Pamela S. Hyde of the Substance Abuse and Mental Health Services Administration said the increases may require the doubling of substance abuse treatment services needed for this population by 2020.
The report, "Illicit Drug Use among Older Adults," shows that an estimated 4.3 million adults aged 50 or older, or 4.7 percent, used an illicit drug in the past year.
Less than 9 percent of men ages 50-54 had used marijuana in the past year, while 3.9 percent of women in this age group did, the report said.
Although marijuana use was more common than non-medical use of prescription drugs for adults age 50-59, among those ages 65 and older, non-medical use of prescription drugs was more common than marijuana.
The report is based on data collected (2006-08) from a nationally representative sample of 19,921 adults age 50 and older who participated in the Substance Abuse and Mental Health Services Administration's National Survey on Drug Use and Health.