Dan always returns after leaving home to see if he locked the door. he always locks the door, but he thinks about whether or not he locked the door until he has checked. dan's behavior is an example of (2007, 8)

Obsessive-Compulsive Disorder (OCD)

Explanation:

Mental disorder of these recurring (thoughts)obsessions and repetitive (behaviors) compulsions in long lasting periods of time if not all life long; asa result this person could have long lasting effect if not short or long term consequences.