The vast majority of patients seeking treatment for an eating disorder do not meet full DSM criteria. What are the implications for diagnosis and treatment of eating disorders?
What are the broader implications for categorical versus dimensional perspectives on the diagnosis of mental illness?
The American Psychiatric Association’s (APA) Diagnostic and Statistical Manual of Mental Disorders (DSM) is a handbook of written guidelines that primarily focuses on the classification of mental disorders rather than the mental disorders itself. It is used in the prevention, management and assessment of a patient’s mental state. Aside from this, it is also serves to provide as a common ground for researchers to work on, to study the criteria to further improve it for future DSM revisions. In clinical practice and research, the DSM’s role is facilitated by its classification system; usually either categorical or dimensional in approach (4th ed., text rev.; DSM–IV–TR; American Psychiatric Association, 2000; Kraemer, 2007). The categorical approach is the assessment of either a positive or negative diagnosis based on a strict set of standardised criteria. Conversely, the dimensional approach is a more relaxed approach than the categorical, where it involves the classification of mental disorders by quantifying a person’s symptom and representing them with numerical values on one or more scales. It concerns the degree of presence of the mental disorder apparent within the patient, rather than the actual presence; that is, how much of the criteria does the patient correspond with. The higher the scores on the scores of the scales the more likelihood the patient has the disorder. For instance, higher scores on the Hamilton Depression scale, a seven point Likert scale, will indicate a higher chance the patient is depressed (Brown & Barlow, 2005). As recognised by Brown and Barlow, there is a potential positive implication of adopting a DSM with an increasingly dimensional approach. However, there is a continual debate regarding the categorical and dimensional perspectives of diagnosis. This is especially present with the richly dimensional oriented DSM-V (5th ed.; DSM–5; American Psychiatric Association, 2013; Machado, Goncalves & Hoek, 2013; Regier, Kuhl, & Kupfer, 2013). Throughout this paper, the broad implications of this continual debate will be discussed, following by the investigation of the implications for patients who do not meet the full DSM Eating Disorder criteria.
A patient has a higher chance of being diagnosed with depression if they score higher a patient scores on the Hamilton Depression scale, a seven point Likert scale, the higher the likelihood they are depressed (Brown & Barlow, 2005).
Throughout the various version of the DSM, its use the categorical approach requires the acknowledgement that there are heterogeneous factors among disorder populations that are not within the diagnosis (4th ed., text rev.; DSM–IV–TR; American Psychiatric Association, 2000). As a result of this, there are high levels of co-morbid positive diagnoses – 79% of lifetime mental disorders are observed in people with at least one diagnosed mental disorder (Kessler, Chiu, Delmer & Walters, 1994; Krueger, & Bezdjian, 2009). From this, an implication of a categorical approach can be deduced; that is, positively diagnosed patients should be assigned standardised treatments that are not necessarily aimed at only treating them due to heterogeneous factors such as co-morbidity. The dimensional approach, however, utilises more clinical information about the heterogeneous factors that are present in patients (Brown & Barlow, 2005). The implication formed here for the dimensional approach would be assignment of various appropriate treatments that would be deemed most effective for the respective patient, as there is sufficient clinical information regarding the patient’s varying dimensions.
Additionally, with regards to the categorical approach, the lack of presence of a single criterion for a particular mental disorder in the DSM can ultimately determine a positive or negative diagnosis. Consequently, the forms large residual undefined categories, such as the Eating Disoder – Not Otherwise Specified (EDNOS) category, where it is a category aimed for patients who do not meet the full criteria for anorexia nervosa, bulimia nervosa or binge eating disorder (that was introduced in the DSM-V) (5th ed.; DSM–5; American Psychiatric Association, 2013; Machado, Goncalves & Hoek, 2013). Due to the nature of the dimensional approach, quantifying dimensions of disorders, it will help reduce the formation of large residual categories, thus, can be seen as an implication of the dimensional approach (Brown & Barlow, 2005). Hence, patients have less of chance being diagnosed into the residual category of mental disorder under a classification system that priorities the recognition of presenting criterion, even though they do not satisfy the fixed diagnostic criteria of a categorical classification approach.
The dimensional approach makes use of one or more scales to measure particular dimensions of various mental disorders. This can be seen as a potential positive implication for clinical practice and research (Lopez, Compton, Grant & Breiling 2007). Initially, Kraemer (2007) found that the categorical approach is most beneficial to clinical practitioners, whilst the dimensional approach is most beneficial to researchers. However, Lopez et al. (2007) came to realise that clinical practitioners would also come to benefit from the growing popularity of dimensional orientation, since the changes in severity of a mental disorder and its dimensions could be quantitatively measured by fluctuations in multi-ordinal scales. Hence, proving to be more informative than measuring responses to interventions by comparing the fluctuations between the borderlines of a positive and negatives diagnosis, as in a categorical approach.
Moreover, this implication relates to how an improvement of research outcomes would be apparent through the adoption of a increasingly dimensional approach.
Unfortunately, there are many associated negative implications of adopting a more dimensional approached, which are apparent with the difficulties of changing an existing classification system (First, 2005). With the increase popularity of the use of the dimensional approach, similar to the direction and development of research of the DSM-V, there would be an apparent difficulty in merging past and present research to reach conclusions about present studies (First, 2005; Reiger, Kuhl & Kupfer, 2013; 5th ed.; DSM–5; American Psychiatric Association, 2013). Moreover, issues will arise in the clinical use of the DSM, resulting practitioners to revise their diagnoses of existing patients as well as their practice with new patients. Lopez et al. (2007) also outlined a complication of the diagnostic criteria of earlier DSMs, where most were in favour of the dimensional approach, will be present as there will be a varying abilities of different psychiatric disorders to be measured dimensionally. They highlighted this with comparison between dimensional approach adapted to psychoses obtained from a scarce literature and a dimensional approach for substance use disorder obtained from a supportive literature. Thus, concluding that the shift from categorical classifications approaches to dimensional approaches will be difficult in the future.
The implications of categorical approaches of diagnosing mental disorders are evident through the concern with the diagnoses of eating disorders. One of these implications is the large residual EDNOS category. The majority of individuals who seek treatment for eating disorders are diagnosed with EDNOS. Due to the strict nature of the criteria of eating disorders, patients being negatively diagnosed due to not fulfilling the criteria; only having partial eating disorders like partial anorexia nervosa and partial bulimia nervosa, resulting an increase in the EDNOS category. The implication here would be a demand for treatment from an excessively heterogeneous population diagnosed with EDNOS. However, practitioners are at risk in having no solution or intervention to use, due to the EDNOS category lacking homogenous characteristics which are required to determine research-based effective treatments.
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