2. Depresents Depressants are substances which slow down the normal function of the central nervous system, and are among the most widely used drugs in the world. These drugs include barbiturates, benzodiazepines, and alcohol. Marijuana and some inhalants are also depressants.
3. Stimulants Stimulants is a name given to psychoactive drugs that tend to increase activity in the brain. These types of drugs can temporarily elevate alertness, mood and awareness. Some stimulants are caffeine, nicotine, cocaine and methamphetines.
4. Hallucinogens Hallucinogens are strong mood-changing and they have the ability to cause changes in a person's perception of reality. Some Hallucinogen drugs are marijuana, LSD, mushrooms and mescaline.
