What is the science of addiction?

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Stages of Addiction

There are three related stages in addiction: acute drug effect, transition to addiction, and end stage addiction. In the early stage, the individual experiences the rewarding effects of the addictive drug. Dopamine is the key brain chemical involved at this stage. At the second stage, the individual transitions from recreational use to addiction. Glutamine is the key brain chemical involved at this stage. At the third and final stage, the individual experiences a strong urge to obtain the addictive drug, loses control of the drug-seeking desire, and experiences a diminished pleasure after using the addictive drug, requiring larger and more frequent dosing to achieve the same initial effects.

Although the science of addiction is still not fully understood, scientists have worked out two major pathways in the brain responsible for addiction. First, there is the mesolimbic pathway mediated by dopamine. Second, the prefrontal cortex, the decision-making center, is responsible for controlling any inappropriate reward responses. Drug addiction can lead to physical changes in these pathways.

Neuro-imaging techniques, such as PET scans and MRIs, have documented changes in the size and shape of nerve cells in the brains of addicts. Networks of nerve cells determine a person’s feelings and behavior. Drugs influence behavior by transforming the way these networks function.

The Dopamine Connection

The biological link among all addictions is dopamine, though some research suggests dopamine plays the central role in some addictions (such as to stimulants) and a minor role in others. This brain chemical is released during pleasurable activities, ranging from sex to eating, to more detrimental behaviors such as drinking and taking drugs. A powerful drug like crack cocaine elevates dopamine levels much faster than normal pleasurable activities. It creates the classic drug-induced feelings of exhilaration and power. In a landmark 1950s experiment, scientists stimulated rodent brains and found that the animals kept returning to the place where they received the stimulation.

Coming down from a drug high is caused by a decrease in dopamine levels. If a person’s brain cells produce excessive dopamine on a regular basis, such as through repeated exposure to an addictive substance, the cells adjust to the unnaturally elevated levels of dopamine in the brain and begin to produce less dopamine. Over time, addicts need drugs just to stimulate dopamine to normal levels. They become trapped in a cycle of cravings and addiction to avoid withdrawal symptoms and depression. It is believed that once a person crosses the line from user to addict, the brain is so changed that he or she can no longer control his or her behavior.

This transformation helps to explain why it is so difficult to break an addiction. Cravings are more significant than physical withdrawal in keeping an addict hooked. Drugs like cocaine and methamphetamine, unlike heroin and alcohol, do not produce intense physical withdrawal symptoms, but they do produce powerful psychological symptoms, including overwhelming cravings. These cravings can be aroused by external or internal stimuli that are as innocuous as walking by a pub or feeling sad.

An Addictive Personality?

Although the influence of dopamine and other elements of brain chemistry on addiction are widely accepted by scientists, not all people react to drugs or addictive behaviors the same way, leading researchers to propose additional factors in the process of addiction. Many addiction professionals believe that addiction stems from a combination of biological, psychological, and environmental factors. Many support groups for addictions recovery also follow this belief. For example, Alcoholics Anonymous describes alcoholism as a physical, emotional, and spiritual disease.

The progression to addiction can develop in this way: A person may have a genetic or biological predisposition to an addiction. If he or she grows up in a family and environment without addiction or stress, he or she may never begin casual drug use. However, if the person grows up in a stressful environment where substance abuse is common and encounters more stressors over time, he or she may begin casual use and, because of the permanent changes in the brain caused by repeated drug use, become a full-blown addict.

Although the science of addiction remains controversial, research into a potential genetic component of addiction is ongoing. Children of alcoholics have been shown to be at a higher risk of becoming alcoholics themselves than the children of nonalcoholics, though it is difficult to determine the exact interplay between biology and environment. Scientists are also studying whether addicts are born with inadequate endorphins, the brain chemicals that regulate stress.


For years, heroin and narcotics addictions have been treated successfully with methadone, which eases withdrawal and blocks the effect of drugs. Naltrexone is another drug commonly used for alcohol and narcotics addiction. Another drug, buprenorphine, is another alternative to methadone in treating narcotics addicts. Useful for detoxification, buprenorphine (usually combined with naltrexone) can also be used for maintenance therapy. Buprenorphine can be prescribed by psychiatrists and other doctors who have received special training. Methadone, in contrast, can only be dispensed from a specially-licensed clinic.

It is unlikely that a magic pill will be found that “cures” addiction. On the other hand, aerobic exercise offers a simple and natural way to help combat addiction. During aerobic exercise, dopamine levels increase in the areas of the brain involved with addiction, and feelings of depression and anxiety decrease.


DiClemente, Carlo C. Addiction and Change: How Addictions Develop and Addicted People Recover. New York: Guilford Press, 2003. Print.

Erickson, Carlton. The Science of Addiction: From Neurobiology to Treatment. New York: W. W. Norton, 2006. Print.

Hart, Carl L., Charles Ksir, and Oakley Ray. Drugs, Society and Human Behavior. 12th ed. Boston: McGraw-Hill-Hill, 2006. Print.

Nutt, David J., et al. "The Dopamine Theory of Addiction: 40 Years of High and Lows." Nature Reviews Neuroscience 16 (2015): 305–312. Print.

Schaler, Jeffrey. Addiction Is a Choice. Peru, Il: Carus Publishing Company, 2000. Print.

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