OBSESSIVE-COMPULSIVE AND RELATED DISORDERS
These conditions are unified by the presence of obsessions and/or compulsive behaviours that cause functional difficulties in important life domains. Obsessions are recurrent, persistent, intrusive and unwanted thoughts, urges or mental images that lead to marked anxiety or distress. Compulsions are repetitive, intentional behaviours, mental acts or rituals performed in a habitual manner or in response to an obsession to reduce anxiety or discomfort.
Conditions in this group include obsessive-compulsive disorder (OCD), body dysmorphic disorder, hoarding disorder, hair-pulling disorder (trichotillomania) and skin-picking (excoriation) disorder. Although the symptoms of these conditions are relatively diverse, there is increasing scientific evidence of their relatedness to one another.
Although the specific content of obsessions and compulsions varies among individuals with OCD, certain themes are common, including those of cleaning and hygiene, orderliness and symmetry, forbidden thoughts or mental images, and fears of harm to oneself or others.
In body dysmorphic disorder, there is a preoccupation with one or more perceived flaws in one's physical appearance and by repetitive behaviours or mental acts in response to these concerns. The perceived flaws may be mild or not observable by others. Muscle dysmorphia is a form of body dysmorphic disorder characterised by the belief that one's body build is too small or insufficiently muscular.
In hoarding disorder, there is persistent difficulty discarding or parting with possessions, with a strong perceived need to save them and distress associated with discarding them. It is excessive and differs from normal collecting.
Hair-pulling disorder and skin-picking disorder are characterised by recurrent body-focused repetitive behaviours.