Article History
Received: 12 July 2018
Accepted: 1 October 2018
First Online: 16 October 2018
Compliance with ethical standards
:
: The authors declare that they have no competing interests.
: This study was approved by the Regional ethics committee of Gothenburg, Sweden 2013 (399-13).
: Written informed consent was obtained from all study subjects at the youth clinic at the time of inclusion in the study.