Which statement correctly differentiates tolerance, dependence, and withdrawal?

• A. Tolerance is a reduced response requiring higher doses; dependence is a physiological adaptation with withdrawal symptoms when use stops; withdrawal includes tremors, anxiety, and autonomic changes when intake is reduced or stopped.
• B. Tolerance means increased sensitivity; dependence means no withdrawal; withdrawal is a craving only.
• C. Tolerance means withdrawal occurs quickly; dependence means you can't stop; withdrawal is purely psychological.
• D. Tolerance is a physiological need to drink more to avoid headaches; dependence is a state of craving with no physical symptoms.

Answer: (A)

Tolerance arises when the body adapts to regular drug exposure, dampening the effect so the same dose produces a weaker response and people often need larger amounts to achieve the same effect. Dependence is an adaptive state of the brain and body that makes normal functioning rely on the drug; when use stops or is reduced, withdrawal symptoms appear as the body readjusts. Withdrawal is the collection of physical and psychological symptoms that occur during reduced intake or cessation after dependence has developed, such as tremors, anxiety, sweating, and autonomic changes. These ideas fit together but describe different aspects: tolerance is about needing more to feel the same effect, dependence is the body’s adaptation to continuous use, and withdrawal is the symptom set that happens when stopping after dependence. The other statements mix up sensitivity, the nature of withdrawal, or whether symptoms are physical vs. psychological, which is why they’re not correct.