National Survey on Drug Use and Health (NSDUH)
According to the 2007 NSDUH, an estimated 6.9 million persons, or 2.8 percent of the population, aged 12 or older had used prescription psychotherapeutic medications nonmedically in the month prior to being surveyed. This includes 5.2 million using pain relievers (an increase from 4.7 million in 2005), 1.8 million using tranquilizers, 1.1 million using stimulants, and 350,000 using sedatives.
Past-month nonmedical use of prescription-type drugs among young adults aged 18 to 25 increased from 5.5 percent in 2002 to 6 percent in 2007. This was primarily due to an increase in pain reliever use, which was 4.1 percent in 2002 and 4.6 percent in 2007. However, nonmedical use of tranquilizers remained the same over the 6-year period.
Among persons aged 12 or older who used pain relievers nonmedically in the past 12 months, 56.5 percent reported that they got the drug most recently used from someone they knew and that they did not pay for it. Another 18.1 percent reported that they obtained the drug from one doctor. Only 4.1 percent purchased the pain reliever from a drug dealer or other stranger, and just 0.5 percent reported buying the drug on the Internet. Among those who reported getting the pain reliever from a friend or relative for free, 81 percent reported in a follow-up question that the friend or relative had obtained the drug from one doctor only.
(Retrieved on October 25, 2010 from National Institute on Drug Abuse's website)