The obsessive-compulsive and related disorders span a range of conditions marked by perseverative thinking and the urge to engage in repetitive behaviours. These disorders include obsessive compulsive disorder (OCD), body dysmorphic disorder (BDD), hoarding disorder, trichotillomania (hair pulling), and excoriation (skin picking). While often comorbid, and having similar maintaining factors and treatment approaches, the underlying distinctions between these disorders include different cognitive distortions, foci of the urges, emotional experiences, and types of behaviour. OCD is the most common of these disorders and is more frequently represented in psychological research studies. The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5; American Psychological Association, 2013) defines these disorders as follows.
OCD is characterised by the presence of obsessions and/or compulsions. Obsessions are defined as recurrent and persistent thoughts, urges, or images that a person experiences as intrusive, unwanted, and distressing. Once experienced, a person will often avoid known triggers of obsessional thinking. However, if triggered, compulsive attempts will be made to ignore, supress, or neutralise such thoughts and urges, and to restore a sense of safety. Compulsions may include overt repetitive behaviours (e.g., cleaning, checking) or covert mental acts (e.g., praying, counting) performed to reduce anxiety or prevent some dreaded outcome, often according to rigid rules. Examples of common obsessions and compulsions are presented in Table 13.1. Many people experience intrusive, unwanted thoughts and engage in the types of behaviours observed in OCD. A diagnosis of OCD requires that the obsessions and/or compulsions are time consuming (e.g., take over 1 hour per day), cause considerable distress, and significantly interfere with an individual's functioning.
BDD, trichotillomania, and excoriation all involve repetitive behaviours about some aspect of the body. BDD involves the preoccupation with a perceived defect or physical flaw that may be unnoticeable or only minimally noticeable to others. Common concerns include imperfect skin, thinning or excessive hair, or that facial features or body parts are too large, too small, or asymmetrical. Individuals with BDD perform repetitive behaviours such as mirror checking, excessive grooming, camouflaging with make-up or clothing, picking at perceived skin defects, and mentally comparing their appearance with others. Trichotillomania and excoriation (respectively) involve compulsive hair pulling and skin picking involving any area of the body.