Obsessive compulsive disorder (OCD) is characterised by a person experiencing obsessions, defined as recurrent, persistent thoughts, impulses and urges that lead to distress or anxiety, and/or compulsions, defined as repetitive and excessive behaviours that the individuals feel they must perform in order to reduce anxiety or to prevent some dreaded outcome from occurring.

Symptoms can last for more than an hour each day and will interfere with daily functioning and can often lead to significant distress and impairment in social, occupational or other areas of functioning. OCD typically manifests in different forms, with the most common obsessions and compulsions falling into the categories of checking, contamination, hoarding, intrusive thoughts, and symmetry and ordering.