[YT video="w0NCRDa6QH0" title="ABC News Talks With Promises' Dr. Greg Skipper About 'Functioning' Heroin Addicts"] ABC's "World News with Diane Sawyer\u201d recently spoke with Promises Treatment Centers' director of Professionals Health Services Dr. Greg Skipper about the growing use of heroin in the U.S. Nearly 670,000 Americans use heroin, according to a report by the Substance Abuse and Mental Health Services Administration, double the rate just five years ago. In describing the effect heroin has on users, Dr. Skipper, a fellow of the American Board of Addiction Medicine, told the network that "there's a tendency" of just "going to sleep in the middle of a sentence." He said there are many "functioning heroin addicts" in treatment. "We see it all the time." The subject hit close to home for reporter Cecilia Vega, who spoke of her father's addiction to the drug and his untimely death.