Dexter Elliott was last seen leaving his Worksop home, at about 4pm on Thursday 12th December 2013 but he did not return home.
He is white and about 5ft 5ins tall. He has shaven dark hair, brown eyes, and is of a medium build and has a Yorkshire accent.
He was last seen wearing a dark woolly hate, jeans, a black jacket and trainers.
Police are growing increasingly concerned as Mr Elliott has now gone four days without medication.
Anyone who has seen Mr Elliott or knows of his whereabouts should contact Nottinghamshire Police on 101 or call Crimestoppers anonymously on 0800 555 111.