Received: 5 October 2018
Accepted: 1 May 2019
First Online: 17 May 2019
: AEM researches quality of life among substance-using and other marginalized populations. SS is a senior researcher in pharmacoepidemiology at the Norwegian Institute for Public Health and leads national and Nordic-wide registry-based projects. TC heads the Norwegian Centre for Addiction Research and leads the yearly evaluation of the national opioid maintenance treatment program.
: The Norwegian regional ethics committee approved the study (ref: 2012/1131/REK). Written informed consent was obtained from all patients before participation.
: Not applicable.
: The authors declare that they have no competing interests.
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