What defines withdrawal in the context of drug use?

Withdrawal is specifically defined as the physiological and psychological symptoms that occur when a person who has been using a drug suddenly stops taking it. This happens because the body has become accustomed to the presence of the substance, and without it, various systems in the body may not function normally. Symptoms of withdrawal can include anxiety, tremors, nausea, and other unpleasant physical and mental effects, which signify that the body is reacting to the absence of the drug it has adapted to.

The other choices focus on different aspects of drug use, such as increased consumption, changes in cravings, or the efficacy of the drug, but they do not address the specific condition that arises from cessation of drug use that characterizes withdrawal. Understanding this concept is crucial for recognizing the challenges and potential dangers associated with stopping drug use after prolonged periods, which is a vital aspect of addiction and rehabilitation discussions.