A psychosis describes a state of mind where there is a loss of contact with reality, and clear distortions in thinking and reasoning. When someone experiences a psychosis, this is called a psychotic episode, and a psychotic episode can occur as part of a number of different disorders, e.g. schizophrenia; as a drug induced state; in affective illnesses - depression or mania; and where there is an established physically defined brain disease - including brain tumours or even epilepsy.

A psychotic episode is a frightening and confusing event for the individual experiencing it, and for their loved ones. Approximately three in every one hundred people will experience a psychosis, and a psychotic episode usually first occurs between the ages of 15 and 35 years. Sometimes a psychotic episode has a rapid onset (a few days), but often the onset of psychotic episode is more gradual, over a period of weeks or months.

When the onset is more gradual, individuals and their families will often report that things 'weren't quite right' for some time before the psychotic episode. A psychotic episode always requires treatment, and studies have shown that the earlier that treatment is obtained, the better the outcome for the individual.