Stimulants result in a feeling of energy and are sometimes called “uppers” because of this result. They stimulate your brain/body, hence the name. Depressants, on the other hand, slow your brain and body down, and for this reason, are called “downers.” Opium-related painkillers lessen pain, but also can lead to euphoria (the “high” feeling), sluggishness, or “relaxed” muscles. Hallucinogens make you hallucinate, which is when you perceive images, sights, and sometimes even smells that are not truly there.