Funding for this research was provided by:
Thailand Substance Abuse Academic Network (58-B-002)
Received: 28 November 2017
Accepted: 30 April 2018
First Online: 9 May 2018
Ethics approval and consent to participate
: This was an observational study of publicly available data and did not involve human participants. Accordingly, approval from an institutional review board was not required.
: The authors declare that they have no competing interests.
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