Why Is Alcohol Addictive?
Alcohol addiction is characterized by loss of control over drinking, feeling consumed by thoughts and behaviors around drinking, tolerance to alcohol (needing more for the same effect) and/or withdrawal symptoms, according to the National Institute on Alcohol Abuse and Alcoholism. The causes of alcoholism are social, genetic, psychological and physiological. Alcohol abuse often results in failure to fulfill major obligations at work, school or home; social and legal problems; and/or drinking in hazardous situations.1 In the U.S., the most recent data indicate an estimated 15.1 million people aged 12 and older had an alcohol use disorder (AUD), 65.3 million were past-month binge drinkers, and 16.3 million were heavy alcohol users.2
What Makes Alcohol Addictive?
Ethanol, the primary chemical in alcohol, causes changes in the brain that make people addicted to alcohol. Drinking alcohol temporarily increases production of the feel-good brain chemicals dopamine and serotonin. It also inhibits a brain chemical called glutamate, which produces a feeling of calmness.3 The brain compensates for alcohol’s depressant effects by increasing the activity of excitatory chemicals in an attempt to function normally.4
When you drink alcohol on a regular basis, the brain adapts to the presence of alcohol and greater amounts are required to feel good. This is called tolerance. If a long-term heavy drinker stops drinking suddenly, the brain is forced to readjust, resulting in alcohol withdrawal symptoms. These troubling and potentially life-threatening symptoms often lead to relapse.5
The Role of GABA in Alcohol Addiction
Gamma-aminobutyric acid (GABA) is the brain chemical responsible for alcohol’s sedative and calming effects. Alcohol is a depressant that binds to GABA-A receptors, resulting in increased sedative side effects. The exact mechanism of ethanol actions on GABA-A receptors is unclear. In mouse studies, these receptors appeared to play a role in the rewarding, motor-impairing and sedative effects of ethanol.6 Scientists believe long-term alcohol abuse forces the GABA-A receptor to become less sensitive, which leads to some of the common side effects of alcoholism.
The Science Behind Alcoholism
For decades, researchers have tried to explain the underlying mechanisms responsible for alcohol addiction. Great strides have been made pinpointing the neurochemical changes that take place in the brain.
A Shift in Control Between Different Areas of the Brain
A study published in 2013 found that chronic alcohol exposure shifted behavior control away from the prefrontal cortex, an area of the brain involved in decision-making and control of emotions. When this occurred, responsibility shifted to the dorsal striatum, an area of the brain thought to play a key role in motivation and habit formation. Past studies have shown that people with alcoholism have problems with skills mediated by the prefrontal cortex such as impulse control. Researchers theorize that the shift to increased striatal control over behavior could be a critical step in the progression of alcoholism.7
Greater Sensitivity in the Brain
A study conducted by Wake Forest Baptist Medical Center shed further light on people’s vulnerability to alcohol addiction. “In high doses, alcohol is a depressant, but in low doses, it can have a mellowing effect that results in greater activity. Those low dose effects tend to increase over time and this increase in activity in response to repeated alcohol exposure is called locomotor sensitization,” said co-author Jeff Weiner, PhD.8
The researchers found that mice that were more sensitive drank more alcohol than those without this sensitivity. These mice showed deficits in neuroplasticity, the ability of the brain to adapt its structure based on its experiences. These deficits have been linked to cocaine addiction in other animal studies and have been tied to vulnerability to alcoholism.
Changes in Brain Signaling
A 2018 Swedish study found changes in the brain signaling system contributed to addictive behaviors in rats. Researchers measured the expression of hundreds of genes in five areas of the brain. The largest differences were in the amygdala, an area implicated in emotional reactions. In rats that chose alcohol over sweetened water, one gene was expressed at much lower levels. The gene is the blueprint for the protein GAT-3, a transporter that helps maintain low levels of the inhibitory chemical GABA around the nerve cells. After knocking out GAT-3 in rats that initially chose sweetened water, they reversed their preference and chose alcohol. The researchers also analyzed GAT-3 in brain tissue of deceased humans and found that GAT-3 levels were lower in the amygdala region in people with a documented history of alcohol addiction.9
Alcohol and Endorphins
In 2012, research published in the journal Science Translational Medicineshowed that pleasure associated with drinking alcohol is caused by endorphins being released to areas of the brain called the nucleus accumbens and the orbitofrontal cortex. Endorphins are small proteins with opiate-like effects that are produced naturally in the brain. The nucleus accumbens is a region of the brain that has been linked to addictive behavior, while the orbitofrontal cortex is associated with decision-making. While animal studies conducted over the last 30 years provided clues to the underlying process, this is the first time endorphin release in response to alcohol consumption in these two regions of the brain has been directly observed in humans.10,11
Using PET imaging, researchers at the Ernest Gallo Clinic and Research Center at the University of California, San Francisco (UCSF) studied 25 subjects. Thirteen individuals drank heavily and 12 drank moderately. Regardless of the amount subjects drank, researchers detected endorphins being released in the brain in response to alcohol consumption, although the impact was more pronounced in heavy drinkers. The amount of endorphins being released in the brain’s orbitofrontal cortex was linked to a higher degree of feeling intoxicated. “This indicates that the brains of heavy or problem drinkers are changed in a way that makes them more likely to find alcohol pleasant, and may be a clue to how problem drinking develops in the first place,” said Jennifer Mitchell, PhD, clinical project director at the Gallo Center and an adjunct assistant professor of neurology at UCSF.10,11
How Addictive Is Alcohol?
The following set of criteria can be used to determine how addictive specific drugs are:12
- Withdrawal: Presence and severity of withdrawal symptoms.
- Reinforcement: A measure in human and animal tests of the substance’s ability to cause users to take it repeatedly, and in preference to other substances.
- Tolerance: The amount of a substance needed to satisfy increasing cravings for it, and the level of stable need that is eventually reached.
- Dependence: How difficult it is for a user to quit, the relapse rate, the percentage of people who eventually become addicted, the degree to which the substance is used despite evidence of its harmful effects, and users’ rating assigned to their need for the substance.
- Intoxication: Although it is not typically included as a measure of addiction, intoxication level can be associated with addiction and increases the personal and social damage.11
On a scale of one to six, with one being less serious and six being the most serious, these are the specific addictive properties of alcohol. When compared to other substances, alcohol has a higher withdrawal and intoxication rate than heroin or cocaine.4
- Withdrawal: Six
- Reinforcement: Four
- Tolerance: Four
- Dependence: Three
- Intoxication: Six
People abuse alcohol for a variety of reasons, ranging from social acceptance to pain relief and self-medicating a mental health disorder like depression or anxiety. In addition, research indicates genetic factors make up about half the risk of alcohol addiction. Scientists are hopeful that pinpointing the area of the brain that responds to alcohol will ultimately lead to more effective treatments for alcohol addiction.
1. Substance Abuse – What Drives Alcohol Addiction. Wake Forest Baptist Health website. http://www.wakehealth.edu/Health-Central/What-Drives-Alcohol-Addiction/ Updated November 20, 2015. Accessed July 21, 2018.
2. Reports and Detailed Tables From the 2016 National Survey on Drug Use and Health (NSDUH). Substance Abuse and Mental Health Services Administration website. https://www.samhsa.gov/samhsa-data-outcomes-quality/major-data-collections/reports-detailed-tables-2016-NSDUH Updated May 17, 2018. Accessed July 21, 2018.
3. Feltenstein MW, See RE. Systems Level Neuroplasticity in Drug Addiction. Cold Spring Harb Perspect Med. 2013;3(5):a011916. doi:10.1101/cshperspect.a011916.
4. Alcoholism: A Neurological Perspective. The National High School Journal of Science. http://nhsjs.com/2015/alcoholism-a-neurological-perspective/ Published October 18, 2015. Accessed July 21, 2018.
5. Neuroscience: Pathways to Alcohol Dependence. National Institute on Alcohol Abuse and Alcoholism website.https://pubs.niaaa.nih.gov/publications/AA77/AA77.htm Published April 2009. Accessed July 21, 2018.
6. Kumar S, Porcu P, Werner DF, et al. The role of GABAA receptors in the acute and chronic effects of ethanol: a decade of progress. Psychopharmacology. 2009;205(4):529. doi:10.1007/s00213-009-1562-z.
7. DePoy L, Daut R, Brigman JL, et al. Chronic alcohol produces neuroadaptations to prime dorsal striatal learning. Proc Natl Acad Sci USA. 2013;110(36):14783-14788. doi:10.1073/pnas.1308198110.
8. Wake Forest Baptist Research Provides Clues to Alcohol Addiction Vulnerability. Wake Forest Baptist website.https://www.wakehealth.edu/News-Releases/2013/Wake_Forest_Baptist_Research_Provides_Clues_to_Alcohol_Addiction_Vulnerability.htmUpdated October 21, 2016. Accessed July 21, 2018.
9. Study links molecular changes in the brain to key behaviors in addiction. News Medical website. https://www.news-medical.net/news/20180625/Study-links-molecular-changes-in-the-brain-to-key-behaviors-in-addiction.aspx Published June 25, 2018. Accessed July 21, 2018.
10. Chan AL. Why Alcohol Is So Addictive. Huffington Post. January 13, 2012 http://www.huffingtonpost.com/2012/01/13/alcohol-addictive-endorphins-_n_1202406.html Accessed July 21, 2018.
11. Clue as to why alcohol is addicting: Scientists show that drinking releases brain endorphins. Science Daily website.https://www.sciencedaily.com/releases/2012/01/120111155137.htm Published January 12, 2013. Accessed July 21, 2018.
12. Addictive Properties of Popular Drugs. Drug War Facts website.http://www.drugwarfacts.org/cms/Addictive_Properties#sthash.OLoVqe5J.dpbsAccessed July 21, 2018.