Endorphins are naturally occurring opiates that are found in tiny amounts in specific parts of the brain. They play a role in pain modulation as well as in the regulation of mood states. Alcohol’s addictive properties appear to involve a mechanism most simply described as the brain getting hooked on its own opiates. This explains why alcoholics and their relatives have an exaggerated secretion of endorphins which can be measured in the bloodstream, and why an opiate-blocking drug such as naltrexone is an effective aid for treating alcoholism in some people. If you have a family history of alcoholism, your body may actually react to alcohol as strongly as it would to a drug like morphine.

This abnormal reaction has been studied statistically through measurement of the circulating blood levels of a compound known as β-endorphin. After a person is exposed to alcohol, levels of β-endorphin tend to rise in those with a family history of alcoholism but not in those with no such history. (This effect is seen when large groups are analyzed, but cannot as yet be used to diagnose the risk of alcoholism in an individual.)

A great deal of research is being done on the effectiveness of opiate-blocking drugs like naltrexone (Revia, Trexan) in the treatment of alcoholism. These drugs blunt the activity of opiate receptors in the brain. In other words, they prevent the brain from producing a euphoric response to opiates. In alcoholics, naltrexone has been shown to increase periods of abstinence and decrease the severity of relapses.

Another chemical thought to be important in the brain’s response to addictive substances is dopamine. Dopamine is one of numerous chemicals that communicate messages between nerve cells. Most of the nerve cells in the pleasure center of the brain are activated when there is increased brain activity of dopamine. Researchers are examining the chemical receptors that allow nerve cells to respond to dopamine. It appears that some people from alcoholic families tend to have defects in these receptors.

This may mean that for the people with a genetic risk of alcoholism the pleasure center doesn’t work just right. The experience of being intoxicated provides a sense of well-being that might otherwise be absent. The brain quickly learns that it can feel “normal” when the substance is present, and so there is strong motivation for an individual to use alcohol again and again. Fortunately, the majority of people who get sober and stay in recovery do not give up a sense of well-being. In fact, many recovering people say that although they felt good drinking or doing drugs at first, they have never felt better psychologically than they do in recovery.

Mechanisms causing a unique response to an addictive drug are probably also in play with marijuana, cocaine, heroin, and other drugs. The risk of becoming addicted to one of these drugs is higher for those with others in the family who are addicted than it is in the general population.

Elizabeth Connell Henderson, M.D.

Glossary

Appendix A: Regulation of Addictive Substances

Appendix B: Sources of Additional Information