What defines physical dependence on a drug?

Physical dependence on a drug is primarily characterized by the presence of withdrawal syndrome when the drug is discontinued or reduced. This occurs because the body has adapted to the presence of the drug, and its sudden absence can lead to various physiological and psychological symptoms. These withdrawal symptoms can range from mild to severe, depending on the substance and the degree of dependence developed.

The concept of physical dependence highlights the body's reliance on the drug to maintain normal functioning, which is why withdrawal symptoms are a key indicator. The presence of these symptoms signals that the body has become accustomed to the drug's effects and reacts negatively when those effects are removed.

Understanding physical dependence is crucial for identifying individuals who may require treatment and support, as withdrawal can be a significant barrier to quitting use of the substance. In contrast, the other options describe aspects that do not directly define physical dependence. For instance, absence of withdrawal symptoms indicates no physical dependence, while psychological craving and absence of tolerance pertain more to other aspects of substance use and addiction without specifically indicating physical dependence.