. In this work we sought to disentangle these relationships using a genetically informative longitudinal design.
  
  
  METHODS
  Adult female twins (n=536, including 281 twin pairs) were followed up for measurements of negative life event exposure and depressive symptoms. Four follow-ups were completed, each approximately 3 months apart. Model fitting was carried out using the Mx program.
  
  
  RESULTS
  The best-fitting model included causal paths from life events to depressive symptoms for genetic and shared environmental risk factors, whereas paths from depressive symptoms to life events were apparent for shared environmental factors. Shared latent influence on both phenotypes was found for individual-specific effects.
  
  
  CONCLUSIONS
  Life events and depressive symptoms have complex inter-relationships that differ across sources of variance. The results of the model, if replicated, indicate that reducing life event exposure would reduce depressive symptoms and that lowering depressive symptoms would decrease the occurrence of negative life events.
authors.affiliation: Department of Psychiatry and Neuropsychology, South Limburg Mental Health Research and Teaching Network, EURON, Maastricht University, Maastricht, The Netherlands. m.wichers@sp.unimaas.nl
authors.forename: M
authors.initials: M
authors.lastname: Wichers
authors.forename: H H
authors.initials: HH
authors.lastname: Maes
authors.forename: N
authors.initials: N
authors.lastname: Jacobs
authors.forename: C
authors.initials: C
authors.lastname: Derom
authors.forename: E
authors.initials: E
authors.lastname: Thiery
authors.forename: K S
authors.initials: KS
authors.lastname: Kendler
mesh_terms: D000328:Adult; D003863:Depression / Q000209:etiology* / Q000235:genetics; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D006801:Humans; D008016:Life Change Events; D008137:Longitudinal Studies; D015233:Models, Statistical; D012307:Risk Factors; D014429:Twins, Dizygotic / Q000235:genetics / Q000523:psychology; D014430:Twins, Monozygotic / Q000235:genetics / Q000523:psychology