A symptom-based continuum of psychosis explains cognitive and real-world functional deficits better than traditional diagnoses

Schizophr Res. 2019 Jun;208:344-352. doi: 10.1016/j.schres.2019.01.024. Epub 2019 Jan 31.

Abstract

Background: Patients with psychotic spectrum disorders share overlapping clinical/biological features, making it often difficult to separate them into a discrete nosology (i.e., Diagnostic and Statistical Manual of Mental Disorders [DSM]).

Methods: The current study investigated whether a continuum classification scheme based on symptom burden would improve conceptualizations for cognitive and real-world dysfunction relative to traditional DSM nosology. Two independent samples (New Mexico [NM] and Bipolar and Schizophrenia Network on Intermediate Phenotypes [B-SNIP]) of patients with schizophrenia (NM: N = 93; B-SNIP: N = 236), bipolar disorder Type I (NM: N = 42; B-SNIP: N = 195) or schizoaffective disorder (NM: N = 15; B-SNIP: N = 148) and matched healthy controls (NM: N = 64; B-SNIP: N = 717) were examined. Linear regressions examined how variance differed as a function of classification scheme (DSM diagnosis, negative and positive symptom burden, or a three-cluster solution based on symptom burden).

Results: Symptom-based classification schemes (continuous and clustered) accounted for a significantly larger portion of captured variance of real-world functioning relative to DSM diagnoses across both samples. The symptom-based classification schemes accounted for large percentages of variance for general cognitive ability and cognitive domains in the NM sample. However, in the B-SNIP sample, symptom-based classification schemes accounted for roughly equivalent variance as DSM diagnoses. A potential mediating variable across samples was the strength of the relationship between negative symptoms and impaired cognition.

Conclusions: Current results support suggestions that a continuum perspective of psychopathology may be more powerful for explaining real-world functioning than the DSM diagnostic nosology, whereas results for cognitive dysfunction were sample dependent.

Keywords: Classification; Cluster; Hierarchical Taxonomy of Psychopathology (HiTOP); Psychotic spectrum disorders; Research Domain Criteria (RDoC); Symptoms.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Adult
  • Bipolar Disorder / classification
  • Bipolar Disorder / diagnosis
  • Bipolar Disorder / psychology
  • Cognition Disorders / classification
  • Cognition Disorders / diagnosis
  • Cognition Disorders / psychology*
  • Cost of Illness
  • Diagnostic and Statistical Manual of Mental Disorders
  • Emotional Intelligence* / classification
  • Female
  • Humans
  • Male
  • Middle Aged
  • Neuropsychological Tests
  • Phenotype
  • Psychiatric Status Rating Scales
  • Psychotic Disorders / classification
  • Psychotic Disorders / diagnosis
  • Psychotic Disorders / psychology*
  • Symptom Assessment / classification
  • Symptom Assessment / psychology*
  • Young Adult