Understanding Tolerance, Dependence, and Addiction

It is important to understand the meaning of the terms tolerance, dependence, and addiction when discussing substance abuse and the use of prescription medications such as opioid painkillers.

What Is Tolerance?

Tolerance is defined as a person’s diminished response to a drug that is the result of repeated use ¹. People can develop tolerance to both illicit drugs and prescription medications. As stated above, tolerance is a physical effect of repeated use of a drug, not necessarily a sign of addiction. For example, patients with chronic pain frequently develop tolerance to some effects of prescription pain medications without developing an addiction to them.

What Is Dependence?

The words dependence and addiction are often used interchangeably, but there are important differences between the two. In medical terms, dependence specifically refers to a physical condition in which the body has adapted to the presence of a drug. If an individual with drug dependence stops taking that drug suddenly, that person will experience predictable and measurable symptoms, known as a withdrawal syndrome

What Is Addiction?

According to the National Institute on Drug Abuse (NIDA), addiction is a “chronic, relapsing brain disease that is characterized by compulsive drug seeking and use, despite harmful consequences” ⁷. In other words, addiction is an uncontrollable or overwhelming need to use a drug, and this compulsion is long-lasting and can return unexpectedly after a period of improvement.

The most important distinction between these concepts is that tolerance and dependence refer to the physical consequences of drug use. In contrast, addiction is a descriptive term that refers to a need to engage in harmful behavior.

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