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Drugs, Brains, and Behavior: The Science of Addiction

Drug Abuse and Addiction

What is drug addiction?

Addiction is defined as a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences. It is considered a brain disease because drugs change the brain - they change its structure and how it works. These brain changes can be long lasting, and can lead to the harmful behaviors seen in people who abuse drugs.

Brain and heart metabolism imageSource: From the laboratories of Drs. N. Volkow and H. Schelbert
Addiction is similar to other diseases, such as heart disease. Both disrupt the normal, healthy functioning of the underlying organ, have serious harmful consequences, are preventable, treatable, and if left untreated, can last a lifetime.

Why do people take drugs?

In general, people begin taking drugs for a variety of reasons:

Club image
  • To feel good. Most abused drugs produce intense feelings of pleasure. This initial sensation of euphoria is followed by other effects, which differ with the type of drug used. For example, with stimulants such as cocaine, the "high" is followed by feelings of power, self-confidence, and increased energy. In contrast, the euphoria caused by opiates such as heroin is followed by feelings of relaxation and satisfaction.
  • To feel better. Some people who suffer from social anxiety, stress-related disorders, and depression begin abusing drugs in an attempt to lessen feelings of distress. Stress can play a major role in beginning drug use, continuing drug abuse, or relapse in patients recovering from addiction.
  • To do better. The increasing pressure that some individuals feel to chemically enhance or improve their athletic or cognitive performance can similarly play a role in initial experimentation and continued drug abuse.
  • Curiosity and "because others are doing it." In this respect adolescents are particularly vulnerable because of the strong influence of peer pressure; they are more likely, for example, to engage in "thrilling" and "daring" behaviors.

If taking drugs makes people feel good or better, what's the problem?

At first, people may perceive what seem to be positive effects with drug use. They also may believe that they can control their use; however, drugs can quickly take over their lives. Consider how a social drinker can become intoxicated, put himself behind a wheel and quickly turn a pleasurable activity into a tragedy for him and others. Over time, if drug use continues, pleasurable activities become less pleasurable, and drug abuse becomes necessary for abusers to simply feel "normal." Drug abusers reach a point where they seek and take drugs, despite the tremendous problems caused for themselves and their loved ones. Some individuals may start to feel the need to take higher or more frequent doses, even in the early stages of their drug use.

Examples Of Risk And Protective Factors
Risk Factors Domain Protective Factors
Early Aggressive Behavior Individual Self-Control
Poor Social Skills Individual Positive Relationships
Lack of Parental Supervision Family Parental Monitoring and Support
Substance Abuse Peer Academic Competence
Drug Availability School Anti-Drug Use Policies
Poverty Community Strong Neighborhood Attachment

Is continued drug abuse a voluntary behavior?

The initial decision to take drugs is mostly voluntary. However, when drug abuse takes over, a person's ability to exert self control can become seriously impaired. Brain imaging studies from drug-addicted individuals show physical changes in areas of the brain that are critical to judgment, decisionmaking, learning and memory, and behavior control.7 Scientists believe that these changes alter the way the brain works, and may help explain the compulsive and destructive behaviors of addiction.

No single factor determines whether a person will become addicted to drugs.

Why do some people become addicted to drugs, while others do not?

As with any other disease, vulnerability to addiction differs from person to person. In general, the more risk factors an individual has, the greater the chance that taking drugs will lead to abuse and addiction. "Protective" factors reduce a person's risk of developing addiction.

Risk Factors flow chart

What factors determine if a person will become addicted?

No single factor determines whether a person will become addicted to drugs. The overall risk for addiction is impacted by the biological makeup of the individual - it can even be influenced by gender or ethnicity, his or her developmental stage, and the surrounding social environment (e.g., conditions at home, at school, and in the neighborhood).

Which biological factors increase risk of addiction?

Scientists estimate that genetic factors account for between 40 and 60 percent of a person's vulnerability to addiction, including the effects of environment on gene expression and function. Adolescents and individuals with mental disorders are at greater risk of drug abuse and addiction than the general population.

Children's earliest interactions within the family are crucial to their healthy development and risk for drug abuse.

What environmental factors increase the risk of addiction?

This is a photo of school children
  • Home and Family. The influence of the home environment is usually most important in childhood. Parents or older family members who abuse alcohol or drugs, or who engage in criminal behavior, can increase children's risks of developing their own drug problems.
  • Peer and School. Friends and acquaintances have the greatest influence during adolescence. Drug-abusing peers can sway even those without risk factors to try drugs for the first time. Academic failure or poor social skills can put a child further at risk for drug abuse.

What other factors increase the risk of addiction?

  • Early Use. Although taking drugs at any age can lead to addiction, research shows that the earlier a person begins to use drugs the more likely they are to progress to more serious abuse.8 This may reflect the harmful effect that drugs can have on the developing brain; it also may result from a constellation of early biological and social vulnerability factors, including genetic susceptibility, mental illness, unstable family relationships, and exposure to physical or sexual abuse. Still, the fact remains that early use is a strong indicator of problems ahead, among them, substance abuse and addiction.
  • Method of Administration. Smoking a drug or injecting it into a vein increases its addictive potential.9,10 Both smoked and injected drugs enter the brain within seconds, producing a powerful rush of pleasure. However, this intense "high" can fade within a few minutes, taking the abuser down to lower, more normal levels. It is a starkly felt contrast, and scientists believe that this low feeling drives individuals to repeated drug abuse in an attempt to recapture the high pleasurable state.
Addiction is a developmental disease - it typically begins in childhood or adolescence.

The brain continues to develop into adulthood and undergoes dramatic changes during adolescence.

One of the brain areas still maturing during adolescence is the prefrontal cortex11 - the part of the brain that enables us to assess situations, make sound decisions, and keep our emotions and desires under control. The fact that this critical part of an adolescent's brain is still a work-in-progress puts them at increased risk for poor decisions (such as trying drugs or continued abuse). Also, introducing drugs while the brain is still developing may have profound and long-lasting consequences.

This is a photo of school children

This page was last updated August 2010

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Drugs, Brains, and Behavior - The Science of Addiction

As a result of scientific research, we know that addiction is a disease that affects both brain and behavior.

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