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NIDA InfoFacts

Understanding Drug Abuse and Addiction

June 2008


Drug abuse and addiction are a major burden to society. Estimates of the total overall costs of substance abuse in the United States -- including health- and crime-related costs as well as losses in productivity -- exceed half a trillion dollars annually. This includes approximately $181 billion for illicit drugs,1 $168 billion for tobacco,2 and $185 billion for alcohol.3 Staggering as these numbers are, however, they do not fully describe the breadth of deleterious public health -- and safety -- implications, which include family disintegration, loss of employment, failure in school, domestic violence, child abuse, and other crimes.

What Is Drug Addiction?




What Happens to Your Brain When You Take Drugs?




Nearly all drugs, directly or indirectly, target the brain's reward system by flooding the circuit with dopamine. Dopamine is a neurotransmitter present in regions of the brain that control movement, emotion, motivation, and feelings of pleasure. The overstimulation of this system, which normally responds to natural behaviors that are linked to survival (eating, spending time with loved ones, etc.), produces euphoric effects in response to the drugs. This reaction sets in motion a pattern that "teaches" people to repeat the behavior of abusing drugs.

As a person continues to abuse drugs, the brain adapts to the overwhelming surges in dopamine by producing less dopamine or by reducing the number of dopamine receptors in the reward circuit. As a result, dopamine's impact on the reward circuit is lessened, reducing the abuser's ability to enjoy the drugs and the things that previously brought pleasure. This decrease compels those addicted to drugs to keep abusing drugs in order to attempt to bring their dopamine function back to normal. And, they may now require larger amounts of the drug than they first did to achieve the dopamine high -- an effect known as tolerance.

Long-term abuse causes changes in other brain chemical systems and circuits as well. Glutamate is a neurotransmitter that influences the reward circuit and the ability to learn. When the optimal concentration of glutamate is altered by drug abuse, the brain attempts to compensate, which can impair cognitive function. Drugs of abuse facilitate nonconscious (conditioned) learning, which leads the user to experience uncontrollable cravings when they see a place or person they associate with the drug experience, even when the drug itself is not available. Brain imaging studies of drug-addicted individuals show changes in areas of the brain that are critical to judgment, decisionmaking, learning and memory, and behavior control. Together, these changes can drive an abuser to seek out and take drugs compulsively despite adverse consequences -- in other words, to become addicted to drugs.

Why Do Some People Become Addicted, While Others Do Not?


  • Biology. The genes that people are born with -- in combination with environmental influences -- account for about half of their addiction vulnerability. Additionally, gender, ethnicity, and the presence of other mental disorders may influence risk for drug abuse and addiction.
  • Environment. A person's environment includes many different influences -- from family and friends to socioeconomic status and quality of life in general. Factors such as peer pressure, physical and sexual abuse, stress, and parental involvement can greatly influence the course of drug abuse and addiction in a person's life.
  • Development. Genetic and environmental factors interact with critical developmental stages in a person's life to affect addiction vulnerability, and adolescents experience a double challenge. Although taking drugs at any age can lead to addiction, the earlier that drug use begins, the more likely it is to progress to more serious abuse. And because adolescents' brains are still developing in the areas that govern decisionmaking, judgment, and self-control, they are especially prone to risk-taking behaviors, including trying drugs of abuse.

Prevention Is the Key

Drug addiction is a preventable disease. Results from NIDA-funded research have shown that prevention programs that involve families, schools, communities, and the media are effective in reducing drug abuse. Although many events and cultural factors affect drug abuse trends, when youths perceive drug abuse as harmful, they reduce their drug taking. It is necessary, therefore, to help youth and the general public to understand the risks of drug abuse, and for teachers, parents, and healthcare professionals to keep sending the message that drug addiction can be prevented if a person never abuses drugs.

For more information on understanding drug abuse and addiction, please see our booklet, Drugs, Brains, and Behavior -- The Science of Addiction, at

For more information on prevention, please visit

For more information on treatment, please visit

To find a publicly-funded treatment center in your state, please call 1-800-662-HELP or visit


  1. Office of National Drug Control Policy. The Economic Costs of Drug Abuse in the United States: 1992-2002. Washington, DC: Executive Office of the President (Publication No. 207303), 2004.
  2. Centers for Disease Control and Prevention. Annual Smoking-Attributable Mortality, Years of Potential Life Lost, and Productivity Losses -- United States, 1997-2001. Morbidity and Mortality Weekly Report 54(25):625-628, July 1, 2005.
  3. Harwood, H. Updating Estimates of the Economic Costs of Alcohol Abuse in the United States: Estimates, Update Methods, and Data Report. Prepared by the Lewin Group for the National Institute on Alcohol Abuse and Alcoholism, 2000.

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This article was provided by U.S. National Institute on Drug Abuse.
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