All of the above studies took place in the United States, where PTSD rates are high; however, 2 studies completed in Europe provided a very different perspective. In Switzerland, Hepp and colleagues¹⁶ assessed the frequency of comorbid PTSD in 277 women with DSM-IV-defined eating disorders, including 84 with anorexia nervosa, 152 with bulimia nervosa, and 41 with eating disorder not otherwise specified using the Structured Clinical Interview for DSM-IV.¹⁶ None of the participants had current PTSD, and only 4 participants (1.4%) met lifetime criteria for PTSD. However, the authors noted that Switzerland has an extremely low base rate of PTSD in the general population. In a Zurich cohort of over 4500 adults, the 12-month prevalence using DSM-IV criteria was found to be 0% for PTSD, 2.2% for subthreshold PTSD in females, and 0.26% for subthreshold PTSD in males.¹⁷

In a study undertaken in Great Britain, 164 consecutive referrals to the Eating Disorders Unit at the Maudsley Trust Hospitals who met criteria for anorexia nervosa (n = 90), bulimia nervosa (n = 54), or eating disorder not otherwise specified (n = 20) were assessed for PTSD using the Structured Clinical Interview for DSM-III-R.¹⁸ In the overall sample only 4% met criteria for current PTSD and 11% met criteria for lifetime PTSD. Patients with anorexia nervosa had PTSD rates (10%) similar to those of patients with bulimia nervosa (13%) and those who had eating disorder not otherwise specified (10%).

Reasons for a link
The potential reasons for an association between severe trauma, PTSD, and bulimic disorders, especially bulimia nervosa, have been discussed in detail elsewhere.^2,5,8,9 It has been hypothesized that eating disordered behaviors, particularly purging behaviors, serve to facilitate avoidance of traumatic material and to numb the hyperarousal and emotional pain associated with traumatic memories and thoughts. Purging may also promote forgetting parts or all of a traumatic event (ie, dissociative amnesia). Several studies have reported higher rates of dissociative symptoms in bulimic patients than in controls, and in the National Women's Study, 27% of patients with bulimia nervosa endorsed forgetting all or part of traumatic memories compared with 11% of participants who did not have an eating disorder.⁸ Thus, bulimia often serves as a maladaptive coping strategy in the same way substance abuse does in relationship to trauma and PTSD.^2,3,19

Treatment
Treatment approaches for PTSD and trauma-related disorders have advanced considerably over the past several years. The most empirically validated treatments for PTSD include cognitive-behavioral therapy (CBT) with prolonged exposure (PE), eye movement desensitization reprocessing (EMDR), and pharmacotherapy,^20-25 although CBT with PE appears to be the most effective and long-lasting modality. Psychodynamic psychotherapy that involves the processing of traumatic material may also be useful.^24,26 Dialectical behavior therapy can be effective in BPD and other trauma-related diagnoses characterized by affective dysregulation, including PTSD, bulimia nervosa, impulse control disorders, and dissociative disorders.^23,25,27-31

There are no published treatment studies or guidelines specifically involving patients with eating disorders and PTSD. The principles of treatment for such patients are based on practice guidelines for the individual conditions. The American Psychiatric Association has published guidelines for both eating disorders and PTSD. An attempt to combine these principles into an integrated approach for the traumatized patient with a comorbid eating disorder has been detailed elsewhere.^2,5 In addition, a case formulation approach has been described that can be used to integrate empirically supported treatments for various comorbid conditions, including PTSD and eating disorders.^32,33

In the case formulation approach, the clinician applies hypotheses about potential mechanisms that cause and perpetuate dysfunctional behaviors. This is combined with the adoption of empirically validated treatments for each case that includes hypothesis testing and continuous collection of data to assess progress and process. A critical component of this approach is to determine the functional mechanisms that link problem behaviors or disorders.² In other words, what is the function of the symptom? For example, a common hypothesis is that bulimic behaviors, such as self-induced vomiting and laxative abuse, act to facilitate or promote numbing and avoidance of trauma-related memories, dreams, feelings, thoughts, and behaviors, and decrease or blunt associated hyperarousal.

To the degree that this theory is verified by the patient, this makes way for learning healthier coping strategies to effectively deal with the underlying issues without the adverse consequences. In this integrated line of attack, evidence-based treatments for eating disorders, such as CBT for PTSD, can be woven into a phasic deployment of interventions that are modified to the needs of the individual.