He later earned a postdoctoral diploma in alcoholism early intervention and treatment effectiveness research from Brown University.
Duncan first applied this approach in his work with adolescent drug abusers in Houston, Texas in the early 1970s and soon afterward with heroin addicts.
His leadership in this field began at the State University of New York at Brockport, where he collaborated with Robert S. Gold in developing the first course on computers in health education offered at any college.
A few years later, Duncan and Gold, then at Southern Illinois University, taught the nation's first college-level course on PC-based methods in education.
Duncan was a consultant to President Clinton's White House Office of National Drug Control Policy during his tenure as Senior Study Director of the Substance Abuse Research Group of the Westat corporation.
He served as a research associate to the working group on substance abuse treatment for the President's Task Force on National Health Care Reform chaired by First Lady Hillary Clinton in 1993.
He is chair of the Council on Illicit Drugs and a member of the board of directors of the National Association for Public Health Policy.
In 1989 he appealed the conviction for "knowingly receiving visual depictions of minors engaging in sexually explicit conduct, transported and shipped in interstate and foreign commerce, in violation of 18 U.S.C Sec.