How do tolerance and dependence contribute to alcohol use disorder?

Tolerance and dependence are physiological processes that significantly contribute to the development and progression of alcohol use disorder (AUD).

• Tolerance: This occurs when the body becomes less responsive to alcohol over time, requiring larger or more frequent doses to achieve the same effects. As an individual’s tolerance increases, they may consume greater quantities of alcohol, which heightens the risk of adverse health consequences and reinforces patterns of excessive use.123
• Dependence: This is a physiological state where the body adapts to the regular presence of alcohol, integrating it into normal biological functioning. When an individual is dependent, their brain and body rely on the substance to maintain stability. If alcohol intake is reduced or stopped, the body experiences withdrawal symptoms—such as nausea, shaking, or restlessness—which often drive the individual to continue drinking to avoid this distress.45

While distinct, these factors often occur together in the context of AUD, creating a cycle where the body’s need for the substance and the diminished effect of previous doses make it increasingly difficult for an individual to control or cease their intake.415