Funding for this research was provided by:
National Institute on Drug Abuse (R01DA003574)
Received: 21 April 2017
Accepted: 18 July 2017
First Online: 26 July 2017
Ethics approval and consent to participate
: Not applicable: there were no human subjects involved in this commentary.
: Not applicable.
: The author declares that he has no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.