Abstract
To examine whether negative symptoms, psychosis, hostility, excitation, and mannerism (PHEM symptoms), formal thought disorders (FTD) and psychomotor retardation (PMR) are interrelated phenomena in major neurocognitive psychosis (MNP) or deficit schizophrenia and whether those domains belong to an underlying latent vector reflecting general psychopathology. In this study, we recruited 120 patients with MNP or deficit schizophrenia and 54 healthy subjects and measured the above-mentioned symptom domains. In MNP, there were significant associations between negative and PHEM symptoms, FTD and PMR. A single latent trait, which is essentially unidimensional, underlies these key domains of schizophrenia and MNP and additionally shows excellent internal consistency reliability, convergent validity, and predictive relevance. Confirmatory Tedrad Analysis indicates that this latent vector fits a reflective model. The lack of discriminant validity shows that positive (and PHEM or psychotic) and negative symptoms greatly overlap and probably measure the same latent construct. Soft independent modeling of class analogy (SIMCA) shows that MNP (diagnosis based on negative symptoms) is better modeled using PHEM symptoms, FTD, and PMR than negative symptoms. In stable phase MNP, which is a restricted sample of the schizophrenia population, negative and PHEM symptoms, FTD and PMR belong to one underlying latent vector reflecting overall severity of schizophrenia (OSOS). The bi-dimensional concept of "positive" and "negative" symptoms cannot be validated and, therefore, future research in stable phase schizophrenia should consider that the latent phenomenon OSOS as well as its reflective manifestations are the key factors of schizophrenia phenomenology.
Highlights
Schizophrenia is characterized by various symptom domains the two most important being positive symptoms, including delusions, hallucinations, excitation, hostility, disorganized thinking, and negative symptoms, including affective flattening, avolition, alogia, anhedonia (Mellor, 1991; Marneros et al, 1991; Cuesta and Peralta, 1995)
Based on these results we examined the association between negative symptoms and PHEM symptoms, formal thought disorders (FTD) and psychomotor retardation (PMR) while allowing for the intervening effects of extraneous variables
The first major finding of this study is that a single latent trait, which is essentially unidimensional, underlies the key symptom domains of schizophrenia, namely Scale for the Assessments of Negative Symptoms (SANS) and Positive and Negative Syndrome Scale (PANSS) negative, PHEM symptoms, FTD and PMR
Summary
Schizophrenia is characterized by various symptom domains the two most important being positive symptoms, including delusions, hallucinations, excitation, hostility, disorganized thinking, and negative symptoms, including affective flattening, avolition, alogia, anhedonia (Mellor, 1991; Marneros et al, 1991; Cuesta and Peralta, 1995). On the other hand, are conceptualized as emotions (hedonia), thought processes (logic thinking) and behaviors (social interactions) that the patient has lost as a consequence of the disorder (Burton, 2012). Based on this distinction between positive and negative symptoms of schizophrenia patients were subdivided according to a two-syndrome concept into those with mainly positive symptoms, named type I schizophrenia, and those with mainly negative symptoms, named type II schizophrenia (Crow, 1985). It is debated whether negative symptoms increase in severity along a continuum from the healthy state to schizophrenia patients with a “fully developed doi:10.20944/preprints201907.0147.v1 syndrome” (dimensional theory) or whether type II or deficit schizophrenia is a separate nosological class (categorical theory) (Takahashi, 2013; Kanchanatwan et al, 2018a)
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