title: Major depression and life satisfaction: a population-based twin study.
abstract: BACKGROUND
  The extent to which positive and negative indicators of mental health share etiological influences has been studied to a limited degree only. This study examines the genetic and environmental influences on association between liability to lifetime DSM-IV Major Depressive Disorder (MDD) and dispositional life satisfaction (LS).
  
  
  METHODS
  Two-wave questionnaire data on LS (assessed 6 years apart) and lifetime MDD obtained by structured clinical interviews in a population-based sample of adult twins were analysed using structural equation modelling in Mx.
  
  
  RESULTS
  The prevalence of lifetime MDD was estimated to be 11.1% and 15.8% in males and females, respectively. Individuals fulfilling the criteria for MDD reported significantly lower levels of LS. The co-variation in MDD and dispositional LS was found to be accounted for by genetic and unique environmental influences only. The phenotypic correlation was estimated to be 0.36, of which genetic influences accounted for 74% and environmental factors the remaining 26%. The correlation between genetic factors for MDD and LS was estimated to be -0.55 and the correlation between unique environmental factors to be -0.22. Heritability was estimated to 0.34 and 0.72 for MDD and LS, respectively.
  
  
  CONCLUSIONS
  The sample consists of twins only and there are limitations associated with the twin design.
  
  
  CONCLUSIONS
  Whereas genetic influences on vulnerability to lifetime MDD are considerably shared with liability to (low) LS, environmental influences are more distinct. Thus, environmental factors associated with risk of MDD do not strongly impact on dispositional LS, and conversely, environmental factors influencing dispositional LS do not strongly buffer against MDD.
authors.affiliation: Division of Mental Health, The Norwegian Institute of Public Health, Oslo, Norway. Ragnhild.bang.nes@fhi.no
authors.forename: Ragnhild B
authors.initials: RB
authors.lastname: Nes
authors.forename: Nikolai O
authors.initials: NO
authors.lastname: Czajkowski
authors.forename: Espen
authors.initials: E
authors.lastname: Røysamb
authors.forename: Ragnhild E
authors.initials: RE
authors.lastname: Orstavik
authors.forename: Kristian
authors.initials: K
authors.lastname: Tambs
authors.forename: Ted
authors.initials: T
authors.lastname: Reichborn-Kjennerud
mesh_terms: D000293:Adolescent; D000328:Adult; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D004200:Diseases in Twins / Q000175:diagnosis / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007406:Interview, Psychological; D008297:Male; D009664:Norway / Q000453:epidemiology; D010549:Personal Satisfaction; D015995:Prevalence; D012307:Risk Factors; D011795:Surveys and Questionnaires; D055815:Young Adult