title: Development and validation of an international risk prediction algorithm for episodes of major depression in general practice attendees: the PredictD study.
abstract: BACKGROUND
  Strategies for prevention of depression are hindered by lack of evidence about the combined predictive effect of known risk factors.
  
  
  OBJECTIVE
  To develop a risk algorithm for onset of major depression.
  
  
  METHODS
  Cohort of adult general practice attendees followed up at 6 and 12 months. We measured 39 known risk factors to construct a risk model for onset of major depression using stepwise logistic regression. We corrected the model for overfitting and tested it in an external population.
  
  
  METHODS
  General practices in 6 European countries and in Chile.
  
  
  METHODS
  In Europe and Chile, 10 045 attendees were recruited April 2003 to February 2005. The algorithm was developed in 5216 European attendees who were not depressed at recruitment and had follow-up data on depression status. It was tested in 1732 patients in Chile who were not depressed at recruitment. Main Outcome Measure DSM-IV major depression.
  
  
  RESULTS
  Sixty-six percent of people approached participated, of whom 89.5% participated again at 6 months and 85.9%, at 12 months. Nine of the 10 factors in the risk algorithm were age, sex, educational level achieved, results of lifetime screen for depression, family history of psychological difficulties, physical health and mental health subscale scores on the Short Form 12, unsupported difficulties in paid or unpaid work, and experiences of discrimination. Country was the tenth factor. The algorithm's average C index across countries was 0.790 (95% confidence interval [CI], 0.767-0.813). Effect size for difference in predicted log odds of depression between European attendees who became depressed and those who did not was 1.28 (95% CI, 1.17-1.40). Application of the algorithm in Chilean attendees resulted in a C index of 0.710 (95% CI, 0.670-0.749).
  
  
  CONCLUSIONS
  This first risk algorithm for onset of major depression functions as well as similar risk algorithms for cardiovascular events and may be useful in prevention of depression.
authors.affiliation: Department of Mental Health Sciences, University College London Medical School, Royal Free Campus, Rowland Hill Street, London NW3 2PF, England. m.king@medsch.ucl.ac.uk
authors.forename: Michael
authors.initials: M
authors.lastname: King
authors.forename: Carl
authors.initials: C
authors.lastname: Walker
authors.forename: Gus
authors.initials: G
authors.lastname: Levy
authors.forename: Christian
authors.initials: C
authors.lastname: Bottomley
authors.forename: Patrick
authors.initials: P
authors.lastname: Royston
authors.forename: Scott
authors.initials: S
authors.lastname: Weich
authors.forename: Juan Angel
authors.initials: JA
authors.lastname: Bellón-Saameño
authors.forename: Berta
authors.initials: B
authors.lastname: Moreno
authors.forename: Igor
authors.initials: I
authors.lastname: Svab
authors.forename: Danica
authors.initials: D
authors.lastname: Rotar
authors.forename: J
authors.initials: J
authors.lastname: Rifel
authors.forename: Heidi-Ingrid
authors.initials: HI
authors.lastname: Maaroos
authors.forename: Anu
authors.initials: A
authors.lastname: Aluoja
authors.forename: Ruth
authors.initials: R
authors.lastname: Kalda
authors.forename: Jan
authors.initials: J
authors.lastname: Neeleman
authors.forename: Mirjam I
authors.initials: MI
authors.lastname: Geerlings
authors.forename: Miguel
authors.initials: M
authors.lastname: Xavier
authors.forename: Idalmiro
authors.initials: I
authors.lastname: Carraça
authors.forename: Manuel
authors.initials: M
authors.lastname: Gonçalves-Pereira
authors.forename: Benjamin
authors.initials: B
authors.lastname: Vicente
authors.forename: Sandra
authors.initials: S
authors.lastname: Saldivia
authors.forename: Roberto
authors.initials: R
authors.lastname: Melipillan
authors.forename: Francisco
authors.initials: F
authors.lastname: Torres-Gonzalez
authors.forename: Irwin
authors.initials: I
authors.lastname: Nazareth
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000465:Algorithms; D003865:Major Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology*; D005194:Family Practice / Q000592:standards* / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D018570:Risk Assessment