In 2002, drug use by American teenagers declined in a broad range of categories, including the use of MDMA (ecstasy), marijuana, and cigarettes. Studies of marijuana smokers during inpatient treatment suggest that marijuana dependence, like dependence on other addictive drugs, is associated with withdrawal symptoms, such as irritability, anger, depressed mood, headaches, restlessness, lack of appetite, and craving, that make it difficult to stop using the drug. Marijuana smokers treated with an experimental compound reported reduced highs and had smaller heart rate increases than untreated smokers. The marijuana of today is far more potent than the marijuana of 30 years ago. Two brief family-focused drug abuse prevention programs have produced long-term reductions in substance abuse among adolescents in rural Iowa public schools that were assigned to the programs in the sixth grade. Chronic marijuana abuse can restrict blood flow to the brain and increase the risk of stroke for young men aged 18 to 30. Memory and learning problems caused by heavy marijuana smoking persist for at least a week after cessation of use of the drug, but they appear to resolve completely within a month. In the first large-scale study designed to evaluate drug abuse treatment outcomes among adolescents in age-specific treatment programs, researchers have found that longer stays in these treatment programs can effectively decrease drug and alcohol use and criminal activity as well as improve school performance and psychological adjustment. Television public service announcements decrease marijuana use in targeted teens. Males are more likely than females to abuse drugs. Research suggests that in the brain, compounds called endocannabinoids inhibit pain perception and help to regulate movement. Researchers are beginning to clarify the role that genes play in predisposing individuals to drug abuse. Cultural influences and ethnic identification may significantly influence drug use among Puerto Ricans, African-Americans, and Asians. A new science education campaign has been launched to provide middle school students with information abut how drugs work in the brain.