Which of the following is NOT an example of a depressant?

Caffeine is not classified as a depressant; it is actually a stimulant. Depressants are substances that slow down the function of the central nervous system, leading to a calming effect and decreased physiological activity. Alcohol, barbiturates, and Valium all fall into this category as they induce relaxation, reduce anxiety, and can impair cognitive and motor functions.

Caffeine, on the other hand, increases alertness and energy by blocking the action of adenosine, a neurotransmitter that promotes sleep and relaxation. Instead of slowing down brain function, caffeine enhances alertness and can lead to increased heart rate and anxiety in higher doses. This fundamental difference in how these substances affect the central nervous system clearly distinguishes caffeine from the other options listed, which are all designed to depress or calm the body’s functions.