World ___ Awareness Day (April 2) (6)
I believe the answer is:
autism
(Other definitions for autism that I've seen before include "Mental condition where sufferer withdraws into private world of fantasy" , "Condition involving impaired social interaction" , "Condition characterized by difficulty in communicating and forming relationships" , "Mental illness that isolates from the real world" , "Form of mental illness causing one to withdraw into private world" .)