My Son's Friend (24 Year Old Male) Tearfully Confided In

My son's friend (24 year old male) tearfully confided in me that he has numbness from his lower penis to his anus. He is terribly distressed about it. Specialist he went to said it was in his head. He has been dealing with this for several years and it affects his ability to have relationships. What could be the cause ofvthis?