The Science of Drug Abuse and Addiction: The Basics
What is drug addiction?
Addiction is defined as a chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences. It is considered a brain disease because drugs change the brain; they change its structure and how it works. These brain changes can be long lasting and can lead to many harmful, often self-destructive, behaviors.
Why study drug abuse and addiction?
Abuse of and addiction to alcohol, nicotine, and illicit and prescription drugs cost Americans more than $700 billion a year in increased health care costs, crime, and lost productivity.1,2,3 Every year, illicit and prescription drugs and alcohol contribute to the death of more than 90,000 Americans, while tobacco is linked to an estimated 480,000 deaths per year.4,5 (Hereafter, unless otherwise specified, drugs refers to all of these substances.)
How are drug disorders categorized?
NIDA continues to use the term “addiction” to describe compulsive drug seeking despite negative consequences. However, “addiction” is not considered a specific diagnosis in the fifth edition of The Diagnostic and Statistical Manual of Mental Disorders (DSM-5)—a diagnostic manual used by clinicians that contains descriptions and symptoms of all mental disorders classified by the American Psychiatric Association (APA).
In 2013, APA updated the DSM, replacing the categories of substance abuse and substance dependence with a single category: substance use disorder. The symptoms associated with a substance use disorder fall into four major groupings: impaired control, social impairment, risky use, and pharmacological criteria (i.e., tolerance and withdrawal).
The new DSM describes a problematic pattern of use of an intoxicating substance leading to clinically significant impairment or distress, as manifested by at least two of the following, occurring within a 12-month period:
- The substance is often taken in larger amounts or over a longer period than was intended.
- There is a persistent desire or unsuccessful effort to cut down or control use of the substance.
- A great deal of time is spent in activities necessary to obtain the substance, use the substance, or recover from its effects.
- Craving, or a strong desire or urge to use the substance.
- Recurrent use of the substance resulting in a failure to fulfill major role obligations at work, school, or home.
- Continued use of the substance despite having persistent or recurrent social or interpersonal problems caused or exacerbated by the effects of its use.
- Important social, occupational, or recreational activities are given up or reduced because of use of the substance.
- Recurrent use of the substance in situations in which it is physically hazardous.
- Use of the substance is continued despite knowledge of having a persistent or recurrent physical or psychological problem that is likely to have been caused or exacerbated by the substance.
- Tolerance, as defined by either of the following:
- A need for markedly increased amounts of the substance to achieve intoxication or desired effect.
- A markedly diminished effect with continued use of the same amount of the substance.
- Withdrawal, as manifested by either of the following:
- The characteristic withdrawal syndrome for that substance (as specified in the DSM- 5 for each substance).
- The substance (or a closely related substance) is taken to relieve or avoid withdrawal symptoms.
Please Note: Current national surveys of drug use have not yet been modified to reflect the new DSM-5 criteria of substance use disorders and therefore still report substance abuse and dependence separately.
How does NIDA use the terms drug abuse and addiction?
People use substances for a variety of reasons. It becomes drug abuse when people use illegal drugs or use legal drugs inappropriately. This includes the repeated use of drugs to produce pleasure, alleviate stress, and/or alter or avoid reality. It also includes using prescription drugs in ways other than prescribed or using someone else’s prescription. Addiction occurs when a person cannot control the impulse to use drugs even when there are negative consequences—the defining characteristic of addiction. These behavioral changes are also accompanied by changes in brain functioning, especially in the brain’s natural inhibition and reward centers. NIDA’s use of the term addiction corresponds roughly to the DSM definition of substance use disorder. The DSM does not use the term addiction.
What is the difference between physical dependence, dependence, and addiction?
Physical dependence is not equivalent to dependence or addiction, and may occur with the regular (daily or almost daily) use of any substance, legal or illegal, even when taken as prescribed. It occurs because the body naturally adapts to regular exposure to a substance (e.g., caffeine or a prescription drug). When that substance is taken away, symptoms can emerge while the body re-adjusts to the loss of the substance. Physical dependence can lead to craving the drug to relieve the withdrawal symptoms. Drug dependence and addiction refer to substance use disorders, which may include physical dependence but must also meet additional criteria.
How do drugs work in the brain to produce pleasure?
Nearly all addictive drugs directly or indirectly target the brain’s reward system by flooding the circuit with dopamine. Dopamine is a neurotransmitter present in regions of the brain that regulate movement, emotion, cognition, motivation, and feelings of pleasure. The overstimulation of this system, which rewards our natural behaviors, produces the euphoric effects sought by people who use drugs and teaches them to repeat the behavior.
Is drug abuse a voluntary behavior?
The initial decision to take drugs is mostly voluntary. However, when addiction takes over, a person’s ability to exert self-control can become seriously impaired. Brain-imaging studies from people addicted to drugs show physical changes in areas of the brain that are critical for judgment, decisionmaking, learning, memory, and behavior control. Scientists believe that these changes alter the way the brain works and may help explain the compulsive and destructive behaviors of an addicted person.
Can addiction be treated successfully?
Yes. Addiction is a treatable, chronic disease that can be managed successfully. Research shows that combining behavioral therapy with medications, where available, is the best way to ensure success for most patients. Treatment approaches must be tailored to address each patient’s drug use patterns and drug-related medical, psychiatric, and social problems.
Does relapse to drug use mean treatment has failed?
No. The chronic nature of addiction means that relapsing to drug use is not only possible but also likely. Relapse rates are similar to those for other well-characterized chronic medical illnesses such as diabetes, hypertension, and asthma, which also have both physiological and behavioral components. Treatment of chronic diseases involves changing deeply imbedded behaviors. For the addicted patient, lapses back to drug use indicate that treatment needs to be reinstated or adjusted, or that alternate treatment is needed.
How many people die from drug use?
The Centers for Disease Control and Prevention (CDC) report that there were more than 40,000 unintentional drug overdose deaths in the United States in 2011, a 118-percent increase since 1999. More than 22,000 people die every year from prescription drug abuse,6 more than heroin and cocaine combined.7
Source: McLellan et al., JAMA, 284:1689-1695, 2000.
1. National Drug Intelligence Center. The Economic Impact of Illicit Drug Use on American Society. Washington, DC: United States Department of Justice, 2011.
2. Rehm J, Mathers C, Popova S, Thavorncharoensap M, Teerawattananon Y, Patra J. Global burden of disease and injury and economic cost attributable to alcohol use and alcohol-use disorders. Lancet 373(9682):2223-2233, 2009.
3. Centers for Disease Control and Prevention. Best Practices for Comprehensive Tobacco Control Programs — 2014. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014.
4. Centers for Disease Control and Prevention (CDC). Alcohol-Related Disease Impact (ARDI). Atlanta, GA: CDC.
5. U.S. Department of Health and Human Services. The Health Consequences of Smoking—50 Years of Progress: A Report of the Surgeon General. Atlanta, GA: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention, National Center for Chronic Disease Prevention and Health Promotion, Office on Smoking and Health, 2014.
6. Centers for Disease Control and Prevention. Prescription Drug Overdose in the United States: Fact Sheet. Available at: www.cdc.gov/homeandrecreationalsafety/overdose/ facts.html. Last accessed: September 15, 2014.
7. Centers for Disease Control and Prevention. Prescription Painkiller Overdoses in the US. Available at: www.cdc.gov/vitalsigns/PainkillerOverdoses/index.html. Last accessed: September 15, 2014.