An estimated 22.6 million persons aged 12 or older were classified with substance dependence or abuse problems in the United States in 2006, representing 9.2 percent of that age group. Of these, 3.2 million had problems with both alcohol and illicit drugs, 3.8 million had problems with drugs, and 15.6 million were dependent on alcohol. For people who seek treatment, alcohol is by far the most common reason, followed by marijuana, cocaine, pain relievers, heroin, stimulants and hallucinogens. One promising trend is that U.S. government surveys found decreases between 2002 and 2007 in the percentages of youths who used marijuana, Ecstasy, LSD, alcohol, cocaine and cigarettes in their lifetimes, the past year, and the past month. However, illicit inhalant use held steady. The overall cost of substance abuse in the United States—including health- and crime-related costs and losses in productivity—exceeds half a trillion dollars annually, according to the National Institutes of Health. About 120,000 deaths and 40 million serious injuries or illnesses each year are reported as a direct result of substance abuse, according to the National Institute on Drug Abuse.