The Science of Addiction

First published 2006. To view the latest Heads Up content, click here.

risktable.JPGHow serious is drug addiction?
According to the National Institute on Drug Abuse (NIDA),drug addiction is “a chronic, relapsing disease, characterized by compulsive drug seeking and use, and by neurochemical and molecular changes in the brain.” Like other chronic diseases, drug addiction can seriously impair the functioning of the body’s organs. It can also increase the risk of contracting other diseases, such as HIV and viral hepatitis, not just among those who inject drugs, but also through risky behaviors stemming from drug-impaired judgment.

Drug addiction often results from drug abuse, which is the use of illegal drugs or the inappropriate use of legal drugs to produce pleasure, to alleviate stress, or to alter or avoid reality (or all three). Risk factors for addiction and protective factors against it (see table) can be environmental as well as genetic. Scientists estimate that genetic factors, including environmental effects on these genes, account for between 40 and 60 percent of a person’s vulnerability to addiction. Recent research has begun to uncover which genes make a person more vulnerable, which genes protect a person against addiction, and how one’s genes and environment interact. There is also evidence that individuals with mental disorders have a much greater risk of drug abuse and addiction than the general population. 

Learn more about the role of genes in drug addiction.


The impact of addiction can be far-reaching:

  • Cardiovascular disease
  • Stroke
  • Cancer
  • Hepatitis C
  • Lung disease
  • Obesity
  • Mental disorders

What Is Addiction? 

  • Addiction is a complex disease. No single factor can predict who will become addicted to drugs. Addiction is influenced by a tangle of factors involving one’s genes, environment, and age of first use.
  • brainchart.JPGAddiction is a developmental disease. It usually begins in adolescence, even childhood, when the brain is continuing to undergo changes. The prefrontal cortex—located just behind the forehead—governs judgment and decision-making functions and is the last part of the brain to develop. This fact may help explain why teens are prone to risk-taking, and why they are also particularly vulnerable to drug abuse. It also explains why exposure to drugs during the teen years may affect the likelihood of someone becoming an addict in the future. 
  • Prevention and early intervention work best in the teen years. Because the teen brain is still developing, it may be more receptive to interventions to alter the course of addiction. Research has shown many risk factors that lead to drug abuse and addiction: mental illness, physical or sexual abuse, aggressive behavior, academic problems, poor social skills, and poor parent-child relations. This knowledge, combined with better understanding of how the teen brain works, can be applied to prevent drug abuse from starting or to intervene early to stop it when warning signs emerge.


Vicodin and OxyContin: Legal but Dangerous

Addiction can occur with many drugs, not just “street drugs” like heroin. Painkilling drugs such as Vicodin and OxyContin may seem safe because they’re available by prescription, but many teens don’t realize that they are also very addictive if not used as directed by a physician. This is not surprising, since the active ingredient in OxyContin acts at the same site in the brain as heroin.

The case of Jacob [name changed] puts the dangers of prescription painkillers in focus. Jacob began using OxyContin at 18, and before long was selling pills to help support his habit. (Selling prescription drugs makes you a drug dealer and subject to criminal prosecution.) Eventually Jacob moved from OxyContin to heroin. “If I’d never touched OxyContin, I wouldn’t have done heroin,” he claims. Luckily, Jacob eventually faced his addiction and entered a drug treatment program.


Learn more about the science of opioid addiction.


Latest Research: The Science of “Dread”

New research shows that people who substantially dread an adverse experience have a different biology than those who better tolerate the experience.

Dr. Gregory Berns of Emory University School of Medicine and his colleagues used MRI imaging to observe brain activity patterns in non-drug abusers who were awaiting brief electrical shocks (the adverse experience).

The subjects were given the option of a larger shock to occur in a shorter period of time, or a smaller shock after a longer period of time. The scientists noted two groups: “extreme dreaders,” who could not tolerate a delay and preferred an immediate (and stronger) painful stimulus; and “mild dreaders,” who could tolerate a delay for a milder shock. The findings suggest that dread derives, in part, from attention—and is not simply a fear or anxietyreaction.

Continuing to use drugs despite expecting a bad outcome is a hallmark of addiction. The results of this study form the foundation for future research to determine whether drug abusers exhibit disruption in the brain systems that process “dread”—the anticipation of unpleasant consequences.

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