1. Hunter Pain Specialists , Broadmeadow, NSW 2292, Australia
2. Genesis Research Services , Broadmeadow, NSW 2292, Australia
3. School of Biomedical Sciences and Pharmacy, College of Health, Medicine and Wellbeing, University of Newcastle , Callaghan, NSW 2308, Australia
4. School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Brain and Mind Centre , Camperdown, NSW 2050, Australia