Author Contributions: Ms Cotto had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Volkow, McLellan, Weiss.
Acquisition of data: Cotto, Karithanom, Weiss.
Analysis and interpretation of data: Volkow, McLellan, Cotto, Karithanom, Weiss.
Drafting of the manuscript: Volkow, McLellan, Cotto, Karithanom, Weiss.
Critical revision of the manuscript for important intellectual content: McLellan, Weiss.
Statistical analysis: Cotto, Karithanom.
Study supervision: Volkow, Weiss.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest and none were reported.
Additional Contributions: We kindly acknowledge Ruben Baler, PhD, National Institute on Drug Abuse, for his editorial assistance and critical comments. He did not receive compensation for his contribution besides his salary. This research was carried out at the National Institute on Drug Abuse, National Institutes of Health (NIH).