Obsessive-compulsive disorder
Obsessive–compulsive disorder (OCD) is an anxiety disorder
Anxiety disorder
Anxiety disorder is a blanket term covering several different forms of abnormal and pathological fear and anxiety. Conditions now considered anxiety disorders only came under the aegis of psychiatry at the end of the 19th century. Gelder, Mayou & Geddes explains that anxiety disorders are...

 characterized by intrusive thoughts
Intrusive thoughts
Intrusive thoughts are unwelcome involuntary thoughts, images, or unpleasant ideas that may become obsessions, are upsetting or distressing, and can be difficult to manage or eliminate. Most people experience these thoughts...

 that produce uneasiness, apprehension, fear, or worry, by repetitive behaviors aimed at reducing the associated anxiety, or by a combination of such obsessions and compulsions
Compulsive behavior
Compulsive behavior is behavior which a person does compulsively—in other words, not because they want to behave that way, but because they feel they have to do so....

. Symptoms of the disorder include excessive washing or cleaning; repeated checking; extreme hoarding
Compulsive hoarding
Compulsive hoarding is the acquisition of possessions in excess of socially normative amounts, even if the items are worthless, hazardous, or unsanitary...

; preoccupation with sexual
Sexual obsessions
Sexual obsessions are obsessions with sex, and in the context of obsessive-compulsive disorder these are extremely common . It can become extremely debilitating, making the sufferer ashamed of the symptoms and reluctant to seek help. Preoccupation with sexual matters, however, does not only occur...

, violent or religious thoughts; aversion to particular numbers; and nervous rituals, such as opening and closing a door a certain number of times before entering or leaving a room.