Meanwhile, illicit drug use among adults 50 to 64 years old has increased in the past decade.
Specifically, illicit drug use among adults 50 to 54 has more than doubled since 2002, reaching 7.2 percent last year. For people 55 to 59, such drug use has more than tripled, reaching 6.6 percent last year.
Marijuana is by far the most-used illicit drug among both children and adults, according to SAMHSA, a division of the Department of Health and Human Services.
At a press conference Wednesday in Washington, officials expressed particular concern about use by those 12 to 17 years old.
“There’s no question that marijuana is harmful to the developing brains of adolescents,” said SAMHSA administrator Pamela Hyde, adding that marijuana use has been linked to “significant I.Q. declines.”