Understanding Dependence, Addiction, & Tolerance

Dependence occurs as a result of physiological adaptations to chronic exposure to a drug. Those who are dependent on a substance will experience unpleasant physical withdrawal symptoms when they abruptly reduce or stop use of the drug. These symptoms can be mild to severe (depending on the drug) and can usually be managed medically or avoided by slowly tapering down the drug dosage. Dependence is often a part of addiction, but they are not equivalent.

Addiction involves other changes to brain circuitry and is distinguished by compulsive drug seeking and use, despite negative consequences.

Tolerance, or the need to take higher doses of a substance to get the same effect, often accompanies dependence. When tolerance to a prescription drug occurs, it can be difficult for a physician to evaluate whether a patient is developing a drug problem or has a medical need for higher doses to control his or her symptoms. For this reason, physicians should be vigilant and attentive to their patients’ symptoms and level of functioning and should screen for substance misuse when tolerance or dependence is present.