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Original Investigation
December 2018

The Latent Structure of Negative Symptoms in Schizophrenia

Author Affiliations
  • 1Department of Psychology, University of Georgia, Athens
  • 2Department of Psychology, University of Nevada, Las Vegas
  • 3Department of Psychiatry, Weill Cornell Medicine, New York, New York
  • 4Department of Psychiatry, University of California, San Diego
  • 5Psychology Service, Veterans Affairs San Diego Healthcare System, San Diego, California
  • 6Department of Psychiatry, University of Nevada, Reno
  • 7Department of Psychiatry, University of Maryland School of Medicine, Baltimore
  • 8Maryland Psychiatric Research Center, Catonsville
JAMA Psychiatry. 2018;75(12):1271-1279. doi:10.1001/jamapsychiatry.2018.2475
Key Points

Question  What is the latent structure of negative symptoms in schizophrenia?

Findings  Three cross-sectional studies were conducted on 860 outpatients with schizophrenia who underwent rating with the 3 most conceptually contemporary measures. Confirmatory factor analysis indicated that the 1- and 2-factor models provided a poor fit for the data; however, 5-factor and hierarchical models provided an excellent fit.

Meaning  These findings suggest that a change is warranted regarding diagnostic criteria for schizophrenia, how pathophysiological mechanisms are explored, and how to search for targeted treatments for negative symptoms.

Abstract

Importance  Negative symptoms are associated with a range of poor clinical outcomes, and currently available treatments generally do not produce a clinically meaningful response. Limited treatment progress may be owing in part to poor clarity regarding latent structure. Prior studies have inferred latent structure using exploratory factor analysis, which has led to the conclusion that there are 2 dimensions reflecting motivation and pleasure (MAP) and diminished expressivity (EXP) factors. However, whether these conclusions are statistically justified remains unclear because exploratory factor analysis does not test latent structure. Confirmatory factor analysis (CFA) is needed to test competing models regarding the latent structure of a construct.

Objective  To evaluate the fit of 4 models of the latent structure of negative symptoms in schizophrenia using CFA.

Design, Setting, and Participants  Three cross-sectional studies were conducted on outpatients with schizophrenia who were rated on the 3 most conceptually contemporary measures: Scale for the Assessment of Negative Symptoms (SANS), Brief Negative Symptom Scale (BNSS), and Clinical Assessment Interview for Negative Symptoms (CAINS). Confirmatory factor analysis evaluated the following 4 models: (1) a 1-factor model; (2) a 2-factor model with EXP and MAP factors; (3) a 5-factor model with separate factors for the 5 domains of the National Institute of Mental Health consensus development conference (blunted affect, alogia, anhedonia, avolition, and asociality); and (4) a hierarchical model with 2 second-order factors reflecting EXP and MAP and 5 first-order factors reflecting the 5 consensus domains.

Main Outcomes and Measures  Outcomes included CFA model fit statistics derived from symptom severity scores on the SANS, BNSS, and CAINS.

Results  The study population included 860 outpatients with schizophrenia (68.0% male; mean [SD] age, 43.0 [11.4] years). Confirmatory factor analysis was conducted on each scale, including 268 patients for the SANS, 192 for the BNSS, and 400 for the CAINS. The 1- and 2-factor models provided poor fit for the SANS, BNSS, and CAINS as indicated by comparative fit indexes (CFIs) and Tucker Lewis indexes (TLIs) less than 0.950, RMSEAs that exceeded the 0.080 threshold, and WRMRs greater than 1.00. The 5-factor and hierarchical models provided excellent fit, with the 5-factor model being more parsimonious. The CFIs and TLIs met the 0.95 threshold and the 1.00 threshold for both factor models with all 3 measures. Interestingly, the RMSEAs for the 5-factor model and the hierarchical model fell under the 0.08 threshold for the BNSS and the CAINS but not the SANS.

Conclusions and Relevance  These findings suggest that the recent trend toward conceptualizing the latent structure of negative symptoms as 2 distinct dimensions does not adequately capture the complexity of the construct. The latent structure of negative symptoms is best conceptualized in relation to the 5 consensus domains. Implications for identifying pathophysiological mechanisms and targeted treatments are discussed.

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