Funding for this research was provided by:
Thailand Substance Abuse Academic Network (58-B-002)
Text and Data Mining valid from 2018-05-09
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.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.