As previously mentioned, the disorders in the OCRDs category have both similarities and differences. Specifically, people with obsessive-compulsive disorder (OCD) and body dysmorphic disorder (BDD) both experience recurrent, time-consuming, intrusive, and unwanted thoughts. These thoughts cause a lot of anxiety and other strong emotions such as disgust, depression, and shame. The compulsive behaviors in OCD and BDD both serve to reduce anxiety and/or "regulate" other negative emotions such as disgust. However, BDD compulsions may have a greater emotional regulation function, rather than anxiety reduction as with OCD. This difference affects treatment selection. Therapies that are effective for reducing the anxiety associated with obsessions (such as ERP) may be less effective when it comes to other emotions such as disgust.
Another similarity and difference between OCD and BDD concerns insight. Like OCD, the diagnosis of BDD includes an insight specifier to further refine the diagnosis. While people with both disorders have inaccurate or irrational beliefs, they differ in terms of whether or not they recognize this fact. For instance, some people with BDD readily recognize and accept their concern with their appearance is excessive and unrealistic. Nonetheless, this insight does not diminish their preoccupation and resulting behaviors. Other people lack this insight. They firmly cling their distorted beliefs, despite evidence that refutes the validity of such beliefs. For instance, Gina refused to believe the dermatologist's assessment that her acne condition was mild. This lack of insight is important with respect to treatment. In general, people with poor or absent insight have a poorer prognosis for a full and complete recovery.
While both OCD and BDD have insight specifiers, people with BDD tend to have poorer insight than people with OCD. In fact, only 2% of people with OCD have a delusional/absent degree of insight while 27-60% of people with BDD have a comparable degree of insight (Phillips et al. 2007; Eisen, Phillips, Coles, & Rasmussen 2004; Phillips et al., 2006; Mancuso, Knoesen, & Castle 2010). Subsequently, people with BDD may be less likely to believe that their symptoms and beliefs are "irrational." Therefore, they may be less motivated for treatment. This difference has important implications for treatment selection. Although exposure and response prevention therapy (ERP) is a highly effective treatment for OCRDs, people with BDD may need to precede ERP with a cognitive reconstructing approach aimed at challenging BDD beliefs. Likewise, motivational strategies may be useful to improve desire and commitment to therapy and recovery.
In addition to similar symptom presentation, OCD and BDD have high comorbidity rates. Simply stated, this means there is greater likelihood that someone with OCD may also have BDD when compared to someone with neither disorder. Moreover, these disorders are more common in first-degree relatives. This suggests that someone with BDD or OCD is more likely to have a first-degree relative with one or both of these disorders.