Addiction is a condition characterized by repeated, compulsive seeking and use of drugs, alcohol or other similar substances despite adverse social, mental and physical consequences. It is usually accompanied by psychological and physical dependence on the abused substance and the appearance of withdrawal symptoms when the addictive substance is rapidly decreased or terminated. When addiction exists, the drug use controls the individual rather than the individual controlling the usage. When a person loses the ability to make a rational choice about whether or not to use a drug or alcohol, he or she is addicted.
If the drug fulfills a valuable need, you may find yourself increasingly relying on it. You may take drugs to calm or energize yourself, or make you more confident. You may start using prescription drugs to cope with panic attacks or relieve chronic pain. Until you find alternative, healthier methods for overcoming these problems, your drug use will likely continue. If you are using drugs to fill a void in your life, you’re more at risk of crossing the line from casual use to drug abuse and addiction. To maintain a healthy balance in your life, you need to have positive experiences and feel good about your life without any drug use.
The initiation of drug and alcohol use is most likely to occur during adolescence, and some experimentation with substances by older adolescents is common. For example, results from 2010 Monitoring the Future survey, a nationwide study on rates of substance use in the United States, show that % of 12th graders report having used an illicit drug at some point in their lives.  In the 30 days prior to the survey, % of 12th graders had consumed alcohol and % of 12th graders had smoked tobacco cigarettes .  In 2009 in the United States about 21% of high school students have taken prescription drugs without a prescription.  And earlier in 2002, the World Health Organization estimated that around 140 million people were alcohol dependent and another 400 million with alcohol-related problems.