What substances cause users to perceive things differently than they appear to others?

Hallucinogens are substances that significantly alter perception, mood, and various cognitive processes. They can cause users to experience sensations, thoughts, or feelings that do not align with reality, meaning that users may perceive visual or auditory stimuli that are not present or interpret them in a manner that deviates from how others perceive the same stimuli. This altered state can lead to experiences often described as "trips," where individuals may see colors more intensely, hear sounds differently, or have distorted sense of time and space.

In contrast, stimulants primarily increase alertness and energy; opioids mainly relieve pain and can induce feelings of euphoria but do not typically alter perception in the way that hallucinogens do. Depressants generally reduce central nervous system activity, leading to slowed responses and impaired judgment, rather than altering perception outright. Thus, hallucinogens are distinct in their ability to change the perception of reality itself, making them the correct answer to this question.