Funding for this research was provided by:
National Institute on Drug Abuse (K01-DA039030, R21-DA039019)
First Online: 14 September 2017
Compliance with Ethical Standards
: The authors declare that they have no conflict of interest.
: All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards.
: Informed consent was obtained from all individual participants included in the study.