Psychiatric comorbidity, or dual-diagnosis, is a common issue for those with an eating disorder. Clinical and community studies have reported that between 55% and 98% of individuals with anorexia nervosa and between 88% and 97% of individuals with bulimia nervosa meet the criteria for another psychiatric disorder (Hughes, et al., 2013).
The most common disorders to co-occur with an eating disorder are; mood, anxiety, substance use, and personality disorders. Studies suggest that different kinds of disorders may interact with eating disorders differently.
Some studies have found that early-onset anxiety disorders may represent a genetically-based pathway toward the development of an eating disorder. This has stemmed from the idea that excessive fear about certain events or situations may lead into excessive concerns about eating, shape and weight, and subsequently lead into the development of disordered eating behaviours (Pallister & Waller, 2008).
This is in contrast with research showing that obsessive-compulsive disorder, generalised anxiety disorder, post-traumatic stress disorder, and panic disorder typically occur simultaneously with or following the onset of the eating disorder (Kaye, Bulik, Thornton, Barbarich, & Masters 2004). These findings suggest that eating disorders may exacerbate anxiety symptoms. In particular, the effects of starvation and other weight-loss methods can contribute to obsessive-compulsive behaviours related to food, eating and body-checking.
The effects of starvation may also contribute to depressive symptoms or even the onset of a depressive disorder. Studies of the onset of eating disorders and depression suggest that eating disorders tend to precede the development of depression, and that depressed mood improves with weight restoration (Hughes, et al., 2013). Co-morbid depression may predict a longer course of illness or contribute to the development and intensity of eating disorder symptoms. It is also possible that depressed individuals are more likely to experience their eating disorder symptoms as distressing, or to more readily communicate their distress.
A trans-diagnostic approach to understanding comorbidity may offer a simplistic explanation for co-morbid diagnoses. This approach suggests that shared personality traits or underlying neuro-cognitive processes play a key role in the mediation and maintenance of eating disorder and co-morbid symptoms (Pollock & Forbush, 2013).
Regardless of the course of their development, when eating disorder symptoms do co-occur with other mental health disorders it affects a wide range of functions for each person.
Several studies have reported that individuals with eating disorders and co-morbid diagnoses are more likely to have a poorer prognosis; increased social and psychosocial impairment, decreased health-related quality of life, higher rates of mortality and a more chronic course of illness (Bodell, Brown, & Keel, 2012; Hughes, et al., 2013; Pollock & Forbush, 2013). This link to outcomes may be because the effects of comorbidity hamper recovery, or because the presence of additional mental health issues represents increased severity and complexity of illness.
Individuals with co-morbid diagnoses are more likely to seek treatment than those with a single diagnosis, and yet these patients are often excluded from outcome trials and treatment programs because of the complexity of their presenting problems. Those who seek help frequently only present with one diagnosis, which may leave these complicated cases at risk for medical problems associated with their diagnoses (Courbasson, Nishikawa, & Dixon, 2012). Integrated treatment for clients presenting with an eating disorder and co-morbid psychiatric condition may be a valuable approach.
Comorbidity may complicate the diagnostic picture and treatment process either directly, or as a function of the eating disorder severity. It may be beneficial for treatments to take into account specific areas of functioning being impaired. Determining the priority of symptoms to be treated may depend in part on the onset of the disorders.
Understanding the mechanisms that underlie the co-occurrence between these disorders is of importance, as it may contribute to a better understanding of the development and progression, and aid in the design of new treatments to target shared underlying mechanisms of dysfunction.
Despite empirical evidence for the high rates of comorbidity for those with an eating disorder, clinicians often find making treatment decisions for these individuals very difficult. There continues to be confusion about the best course of assessment and treatment in the presence of more than one diagnosis at one time.
There is a clear need for research investigating comorbidity in order to ensure further assessment and treatment of these disorders.
Bodell, L. P., Brown, T. A., & Keel, P. K. (2012). The Impact of Bulimic Syndromes, Mood and Anxiety Disorders and Their Comorbidity on Psychosocial Impairment: What Drives Impairment in Comorbidity? European Eating Disorders Review, 20(1), 74-79.
Courbasson, C., Nishikawa, Y., & Dixon, L. (2012). Outcome of Dialectical Behaviour Therapy for Concurrent Eating and Substance Use Disorders. Clinical Psychology & Psychotherapy, 19, 434-449.
Hughes, E. K., Goldschmidt, A. B., Labuschagne, Z., Loeb, K. L., Sawyer, S. M., & Grange, D. L. (2013). Eating Disorders with and without Comorbid Depression and Anxiety: Similarities and Differences in a Clinical Sample of Children and Adolescents. European Eating Disorders Review, 21(5), 386-394.
Kaye, W. H., Bulik, C., Thornton, L., Barbarich, N., & Masters, K. (2004). Comorbidity of anxiety disorders with anorexia and bulimia nervosa. The American Journal of Psychiatry, 161(12), 2215-2221.
Pallister, E., & Waller, G. (2008). Anxiety and eating disorders: understanding the overlap. Clinical Psychology Review, 28, 366-386.
Pollack, L. O., & Forbush, K. T. (2013). Why do eating disorders and obsessive–compulsive disorder co-occur? Eating Behaviors, 14(2), 211-215.
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