Psychiatric Comorbidity Among Eating Disorders and Obsessive-Compulsive Disorder and Underlying Shared Mechanisms and Features: An Updated Review.

Eating disorders (EDs) are highly comorbid with obsessive-compulsive disorder (OCD), with comorbidity rates as high as 41%. In the current review, we summarize the literature regarding the prevalence of ED-OCD comorbidity. We also identify and review the literature assessing shared features (i.e., shared characteristics or symptoms) and mechanisms (i.e., variables that may explain ED or OCD symptoms) of EDs and OCD. Potential shared features of EDs and OCD include age of onset, course of illness, obsessions, compulsions and ritualistic behaviors, and thought action fusion. Shared mechanisms that may explain ED-OCD comorbidity include genetic and neurobiological mechanisms, anxiety and fear, repetitive negative thinking, perfectionism, intolerance of uncertainty, distress tolerance, and impulsivity. Based on these shared features and mechanisms, a theoretical conceptualization of ED and OCD comorbidity is developed, and outline considerations for assessment, differential diagnosis, treatment, and future research regarding ED-OCD comorbidity are described.

Obsessions are strongly related to eating disorder symptoms in anorexia nervosa and atypical anorexia nervosa.

Anorexia nervosa (AN) and obsessive-compulsive disorder (OCD) are highly comorbid. However, little research has examined which specific cognitive-behavioral aspects (e.g., checking, obsessing) of OCD are most relevant in those with AN. Furthermore, there is no research examining aspects of OCD in Atypical AN. The current two studies (N = 139 and N = 115 individuals diagnosed with AN/Atypical AN) examined a) which aspects of OCD were most related to AN symptomatology and b) if there were differences in OCD between individuals diagnosed with AN vs Atypical AN. We found that obsessing was most related to AN symptoms. We also found that there were no substantial significant differences between AN and Atypical AN. These findings add to the literature suggesting minimal differences between AN and Atypical AN, specifically regarding OCD symptomatology. These findings clarify that obsessions (rather than compulsions) may be the specific aspect of OCD most warranting treatment intervention in AN and Atypical AN.