Marees Th Derksen1, M J W Vreeling2, Ilja Tchetverikov3. 1. Department of Psychiatry, Albert Schweitzer Hospital, Dordrecht, The Netherlands. 2. Department of Psychiatry, Albert Schweitzer Hospital, Dordrecht; and Yulius, Mental Health Institute, Dordrecht, The Netherlands. 3. Department of Rheumatology, Albert Schweitzer Hospital, Dordrecht, The Netherlands.