Psychosis is a condition that affects the way your brain processes information. It causes you to lose touch with reality. You might see, hear, or believe things that aren’t real. Psychosis is a symptom, not an illness. A mental or physical illness, substance abuse, or extreme stress or trauma can cause it.

Psychotic disorders, like schizophrenia, involve psychosis that usually affects you for the first time in the late teen years or early adulthood. Young people are especially likely to get it, but doctors don’t know why. Even before what doctors call the first episode of psychosis (FEP), you may show slight changes in the way you act or think. This is called the prodromal period and could last days, weeks, months, or even years.

Sometimes you can lose touch with reality even when you don’t have a primary psychotic illness such as schizophrenia or bipolar disorder. When this happens, it's called secondary psychosis.

These episodes stem from something else, like drug use or a medical condition. Whatever the reason, they tend to disappear in a short time, and they often stay away if you treat the condition that caused them.