Police are appealing for information to locate 42-year-old Steven McLoughlin from Milton Keynes.
Steven absconded from Marlborough House in Standing Way, at around 9.30am on Wednesday (August 8), when he failed to return following a period of unescorted leave.
Steven is white, approximately 6ft 2ins tall, has a large build, is bald and clean shaven.
He was last seen wearing a black bomber jacket, a grey hooded top with a black hood, grey jogging bottoms and Airwalk trainers.
Steven is known to frequent London and it is believed he has since travelled to London.
Superintendent Yvette Hitch said: “We are concerned for Steven and are appealing for information from the public to help to locate him.
“If you see him do not approach him but instead contact police on 999 if you see someone matching his description.
“We are concerned as he is without medication which he requires. Officers are carrying out extensive enquiries, including CCTV enquiries and working with other forces, in our efforts to find him to ensure he receives medical care.”