Alcohol is a sedative. Sedatives make people feel less anxious and more relaxed. But they also slow down physical reactions, and cause sleepiness or unconsciousness. A mixture of sedatives is dangerous because vital processes like the heartbeat get slower too. Sedatives may be addictive.
Caffeine is a stimulant.
They may hear, see and think things which are not really happening. People's experiences vary, just as dreams can be pleasant or nightmares. LSD is a hallucinogen. They stop people reacting to physical pain or emotional worries. Heroin is a painkiller.