Categorical vs dimensional classifications of psychotic disorders

Abstract

Objective Both categorical and dimensional methods appear relevant to classifying psychotic disorders; however, there is no clear consensus on the most appropriate categories and dimensions or on the best approach for constructing nosologic criteria that integrate these 2 methods. This review examines the evidence on specific dimensions and categories that would best characterize psychoses. Method Entries in the MEDLINE database between 1980 and 2011 were searched for studies of the dimensional and/or categorical structure of psychosis. Studies were included if samples represented a spectrum of psychotic disorders and dimensions/categories were empirically derived using principal components analysis, factor analysis, or latent class analysis. Results Most dimensional studies observed 4 or 5 dimensions within psychosis, with positive, negative, disorganization, and affective symptom domains most frequently reported. Substance abuse, anxiety, early onset/developmental, insight, cognition, hostility, and behavioral/social disturbance dimensions appeared in some studies. Categorical studies suggested 3 to 7 major classes within psychosis, including a class similar to Kraepelin’s dementia praecox and one or more classes with significant mood components. Only 2 studies compared the relative fit of empirically derived dimensions and categories within the same data set, and each had significant limitations. Conclusion There is relatively consistent evidence on appropriate categories and dimensions for characterizing psychoses. However, the lack of studies directly comparing or combining these approaches provides insufficient evidence for definitive conclusions about their relative merits and integration. The authors provide specific recommendations for designing future studies to identify valid dimensions and/or categories of the psychoses and investigate hybrid approaches to model the structure of the underlying illnesses.

Abnormal perfusion fluctuation and perfusion connectivity in bipolar disorder measured by dynamic arterial spin labeling

“…Instead of separate dimensions for negative and disorganization symptoms, we observed a combined dimension of these two symptoms. This may be explained by limitations of the adopted rating scales that did not distinguish primary and secondary negative symptoms . The significantly lower psychosis ratio, PANSS‐positive scales, positive dimensional scores, and, negative and disorganized dimensional scores were observed in the investigated BD patients compared to the BSNIP subjects.…”

Stability of ICD-10 diagnoses in patients with psychotic symptoms

“…S druge strane dimenzionalni pristup psihijatrijsku problematiku posmatra kao stanja koja "se stapaju" jedna u drugo gotovo neprimetno i da jasna granica među njima ne postoji. Iako naš rad ne govori direktno o dimenzionalnim kategorijama, mnogi od problema koje postoje u kliničkoj praksi sa kategorijalnim dijagnozama bi, barem teorijski, bili rešeni dimenzionalnim pristupom (mada bi se sigurno otvorili drugi problem) [13]. Treći, etiološki, pristup dijagnostici je nešto što se zagovornici i kategorijalnog i dimenzionalnog modela slažu da bi bio najbolji model, ali trenutno naša naučna saznanja nisu na nivou koji bi omogućio uspostavljanje ovakve dijagnostičke nozologije.…”

Searching human brain for mechanisms of psychiatric disorders. Implications for studies on schizophrenia

“…Within the realm of psychiatric disorders, several clinical domains and/or categorical diagnosis often coexist, such as psychosis, anxiety and depression (Braga et al, 2013; Cerda et al, 2010; Dernovsek and Sprah, 2009; Pallanti et al, 2013; Potuzak et al, 2012; Simon, 2009). The variety of psychiatric disorders represented in the large Scottish family carrying a translocation of the Disrupted In Schizophrenia (DISC-1) gene, and substantial overlap of genetic vulnerabilities among several psychiatric disorders further weaken clinical boundaries between psychiatric conditions (Blackwood et al, 2001; Millar et al, 2001; Millar et al, 2000; Smoller, 2013).…”