More than 22 million Americans age 12 and older - nearly 9% of the U.S. population - use illegal drugs, according to the government’s 2010 National Survey on Drug Use and Health.

The overall rate of drug use is only slightly higher than the 2009 study but nearly a percentage point above the 2008 survey.

“I am encouraged there were no significant increases in drug use over the past year,” Gil Kerlikowske, the U.S. director of national drug control policy, said in a statement. “However, today’s survey also shows that drug use in America remains at unacceptable levels.”

Marijuana, cocaine, heroin, hallucinogens, inhalants and some prescription drugs used for non-medical purposes were counted in the survey. Marijuana was the most commonly used drug, with more than 17 million users in 2010, 3 million more than in the 2007 survey.

In 2010, 7 million people used psychotherapeutic drugs (including stimulants, tranquilizers, painkillers and sedatives) for non-medical purposes, and 1.2 million people used hallucinogens, according to the study. The numbers are similar to the past few years.

One and a half million people used cocaine, similar to recent years' study results but a drop of nearly 1 million from 2006. Methamphetamine use dropped by more than half between 2006 and 2010, to only a 10th of 1% of the population, according to the survey.

The number of young people using drugs has continued to increase. In 2008, 19.6% of 18- to 25-year-olds used drugs, but in 2010’s survey, that number had climbed to 21.5%. The increase is largely due to marijuana use, according to the study.

Drug use among 12- to 17-year-olds stayed steady in the survey, at about 10%.

States allowing medical marijuana could be fueling the increases in drug use, Kerlikowske said.

“Emerging research reveals potential links between state laws permitting access to smoked medical marijuana and higher rates of marijuana use,” his statement said. “I urge every family - but particularly those in states targeted by pro-drug political campaigns - to redouble their efforts to shield young people from serious harm by educating them about the real health and safety consequences caused by illegal drug use.”

Marijuana is the most common drug for first-time users, according to the study. Among people who started using drugs in the year before the survey, 62% said they first used marijuana, 26% first used prescription drugs like tranquilizers and stimulants, and 9% first used inhalants.

The age when people start using marijuana is going up. The study found that in 2010, the average age of a first-time marijuana user was 18.4 years. In the 2002 study, it was 17 years old.

Nearly half of youths between 12 and 17 years old said it would be "fairly easy" or "very easy" to get marijuana, one in five said it would be easy to get cocaine, and one in 10 said it would be easy to get heroin, according to the study.

Alcohol use

About 131 million people 12 and older in the United States drink alcohol, according to the 2010 survey. That’s roughly half the population and similar to the year prior. Nearly a quarter of the population age 12 and older participated in what the study calls binge drinking, or having five or more drinks in the same occasion, at least once in the past month. Nearly 7% of the population reported binge drinking on five days in the month before the survey.

Ten million 12- to 20-year-olds drink, according to the survey, and 65% of those binge drink. These numbers represent a drop of about 2 percentage points each from the 2002 survey.

More than 11% of the population drove under the influence of alcohol in the year before the study. The number is a drop of about 3 percentage points from the 2002 study.

The most likely age group to drive after drinking was 21- to 25-year-olds, according to the study.



Tobacco use

Nearly 70 million Americans age 12 and over use tobacco, according to the study, more than a quarter of the population in that age group. The numbers represent a drop of about 3 percentage points from the 2002 survey. In both studies, cigarette smoking made up the majority of the tobacco use, followed by cigars and smokeless tobacco. However, only cigarette use significantly declined during those years.

The use of tobacco by younger people has declined. The 2002 study showed that about 15% of people age 12 to 17 used tobacco, while the 2010 numbers were closer to 11%.

Nearly 59% of new smokers in the 2010 survey were under 18 when they first started smoking.

Treatment

More than 23 million Americans age 12 and older needed some sort of treatment for drug or alcohol use problems, according to the 2010 study. But only 2.6 million people got that treatment. Of the people who didn’t get treatment, most indicated in the survey that they did not feel they need it.