Which disorder is characterized by a person washing their hands excessively due to intrusive thoughts?

The disorder characterized by excessive hand washing due to intrusive thoughts is obsessive-compulsive disorder (OCD). In individuals with OCD, intrusive thoughts—often referred to as obsessions—can provoke significant anxiety or distress. As a coping mechanism to alleviate the anxiety generated by these thoughts, individuals may engage in compulsive behaviors such as excessive hand washing. This behavior is driven by the belief that it will prevent a feared outcome or reduce anxiety, even when there is no rational basis for such beliefs.

In contrast, dissociative identity disorder involves disruptions in a person's identity and is not centered on compulsive behaviors related to hygiene. Post-traumatic stress disorder is characterized by re-experiencing traumatic events and avoidance of reminders of the trauma. Lastly, conversion disorder involves neurological symptoms that cannot be explained by medical conditions, rather than compulsive behaviors.