The idea of a spectrum of disorders with obsessive-compulsive features is nothing new. Indeed, evidence spanning over a 20-year period has continued to accumulate. This research supports the theoretical and clinical utility of grouping these disorders together. As research continues, the types of disorders included in this group may change. Moreover, our understanding of this obsessive-compulsive spectrum will continue to be refined.
The Diagnostic and Statistical Manual of Mental Disorders- Edition 5 (DSM-5; APA, 2013) places these disorders into a category called obsessive-compulsive and related disorders (OCRDs). The DSM-5 is a manual used by mental health professionals to diagnosis mental disorders. The primary purpose of the DSM-5 is to help clinicians reliably identify and diagnose various mental disorders.
Each disorder in the DSM-5 includes a list of symptoms associated with that disorder. The manual also includes additional features of the disorder (e.g., age of onset, family history, etc.). It further provides criteria for distinguishing the disorders from each other. This is particularly important as many mental disorders share similar symptoms. Accurate diagnosis aids clinicians to identify which people may benefit from treatment. Perhaps more importantly, it helps clinicians select the most effective treatment approach. Just as there are many cancers with different methods of effective treatments, so too are there many mental disorders with different forms of effective treatments.
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The following disorders are included in the DSM-5 category called obsessive-compulsive and related disorders category (OCRDs):
- obsessive compulsive disorder (OCD);
- body dysmorphic disorder (BDD);
- hoarding disorder;
- trichotillomania (hair pulling); and,
- excoriation (skin picking) disorder.
In addition, several other "lower order" disorders are included in this category:
- substance/medication-induced obsessive-compulsive related disorder;
- obsessive-compulsive and related disorder due to another medical condition;
- other specified obsessive and compulsive and related disorders; and,
- unspecified obsessive-compulsive and related disorders (such as body-focused repetitive behavior disorder and obsessional jealousy).
Decisions about which disorders are grouped together in the DSM-5 are based on whether there is some underlying relationship between two or more disorders. In other words, do these disorders have something in common with each other? With respect to mental disorders, there are several things that suggest a similarity between disorders. Some examples are: symptom similarity; frequency of co-occurrence (called comorbidity); the onset and usual pattern of the disorder; genetic risk factors; environmental risk factors; neural substrates, biological markers; and treatment response. To date, the strongest evidence for similarities among the OCRDs comes from symptom similarity, as well as the high degree of co-occurrence (comorbidity) among the disorders.
It is interesting to note the rationale used to organize the entire DSM-5 manual is similar to the rationale used for grouping the obsessive-compulsive and related disorders (OCRDs) together. For example, the chapter on anxiety disorders precedes the chapter on OCRDS. The purpose behind this placement is to inform clinicians there is a similarity between anxiety disorders and OCRDs. While anxiety is a key feature in OCRDs, there are enough unique differences between anxiety disorders (e.g., panic disorder, social phobia) and OCRDs to justify a separate category.
To recap, the hallmark features of OCRDs are repetitive thoughts, distressing emotions, and compulsive behaviors. Although there is symptom similarity and overlap, each disorder has its own unique features. These differences affect treatment decisions in several ways: 1) the choice of treatment type; 2) the ordering, and pacing of therapeutic interventions; and, 3) setting realistic goals and expectations for clinicians, patients, and family members about treatment progress. These differences are discussed in the treatment section.
In the next section, we describe the diagnostic criteria for OCRDs. We also compare and contrast the disorders to highlight their similarities and differences.