Physical dependence is best defined as:

Physical dependence is characterized primarily by the body’s adaptation to a substance, leading to withdrawal symptoms when the substance is not present. This phenomenon occurs because the body has become accustomed to functioning in the presence of the substance, resulting in physiological changes. When use of the substance ceases, the individual may experience various symptoms, which can range from mild discomfort to severe, life-threatening reactions, depending on the substance and the level of dependence.

This definition highlights the importance of withdrawal symptoms as indicators of physical dependence. While needing to increase the dose, having a strong desire for a substance, or difficulties in managing social relationships may be related to substance use or addiction, they do not specifically pinpoint the physiological aspect that defines physical dependence. Hence, the presence of withdrawal symptoms is a clear and definitive marker that distinguishes physical dependence from other forms of substance-related issues.