Which of the following is a depressant?

• A. Caffeine
• B. LSD
• C. Cocaine
• D. Alcohol

Answer: (D)

A depressant slows brain activity and bodily functions. Alcohol does this by dampening the central nervous system, which leads to slower reaction times, reduced coordination, and impaired judgment—exactly the kinds of effects that make driving after drinking dangerous. It works by boosting the inhibitory signaling of GABA and by reducing excitatory signaling from glutamate, so neural activity slows overall.

Caffeine, LSD, and cocaine are not depressants. Caffeine is a stimulant that increases alertness by blocking adenosine receptors. LSD is a hallucinogen that alters perception. Cocaine is a powerful stimulant that speeds up the nervous system and heart rate. Since they increase or alter activity rather than slow it, they aren’t depressants.