Addiction is a devastating disease both for addicts and their loved ones. And unfortunately, it's not uncommon: 23.5 million people in the U.S. (9.3 percent) needed treatment for a drug or alcohol abuse problem in 2009.

Addiction doesn't just refer to substance abuse: Pathological gambling, which is often regarded as a behavioral addiction that has many similarities with substance abuse disorders, affects between .5 and 1 percent of the population.

How Addiction Develops

Addiction—whether to cigarettes, alcohol, drugs, or gambling—doesn’t just happen overnight. "A person isn’t born with an addiction," says Mark Willenbring, MD, DLFAPA, of the Alltyr Clinic in Saint Paul, Minnesota.

So how does it start? "There may be an underlying vulnerability to addiction that causes someone to start using," says Frances Levin, MD, chief of the Division of Substance Abuse and Kennedy Leavy Professor of Psychiatry at the Columbia University Medical Center and Columbia University/New York State Psychiatric Institute's Department of Psychiatry. So "If a vulnerable individual takes an opioid for pain, they may become addicted where another person would not."

Certain risk factors may predispose people to addiction:

  • Genes: "About 60 percent of alcohol and drug dependence is attributable to a person's genetic makeup," says Willenbring. For instance, people who have a first-degree relative, such as a parent or sibling, with a substance abuse problem are at an increased risk for becoming addicted themselves. "But other factors must be present," he adds.
  • Environment: Stress, peer pressure, and regular exposure to people (especially family members) engaged in addictive behaviors increase addiction risk.
  • Development: The earlier one begins to use drugs or alcohol, the more likely he will become addicted.

Certain individual traits can also set a person up to become addicted, Willenbring says:

  • Behavioral Disinhibition: An addict tends to have a "behavioral disinhibition," meaning that he has a weaker than normal ability to control his behavior and set limits on the consumption of a particular substance.
  • Vulnerability to the Substance: Addicts also must have a vulnerability to a particular substance. For instance, while many people feel sedated when taking opioids for pain after having a wisdom tooth extracted, an addict might feel wonderful and stimulated.
  • Easy and Rapid Tolerance: "I call it the 'hollow leg syndrome,'" Willenbring says. "When others who drink a great deal will be passing out, the addict can drink just as much and not even suffer a hangover."

The more risk factors a person has, the likelier it is that he or she will become addicted.


Just like a drug, a behavior can become addictive. "PG (pathological gambling) and substance dependence share specific diagnostic features, including those of tolerance and withdrawal," write the authors of an article in the American Journal of Drug and Alcohol Abuse. "Tolerance in substance dependence describes the use of increasing amounts of a substance in order to achieve an equivalent desired effect of previous consumptions.... In PG, tolerance is operationalized as gambling with increasing amounts of money in order to achieve the desired subjective effect, eg. excitement, or that the same level of gambling leads to a diminished subjective response."

Pathological gambling addicts can experience anxiety or irritability when they cut down or quit gambling, note the authors.

Changes in the Brain

An addiction to drugs causes the brain to change. That's because drugs contain certain chemicals that disrupt the way that nerve cells send, receive, and process information, either by imitating the brain’s natural chemical messengers (like heroin and marijuana), or overstimulating the brain's "reward circuit" (cocaine and methamphetamine). When the reward system gets overstimulated, euphoric effects are produced and a pattern that “teaches” the person to repeat the rewarding behavior (using the drug) is set in motion.

As a person becomes addicted, his brain is exposed repeatedly and over a long period of time to higher and higher levels of the particular substance. In response, the brain attempts to adapt to the repeated intake of the substance. "It is called neuroadaptation, and it causes the brain to change in very specific ways," Willenbring explains. The person becomes less able to control his intake of alcohol or another drug of choice. "This is the very first symptom of an addiction: impaired control."

Willenbring calls the experience of impaired control the "waterslide," because once someone starts to sense that they might be using too much, they try to stop, but can’t. This tends to happen again and again. Addicts "repeatedly get onto the waterslide and try to get off halfway down, but they can’t," he explains. Setting limits (for example, deciding to use a certain amount or to use only at certain times), and then going over these limits, and spending more time consuming the substance even while wanting to quit are common behaviors for an addict.

The Progress of Addiction

While most people will not progress beyond this stage, which for drinkers is known as a mild to moderate alcohol use disorder, others go on to the next stage, in which consuming the drug of choice becomes automatic, Willenbring says.

As the pattern of abuse goes on, areas of the brain that are important for judgment, decision making, memory, learning, and behavior control are affected. When this happens, and thinking is impaired, the addict continues to search out and consume drugs, even though the consequences may be devastating.


Overcoming an addiction is possible, but some are harder to beat than others. With opioids such as heroin, for instance, the chance of a relapse is extremely high and a person may be offered a medication such as methadone to fight cravings and help lower the risk of relapse.

But addictions to legal substances can be extremely difficult to overcome, too: "Nicotine [in cigarettes] is one of the most addictive substances of all,” says Levin, who is chair of the American Psychiatric Association’s Council on Addiction Psychiatry. "Nicotine or anything else that is smoked reaches the brain very quickly. The route of administration and the speed with which substance gets to the brain are all factors that contribute to the development of addiction."

Wondering whether you or a loved one might have a problem with alcohol? The National Institute on Alcohol Abuse and Alcoholism has a variety of informational materials, including one article that shows you how to assess whether an Alcohol Use Disorder may be present. Download it here.

Frances Levin, MD, reviewed this article.


Levin,  Frances, MD. Phone interview on January 8, 2016.

Willenbring, Mark, MD. Phone interview on January 5, 2016.

"DrugFacts: Treatment Statistics." National Institute on Drug Abuse. Page last updated March 2011.

"Alcohol Facts and Statistics." National Institute on Alcohol Abuse and Alcoholism. March 2015.

"Overdose Death Rates." National Institute on Drug Abuse. Revised December 2015.

"DrugFacts: Understanding Drug Abuse and Addiction." National Institute on Drug Abuse. Revised November 2012.

"Drugs, Brains, and Behavior: The Science of Addiction." National Institute on Drug Abuse. Page last updated July 2014.

Wareham, Justin D. and Potenza, Marc N. "Pathological Gambling and Substance Use Disorders." National Institutes of Health. September 2010.

Nurnberger, John I, Foroud, Tatiana, et al. "Is There a Genetic Relationship Between Alcoholism and Depression?" Alcohol Research & Health 2002 26,3.