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Schizophr Res. 2019 Jan 30. pii: S0920-9964(19)30027-1. doi: 10.1016/j.schres.2019.01.024. [Epub ahead of print]

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

Author information

1
The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA. Electronic address: fhanlon@mrn.org.
2
Department of Psychology, University of New Mexico, 2001 Redondo S Dr., Albuquerque, NM 87106, USA. Electronic address: ryeo@unm.edu.
3
The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA. Electronic address: nshaff@mrn.org.
4
The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA. Electronic address: cwertz@mrn.org.
5
The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA. Electronic address: adodd@mrn.org.
6
Department of Psychiatry, University of New Mexico School of Medicine, MSC09 5030, 1 University of New Mexico, Albuquerque, NM 87131, USA. Electronic address: JBustillo@salud.unm.edu.
7
Psychiatry and Behavioral Health Clinical Program, Presbyterian Healthcare System, 1325 Wyoming Blvd. NE, Albuquerque, NM 87112, USA. Electronic address: sstromber@phs.org.
8
Department of Psychiatry, University of New Mexico School of Medicine, MSC09 5030, 1 University of New Mexico, Albuquerque, NM 87131, USA. Electronic address: delin@salud.unm.edu.
9
Department of Psychiatry, University of New Mexico School of Medicine, MSC09 5030, 1 University of New Mexico, Albuquerque, NM 87131, USA. Electronic address: SAbrams@salud.unm.edu.
10
The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA. Electronic address: jliu@mrn.org.
11
The Mind Research Network/Lovelace Biomedical and Environmental Research Institute, 1101 Yale Blvd. NE, Albuquerque, NM 87106, USA; Department of Psychology, University of New Mexico, 2001 Redondo S Dr., Albuquerque, NM 87106, USA; Department of Psychiatry, University of New Mexico School of Medicine, MSC09 5030, 1 University of New Mexico, Albuquerque, NM 87131, USA; Department of Neurology, University of New Mexico School of Medicine, MSC10 5620, 1 University of New Mexico, Albuquerque, NM 87131, USA. Electronic address: amayer@mrn.org.

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

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