Addiction is a Brain Disease
What is the Evidence?

Background

Until recently, there was little solid scientific evidence to explain why some people lose control over their use of alcohol or other drugs. Without such evidence, the public, and even some scientists and physicians, have been free to argue that alcoholism and other drug addictions are something other than diseases. An understandable result is that policy makers and image makers in our society fail to understand the nature of addiction, and often blame persons with addiction for their “irresponsibility”. Even though the American Medical Association declared alcoholism (alcohol addiction) a disease in 1967, acceptance of these views is not universal. Too often addiction is addressed only by the criminal justice system, not a disease state that must be addressed by the health care system.

Terminology

Not only is there scientific evidence that some drug users have a disease, many scientists now affirm that addiction is a chronic brain disease that can be treated successfully; in fact as successfully as many other chronic diseases like asthma, hypertension, and diabetes. This bold statement is fully substantiated by neuroscience (science of the brain and how it works), genetic, and clinical studies. “Addiction is a brain disease” is now the mantra of the National Institute on Drug Abuse.

So what is the science behind this story? To begin to understand the science, a person needs to realize that not all drug overuse is “addiction”. The American Psychiatric Association and World Health Organization now provide diagnostic criteria to differentiate those drug users who have control over their drug use (i.e., those who do not have a disease) and those who don’t have such control consistently (i.e., those who have a disease). The former group can be diagnosed as having “substance abuse” (by criteria found in the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition - DSM-IV, and in the International Classification of Diseases, ICD-10); the latter group can be diagnosed as having “substance dependence,” by other criteria appearing in the same two diagnostic manuals. The term “substance (chemical) dependence” is essentially interchangeable with the term “addiction.” Thus, we are able to talk about what causes “dependence” (the brain disease) versus what causes “abuse” of drugs. Both conditions produce serious consequences, but they are different in their causes and the way they can be overcome. Generally, drug “abuse” declines through educational approaches, counseling, coercion, incarceration, or restriction of drug availability. To overcome the disease of “chemical dependence” or “addiction” requires other measures.

The Evidence

Geneticists and neuroscientists have studied substance dependence for several decades. It is now accepted that the primary site of this disease is the brain’s reward system (also known as the mesolimbic dopamine system) and closely connected centers in the brain, especially centers in the orbitofrontal cortex where judgment, “executive functioning” and impulse control capacities reside.

Epidemiologic studies indicate that the likelihood of developing substance dependence varies widely depending on the drug one may use. The following list describes “lifetime prevalence risk of dependence”: nicotine - 32%, heroin - 23%, cocaine - 17%, alcohol - 15%, cannabis - 9%, “sedatives” (e.g., benzodiazepine anti-anxiety medications) - 9%, amphetamines - 11%, opioid analgesics - 9%, psychedelics (such as LSD) - 5%, and inhalants - 4%, suggesting that regular use does not guarantee dependence and that each drug has a different potential to cause dependence. Even if further research causes these numbers to change somewhat, it is still clear that each of these drugs/drug classes has a different potential to result in a case of addiction. One probable explanation is that various drugs are associated with the malfunctioning (termed: dysregulation) of various specific neurotransmitter systems in the reward pathway.

If, for example, a drug is taken over a long period of time, a neurotransmitter system affected by that drug will change slowly (i.e., it will “neuroadapt”) until it reaches a point where a threshold is reached, and then the drug user begins to have trouble controlling the use of the drug. The rate of neuroadaptation could occur quickly or it might take years, depending on the genetic vulnerability of the individual, plus other factors. The manner in which drugs match up with specific neurotransmitter systems in the reward pathway helps us understand why people with addiction have “drugs of choice.”

The Promise of Treatment and Twelve Step Programs

Knowing that something is a disease and is not self-imposed as a result of simply being “weak-willed” helps to reduce social stigma, thereby leading to more research and improved treatment outcomes, as has occurred with diseases such as cancer, schizophrenia, and diabetes. Knowing that a disease can be arrested through treatment can further reduce stigma against the disease. Since substance dependence is a brain disease, and people get better with treatment, then something obviously changes in the brain - specifically in the dysregulated neurotransmitter systems of the reward pathway - when people improve. It is known that clinical interventions and professional treatment help substance dependent people get better - in some cases they enjoy sustained recovery over many years. The “treatments” include intensive individual, family, and group counseling; resolution of ongoing psychiatric, neurological, and medical issues; and long-term follow-up including “chronic disease management” and “case management.” Medications are available to help patients who experience frequent relapse (unintentional “falling off the wagon”) episodes. Introduction to twelve-step support groups that enhance and maintain sobriety is very effective in such individuals.

What do professional counseling, medications, and mutual-help activities (such as Alcoholics Anonymous) that reduce relapse have in common? In substance dependent patients who get better, these disparate interventions probably change brain reward function in the direction of “normalcy,” improving the functioning of the orbitofrontal cortex and reward pathway and the ability to resist urges to use, as well as reducing the power of environmental cues that trigger renewed drug use. Some scientists speculate that the dysregulation of brain regions connected with the reward system can never be fully reversed, but only “pushed back” toward normal much like an antidepressant changes brain chemistry toward normal in a depressed patient. Continuity of many approaches to treatment can maintain improvements in functioning, giving the person a better chance of living a happy, joyous, and drug-free life. Healing interventions can also include attendance at 12-step meetings on a regular basis. For some people, the spirituality they develop through AA might be the best way of maintaining the normalizing changes in the functioning of their brains!

Brain imaging studies accumulating in this century clearly show that counseling methods such as cognitive behavioral therapy can change brain function in anxious or fearful patients. These and other studies are bridging the gap between psychology and neuroscience, and helping scientists understand the magical workings of the brain when diseased and when in recovery.

The prognosis for long-term stable recovery can be expected to vary from person to person based upon the severity of the disease, a person’s psychological resilience, and the quality and consistency of treatment. But as attested to by the millions in recovery, this brain disease can be arrested and overcome! Recovery is real and is enjoyed by people with addiction, every day.

Adapted from an upcoming publication of the National Council on Alcoholism and Drug Dependence, Inc. (NCADD), New York, NY.
More detail on this subject can be found in “Science of Addiction: From Neurobiology to Treatment” by C.K. Erickson (W.W. Norton, New York, NY, 2007), a book written for counselors and the general public.