A 15 year old boy feels that the dirt has hung onto him whenever he passes through the dirty street. This repetitive thought causes much distress and anxiety. He knows that there is actually no such thing after he has cleaned once but he is not satisfied and is compelled to think so. This has led to social withdrawal. He spends much of his time thinking about dirt and contamination. This has affected his studies also. The most likely diagnosis is -
In this question, the patient is presenting with classical features of OCD:-
Recurrent unwanted thoughts of dirt and contamination, i.e. obsession.
The thought is recognized as irrational and absurd (patient knows that there are no such things)
Irresistible thought causing marked distress and anxiety
Compulsion for cleaning
Obsessive compulsive disorder
Conduct disorder
Agoraphobia
Adjustment disorder