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What is Drug Addiction?

Learn how drug addiction can alter and damage brain function...

drug addiction

Researchers and scientists call drug addiction a "brain disease," primarily because drugs change the brain, its chemistry, and how it functions - or fails to function.

Putting the words "addiction" and "disease" in the same sentence hasn't always been the norm. For most of the 20th century, most people, including doctors and other health care professionals, considered addiction to be a moral weakness, a personal failing - a sign of unsound character.

Over the last few decades, scientific advances made in brain physiology and functioning have dispelled these beliefs. Additionally, technological advances in non-invasive brain imaging techniques show, unequivocally, the physical manifestations and obstructive nature of the disease.

Those addicted to drugs start out as drug abusers, sampling and experimenting with drugs. Over time, for some sooner rather than later, their bodies become dependent on the drugs, functioning abnormally because of profound changes in the brain's cells and intricate circuitry. Using a simplistic analogy, the effect of drugs on brain cells mimics malfunctioning smoke detectors, detectors randomly going off without any signs of smoke or fire.

Unlike smoke detectors, however, addicts don't have any easy way to "turn off" malfunctioning brain circuitry. Addictions are complicated, and require long-term rehabilitation to manage. But the good news is that professionals now treat addiction as a serious medical condition, helping individuals manage its effects, and recover from its harmful ramifications.

The addictive brain

The brain is a 3-pound control center for emotions, feelings, thoughts, cognition, behaviors, and movements. One of the main components of that control center, a brain neurotransmitter called dopamine, plays a major role in motivation, pleasure, and learning. Researchers now understand how drugs alter dopamine levels, interfering with the way nerve cells typically send, receive, and process information.

meth and the brain

Healthy brains naturally produce neurotransmitters to facilitate communication between the brains' nerve cells, called neurons. Dopamine is a chemical that informs us of what's good, or pleasurable, such as steak cooking on an outside grill. If you're hungry and you smell the steak, certain neurons start kicking out dopamine, sending the chemical substance to other neurons that have dopamine receptors. Some of the dopamine, however, doesn't get picked up by these receptors, and the original neurons must take back, or reuptake, the excess dopamine.

When individuals use illicit drugs, the brain's finely-tuned neurotransmission process starts to work differently - abnormally. Drugs such as cocaine cause neurons to pump out dopamine in skyrocketing amounts, amounts larger than the neurons can handle, disrupting the normal processing and recycling of dopamine. These drugs can pump out 2 to 10 times the natural amount of dopamine, and the "pleasurable" sensations last much longer than natural levels of dopamine. Communication messages sent from the neurons are out of proportion, disrupting other bodily systems.

Other drugs, such as marijuana and heroin simulate the chemical structure of neurotransmitters, "tricking" neuron receptors into receiving them, and activating nerve cells. Even though the chemicals from these drugs look like naturally occurring neurotransmitters, they produce much different effects - again sending out abnormal messages to other parts of the brain and body. Long-term use of these drugs dramatically alters neurons, brain circuits, and the overall health of the brain.

Drug Tolerance

One of the most pernicious affects of drugs on the brain is the development of tolerance. The constant surges in abnormally high levels of dopamine (other neurotransmitters are also increased) cause the brain to produce less naturally occurring dopamine. When these low levels of natural dopamine are released, the brain no longer responds as it did before, and the ability to experience pleasure "naturally" disappears. This leaves many addicts lifeless, depressed, and feeling "low."

Previous activities that produced natural "highs," such as listening to music, art making, hiking, going to movies, or enjoying the company of friends and family, no longer trigger normal, pleasurable feelings. To "lift" their spirits, addicts must now take drugs to simply try and get their dopamine levels to normal levels. To reach a state of euphoria, similar to their first usage of drugs, they must continually take larger and larger amounts of the drug.


The pleasure and reward system instigated by dopamine is one of the body's main survival mechanisms. The brain's intricate circuitry functions in such a way as to keep telling our bodies what is needed to sustain life - such as eating, or having sex. In this way, dopamine levels trigger our bodies in such a way to refocus our attention to things that are not only pleasurable, but things we need as well.

When addicts deluge their brain's circuitry with drugs, it retrains the brain to focus exclusively on the drugs, tricking addicts to think that they need the drugs to survive. Addicts' brains mistakenly think that drugs are required just as satisfying other bodily needs are required.

Intense, sometimes uncontrollable drug cravings, are one of the signature hallmarks of drug addiction. Addicts often go through extremely unpleasant withdrawal or detoxification when drugs are withheld, hard to find, or they simply decide to stop using and begin a substance abuse treatment program. Many need additional medication to help control these cravings.

Possible causes of addiction

Researchers are still trying to understand why some individuals can use, even abuse, drugs and not become addicted, while others become addicted on initial usage. (For an explanation on abuse, dependency and addiction, see What is Substance Abuse and Addiction?)

While an exact reason for addiction still eludes researchers, their emphasis on studying healthy and unhealthy levels of dopamine, and how the brain responds to it, has provided new insights and breakthroughs. For example, brain researchers now know that some individuals are born with lower amounts of dopamine receptors than others. This could mean drugs that increase levels of dopamine, or dopamine-like substances, cause some individuals to more easily become addicted.

Other researchers focus on socioeconomic factors, or underlying mental illnesses, as leading to or contributing to the disease. Poverty and extreme stress are linked to drug addiction. And the high rate of mental disorders, such as depression, anxiety (see Anxiety), and bipolar disorder (see Bipolar Disorder), that often accompany addiction strongly suggest a possible correlation to the disease.

Often, it's the complex combination of many physical, emotional, and psychological factors that cause many individuals to become addicted. Fortunately, substance abuse counselors and other professionals working at substance abuse treatment centers are able to help these individuals recover from addiction. (For more information on substance abuse treatment centers, see Substance Abuse Treatment Centers.)

If you have a desire to help others with addiction diseases, you should consider a career in substance abuse and behavioral disorders. Many schools offer psychology degrees with specializations in this field, leading to careers as substance abuse counselors. For more information on these degrees, request information from the schools offering psychology or counseling degree programs.

Counseling Schools & Colleges

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