1. Department of Psychiatry, University of Melbourne, and St Vincent's Mental Health Service, P.O. Box 2900, Fitzroy, Victoria, 3065, Australia
2. Department of Psychiatry, University of Melbourne and North-Western Mental Health, Centre for Psychosocial Research and Policy, Melbourne, Australia
3. Department of Psychiatry, University College Hospital, Ibadan, Nigeria
4. Department of Mathematics and Statistics, The University of Melbourne, Victoria, Australia