The question of whether mental disorders are discrete clinical conditions or arbitrary distinctions along dimensions of functioning is a long-standing issue, but its importance is escalating with the growing recognition of the frustrations and limitations engendered by the categorical model. The authors provide an overview of some of the dilemmas of the categorical model, followed by a discussion of research that addresses whether mental disorders are accurately or optimally classified categorically or dimensionally. The authors' intention is to document the importance of this issue and to suggest that future editions of the Diagnostic and Statistical Manual of Mental Disorders give more recognition to dimensional models of classification. They conclude with a dimensional mental disorder classification that they suggest provides a useful model.
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"Underlying current classification systems of mental disorders, the Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5; American Psychiatric Association, 2013) and the International Statistical Classification of Diseases, 10th revision (ICD-10; World Health Organization, 1992), is the view that psychopathology is best assessed in a categorical manner, essentially as phenomenological entities made distinct from normality by the presence and severity of their individual constellation of symptoms. In contrast to this position, however, several theorists have contended that mental illnesses are more accurately assessed as dimensional phenomena, with differences between individuals being a matter of degree rather than of type (Flett et al. 1997; Widiger & Samuel, 2005; Helzer et al. 2006; Widiger & Edmundson, 2014). Empirical research is required directly to delineate the latent structure of depression, and thereby to inform the ongoing theoretical debate regarding the nosology of this disorder (Sonuga-Barke, 1998; Beauchaine, 2003). "
[Show abstract][Hide abstract] ABSTRACT: Background:
A basic phenomenological question of much theoretical and empirical interest is whether the latent structure of depression is dimensional or categorical in nature. Prior taxometric studies of youth depression have yielded mixed findings. In a step towards resolving these contradictory findings, the current taxometric investigation is the first to utilize a recently developed objective index, the comparison curve fit index, to evaluate the latent structure of major depression in an epidemiological sample of children and adolescents.
Data were derived from Mental Health of Children and Young People in Great Britain surveys. Participants were administered a structured diagnostic interview to assess for current depression. Parents (n = 683) were interviewed for children aged 5-16 years, and child interviews (n = 605) were conducted for those aged 11-16 years.
MAMBAC (mean above minus below a cut), MAXEIG (maximum eigenvalue) and L-Mode (latent mode) analyses provided convergent support for a dimensional latent structure.
The current findings suggest that depression in youth is more accurately conceptualized as a continuous syndrome rather than a discrete diagnostic entity.
Full-text · Article · Feb 2016 · Psychological Medicine
"examined as separate disorders in comorbidity studies, it has been suggested that the distinction between anxiety and depression is artificial and solely due to limitations engendered by a categorical model of disorder (Widiger & Samuel, 2005). For example, GAD and MDD share the common symptom of fatigue (APA, 2013;Zinbarg et al., 1994) and irritability in children (APA, 2013). "
[Show abstract][Hide abstract] ABSTRACT: Background: Comorbidity of anxiety and depression predicts impaired treatment outcomes, poor quality of life and increased suicide risk. No study has reported on a combined measure of anxiety-depression in boys with an Autism Spectrum Disorder. Aims: To explore the prevalence, underlying factor structure and relationships between anxiety-depression, physiological stress and symptoms of Autism Spectrum Disorder (ASD). Methods: 150 boys (aged 6-18 years; IQ M= 94.9, range. = 73-132) with an ASD plus their parents (135 mothers, 15 fathers) completed scales about the boys' anxiety and depression, and the boys provided samples of their saliva in the morning and afternoon. Parents also completed the ASD Behaviour Checklist about the boys' ASD symptoms. Results: The two sources of ratings were not significantly different for prevalence of anxiety-depression but the factor structures varied between the parents' and boys' responses, with a four-factor solution for the boys' ratings and a three-factor solution for the parents' ratings. There were also differences in the correlations between cortisol and anxiety-depression and between ASD symptoms and anxiety depression across the boys' and parents' data. Conclusions: Assessment of anxiety and depression comorbidity from parents and from children with an ASD themselves could provide a valuable adjunct datum when diagnosing ASD.
Full-text · Article · Feb 2016 · Research in developmental disabilities
"For the structural analyses, we used a dimensional approach to AvPD, constructing variables based on the number of endorsed criteria. Dimensional representations are often considered a better conceptualization of personality disorders than categorical diagnoses (Widiger & Samuel, 2005). To optimize statistical power, we used the number of subthreshold criteria (≥1), assuming that the risk for each trait was continuous and normally distributed, i.e., that the classification (0–3) represented different degrees of severity. "