title: Searching for valid psychiatric phenotypes: discrete latent variable models.
abstract: BACKGROUND
  A primary challenge in psychiatric genetics is the lack of a completely validated system of classification for mental disorders. Appropriate statistical methods are needed to empirically derive more homogenous disorder subtypes.
  
  
  METHODS
  Using the framework of Robins and Guze's ('Establishment of diagnostic validity in psychiatric illness: its application to schizophrenia', American Journal of Psychiatry, 1970, 126(7), 983-987) five phases, latent variable models to derive and validate diagnostic groups are described. A process of iterative validation is proposed through which refined phenotypes would facilitate research on genetics, pathogenesis, and treatment, which would in turn aid further refinement of disorder definitions.
  
  
  CONCLUSIONS
  Latent variable methods are useful tools for defining and validating psychiatric phenotypes. Further methodological research should address sample size issues and application to iterative validation.
authors.affiliation: Department of Psychiatry and Behavioral Sciences, Johns Hopkins University School of Medicine, Baltimore, MD, USA. jeannie-marie@jhu.edu
authors.forename: Jeannie-Marie S
authors.initials: JM
authors.lastname: Leoutsakos
authors.forename: Peter P
authors.initials: PP
authors.lastname: Zandi
authors.forename: Karen
authors.initials: K
authors.lastname: Bandeen-Roche
authors.forename: Constantine G
authors.initials: CG
authors.lastname: Lyketsos
mesh_terms: D039721:Diagnostic and Statistical Manual of Mental Disorders; D005500:Follow-Up Studies; D006801:Humans; D001523:Mental Disorders / Q000145:classification* / Q000175:diagnosis*; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D054928:Validation Studies as Topic