1. Department of Anaesthesia, University of Otago, Christchurch, Corner of Riccarton and Hagley Avenues, Christchurch 8042, New Zealand
2. Department of Population Health, University of Otago, Christchurch, Corner of Riccarton and Hagley Avenues, Christchurch 8042, New Zealand
3. Department of Psychological Medicine, University of Otago, Christchurch, Corner of Riccarton and Hagley Avenues, Christchurch 8042, New Zealand