They may have a sense of overwhelming fear, sadness, and horror, or they may feel intense love and joy. During a trip, drug users may feel that they have gained a new understanding of God, the universe, and themselves. The effects of hallucinogenic drugs last from one hour to several days. But these effects may appear again months later as a flashback. People may feel unusually happy or upset for weeks after using hallucinogenic drugs.
Some users become mentally ill.
A trip and its effects vary from person to person and from trip to trip. Hallucinogenic drugs are not addicting, but some scientists believe they cause birth defects. Hallucinogenic drugs may someday prove useful to science. Scientists have used them to study the chemistry of the brain. Physicians have used the drugs experimentally to treat emotional disorders.