A 15 year old boy feels that the di has hung onto him whenever he passes through the diy 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 the di and contamination. This has affected his studies also. The most likely diagnosis is :
Agoraphobia Conduct disorder Adjustment disorder Obsessive compulsive disorder