Traditionally, addiction referred to physical dependencies on drugs, alcohol, or other substances. Today, however, the term dependence is increasingly used for physical dependencies, while addiction is more often used for psychological dependencies. So habitual drug or alcohol use might be called dependence, while compulsive indulgence in an activity such as gambling, sex, or internet use might be termed an addiction.
The terms are used interchangeably in many contexts, however, and their medical meanings are in development. An earlier version of this post said that addiction was psychological and dependence was physical, and we were kindly corrected by a doctor who informed us that the distinction outlined above is the one used in medicine. Yet in searching nonmedical texts on the web, we find both words used for psychological and physical dependencies.
For all intents and purposes, dependence and addiction can be used interchangeably. For example, these sentences would mean the same if dependence were replaced with addiction or vice-versa:
Those recovering from drug and alcohol dependence might feel anxious about accepting invitations to events where alcohol is involved. [The Newark Advocate]
Depression symptoms increase over time for women in their 30s and 40s who are prone to addiction problems and antisocial behavior, researchers report. [U.S. News & World Report]
More than half of those questioned thought people with a history of drug dependence were a burden on society … [Glasgow Evening Times]
This came despite mountains of studies establishing that such tactics do children much more harm than good, increasing the risk of anxiety, depression and addiction. [NY Times]