From the Department of Psychological Medicine (B. Chioza, H. Wilkie, Drs. Sham and Makoff) and the Social Genetic and Developmental Psychiatry Research Centre (Drs. Sham and Asherson), Institute of Psychiatry, London; the Department of Neurology (Drs. Nashef and Blower) and the Paediatric Department (Dr. McCormick), Kent and Canterbury Hospital, Canterbury; and Department of Neurology (Dr. Nashef), Kings’ College Hospital, London, UK. (At 2001-05-08)