Article History
Received: 15 June 2018
Accepted: 22 February 2019
First Online: 4 March 2019
Authors’ information
: Dr. Muller specializes in assessing the quality of life and other patient-reported outcomes of marginalized populations. Dr. Skurtveit is a pharmacoepidemiologist and works with countries across Europe to identify emerging trends of problematic opioid use. Dr. Clausen leads the Norwegian Centre for Addiction Research and advises the EMCDDA and WHO on issues of substance use and healthy ageing.
: The Norwegian Regional Ethics Committee approved the study (ref: 2012/1131/REK). Written informed consent was obtained from all individual participants prior to inclusion into the study.
: Not applicable.
: The authors declare that they have no competing interests.
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