What is the primary characteristic of physical dependence on a drug?

The primary characteristic of physical dependence on a drug is demonstrated through the presence of withdrawal symptoms when the drug is not used. When an individual has developed physical dependence, their body adapts to the continuous presence of the substance, leading to a physiological state that relies on the drug for normal functioning. If the drug is suddenly reduced or stopped, the body reacts negatively, resulting in various withdrawal symptoms that can range from mild to severe. These symptoms are indicative of the body’s adaptation to the drug and highlight the physical aspects of dependence.

Other aspects of drug use, such as altered behavior or increasing dosage leading to enhanced effects, might be present but are not the defining feature of physical dependence itself. Hence, the presence of withdrawal symptoms is the hallmark that signifies a physical dependence on the substance.