Carrying out the compulsion reduces the anxiety, but makes the urge to perform the compulsion stronger each time it recurs, reinforcing the intrusive thoughts. Intrusive thoughts can occur with or without compulsions. How people react to intrusive thoughts may determine whether these thoughts will become severe, turn into obsessions, or require treatment.

Distinguishing them from normal intrusive thoughts experienced by many people, the intrusive thoughts associated with OCD may be anxiety provoking, irrepressible, and persistent. The thoughts may become obsessions that are paralyzing, severe, and constantly present, these might involve topics such as violence, sex, or religious blasphemy, among others. Attempting to suppress intrusive thoughts often cause these same thoughts to become more intense and persistent. When intrusive thoughts occur with obsessive-compulsive disorder (OCD), patients are less able to ignore the unpleasant thoughts and may pay undue attention to them, causing the thoughts to become more frequent and distressing. Such thoughts are universal among humans, and have 'almost certainly always been a part of the human condition'. Psychologist Stanley Rachman presented a questionnaire to healthy college students and found that virtually all said they had these thoughts from time to time, including thoughts of sexual violence, sexual punishment, 'unnatural' sex acts, painful sexual practices, blasphemous or obscene images, thoughts of harming elderly people or someone close to them, violence against animals or towards children, and impulsive or abusive outbursts or utterances. For most people, intrusive thoughts are a 'fleeting annoyance'.

Many people experience the type of negative and uncomfortable thoughts that people with more intrusive thoughts experience, but most people can dismiss these thoughts. Intrusive thoughts, urges, and images are of inappropriate things at inappropriate times, and generally have aggressive, sexual, or blasphemous themes. Intrusive thoughts may also be associated with episodic memory, unwanted worries or memories from OCD, post-traumatic stress disorder, other anxiety disorders, eating disorders, or psychosis. When such thoughts are associated with obsessive-compulsive disorder (OCD), Tourettes syndrome (TS), depression, body dysmorphic disorder (BDD), and sometimes attention-deficit hyperactivity disorder (ADHD), the thoughts may become paralyzing, anxiety-provoking, or persistent. An intrusive thought is an unwelcome, involuntary thought, image, or unpleasant idea that may become an obsession, is upsetting or distressing, and can feel difficult to manage or eliminate.

Lingering thoughts synonym