Abstract
Problems in psychiatric classification have impeded research into psychopathology for more than a century. Here, I briefly review several new approaches to solving this problem, including the internalizing-externalizing-psychosis spectra, the 5-factor model of psychotic symptoms, and the more recent network approach. Researchers and clinicians should probably adopt an attitude of promiscuous realism and assume that a single classification system is unlikely to be effective for all purposes, and that different systems will need to be chosen for research into etiology, public mental health research, and clinical activities. Progress in understanding the risk factors and mechanisms that lead to psychopathology is most likely to be achieved by focusing on specific types of experience or symptoms such as hallucinations.
Highlights
Toward the end of the first century of schizophrenia research, a few observers noted that broad diagnoses such as schizophrenia were scarcely adequate as independent variables in research because they were defined inconsistently, failed to cleave nature at its joints, and grouped together problems which probably had little in common.[1,2]
The need for a nondiagnosis-based research strategy has become much more widely accepted in the intervening years, most notably among biological researchers such as geneticists,[3] and pharmacologists,[4] leading NIMH to recently propose the Research Domain Criteria (RDoC) approach.[5]
To add further levels of complexity, some studies have suggested that, superordinate to both the internalizingexternalizing-psychosis spectra[14] and the 5-factor model of psychosis,[15] there is a general psychopathology or “P” factor common to all psychiatric disorders, perhaps reflecting neuroticism or emotional instability
Summary
Toward the end of the first century of schizophrenia research, a few observers noted that broad diagnoses such as schizophrenia were scarcely adequate as independent variables in research because they were defined inconsistently, failed to cleave nature at its joints, and grouped together problems which probably had little in common.[1,2] At the time this was a minority position. Liddle[11] first reported 3 clusters of positive, negative, and cognitive disorganization symptoms, but more recent research has converged on 5 factors by adding depression and mania as separate factors.[12,13] To add further levels of complexity, some studies have suggested that, superordinate to both the internalizingexternalizing-psychosis spectra[14] and the 5-factor model of psychosis,[15] there is a general psychopathology or “P” factor common to all psychiatric disorders, perhaps reflecting neuroticism or emotional instability (this latter type of model is known as a “bifactor model”). What works in etiological research, for the purposes of investigating public mental health and in the clinic may well be different
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