Funding for this research was provided by:
National Institute on Drug Abuse (P50DA035763)
First Online: 7 August 2019
Compliance with Ethical Standards
: On behalf of all authors, the corresponding author states that there is no conflict of interest.
: All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation [institutional and national] and with the Helsinki Declaration of 1975, as revised in 2000. Informed consent was obtained from all participants for being included in the study.