Psychedelic drugs change the way people see, hear and think about things. They might see colours differently, or see objects change shape.
They will be aware of all this happening, and remember it vividly, even if it has been frightening. They may not be entirely in control of their actions whilst using this drug. This can put them, and others around them, in danger.
Different psychedelic drugs can have different effects on people. Sometimes people will react differently to the same drug, depending on how they are feeling, who they are with at the time and how strong the drug is.