Final answer:
Continuing use despite medical or psychological reasons to stop is a sign of drug addiction.
Step-by-step explanation:
Drug addiction refers to the compulsive use of a drug despite the negative consequences that such use may entail. It is characterized by the inability to stop using the drug despite medical or psychological reasons to do so. This can include physical and/or psychological dependence on the drug.
An example of this would be someone who continues to use a psychoactive drug even though it is causing significant physical or psychological harm.