The main characteristic of Obsessive-Compulsive Disorder (OCD) is the presence of obsessions and compulsions. Obsessions are "recurrent and persistent thoughts, urges, or images that are experienced as intrusive and unwanted." Compulsions are "repetitive behaviors or mental acts that an individual feels driven to perform in response to an obsession or according to rules that must be applied rigidly." Obsessions and compulsions take up a significant amount of time out of a person's day (an hour or longer).

DSM-IV Classification: 300.3

ICD-10-CM Classification: F42

(Definition from the Diagnostic and statistical manual of mental disorders: DSM-5)

• Epidemiological research suggests OCD is the fourth most common psychiatric illness
• 2-3 million adults in the United States have OCD
• Females are more likely to be diagnosed with OCD in adulthood
• Males are more likely to be diagnosed with OCD in childhood
• The most common age group for emergence of symptoms is 10-24 years old

(Statistics from the Gale Encyclopedia of Mental Health, 3rd edition)