Acknowledgements
The authors thank the study participants for their contribution to the research, as well as current and past researchers and staff of the OPTIMA Research Group within the Canadian Research Initiative in Substance Misuse. The authors would also like to thank the EuroQol Research Foundation for funding to cover the Open Access fee. This funding was applied for after the manuscript had been accepted for publication; the EuroQol Research Foundation had no involvement in any other aspect of the study.