When someone becomes ill in this way and loses contact with reality it is called a psychotic episode. People who have experienced this often call it spinning out or going off the planet. With time and the right treatment, most people make a full recovery from the experience. Many may never have another episode. A minority experience psychotic symptoms on a daily basis.
Psychosis is most likely to occur in young adults and is quite common.
Around 3 out of every 100 people will experience a psychotic episode making psychosis more common than diabetes. Psychosis can happen to anyone. Like any other illness it can be treated. A number of theories have been suggested as to what causes psychosis, but there is still much research to be done. It may be a combination of factors.