[1] Natl Univ Hlth Syst, Dept Pharmacol, Singapore 119074, Singapore
[2] Natl Univ Hlth Syst, Dept Med, Singapore 119074, Singapore
[3] Natl Univ Singapore, Yong Loo Lin Sch Med, Biostat Unit, Singapore 117595, Singapore
[4] Univ New S Wales, Sch Psychiat, Sydney, NSW 2052, Australia