Received: 12 September 2017
Accepted: 27 February 2018
First Online: 19 March 2018
: The authors declare that they have no competing interests.
: Not applicable. This study was conducted using secondary data from the Scottish Health Survey. Data are available from the Scottish Health Survey upon reasonable request and with permission of the Information Services Division team from the NHS Scotland. Ethical approval was not required.
: Not applicable.
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