title: A dimensional approach to the psychosis spectrum between bipolar disorder and schizophrenia: the Schizo-Bipolar Scale.
abstract: BACKGROUND
  There is increasing evidence for phenomenological, biological and genetic overlap between schizophrenia and bipolar disorder, bringing into question the traditional dichotomy between them. Neurobiological models linked to dimensional clinical data may provide a better foundation to represent diagnostic variation in neuropsychiatric disorders.
  
  
  METHODS
  To capture the interaction between psychosis and affective symptoms dimensionally, we devised a brief descriptive scale based on the type and relative proportions of psychotic and affective symptoms over the illness course. The scale was administered to a series of 762 patients with psychotic disorders, including schizophrenia, schizoaffective and psychotic bipolar disorder assessed as part of the Bipolar-Schizophrenia Network for Intermediate Phenotypes (B-SNIP) study.
  
  
  RESULTS
  The resulting Schizo-Bipolar Scale scores across these disorders showed neither a clear dichotomy nor a simple continuous distribution. While the majority of cases had ratings close to prototypic schizophrenia or bipolar disorder, a large group (45% of cases) fell on the continuum between these two prototypes.
  
  
  CONCLUSIONS
  Our data suggest a hybrid conceptualization model with a representation of cases with prototypic schizophrenia or bipolar disorder at the extremes, but a large group of patients on the continuum between them that traditionally would be considered schizoaffective. A dimensional approach, using the Schizo-Bipolar Scale, characterized patients across a spectrum of psychopathology. This scale may provide a valuable means to examine the relationships between schizophrenia and psychotic bipolar disorder.
authors: Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA 02215, United States. keshavanms@gmail.com
authors: Matcheri S
authors: MS
authors: Keshavan
authors: David W
authors: DW
authors: Morris
authors: John A
authors: JA
authors: Sweeney
authors: Godfrey
authors: G
authors: Pearlson
authors: Gunvant
authors: G
authors: Thaker
authors: Larry J
authors: LJ
authors: Seidman
authors: Shaun M
authors: SM
authors: Eack
authors: Carol
authors: C
authors: Tamminga
mesh_terms: D000704:Analysis of Variance; D001714:Bipolar Disorder / Q000150:complications / Q000175:diagnosis*; D005260:Female; D006801:Humans; D008297:Male; D010641:Phenotype; D011569:Psychiatric Status Rating Scales; D011618:Psychotic Disorders / Q000175:diagnosis* / Q000209:etiology; D012559:Schizophrenia / Q000150:complications / Q000175:diagnosis*