Psychosis does not refer to a specific disease. It is a syndrome which is part of a group of very serious mental disorders in which some loss of contact with reality has occurred. This is reflected in the following symptoms:
- disturbances in perception (hallucinations, e.g. hearing voices or seeing things that are not there)
- bizarre or clearly unjustified beliefs and judgements (delusions, e.g. beliefs of being persecuted with no external evidence, or thoughts of people being able to read ones mind)
- disorganized thinking (speaking in ways that are confusing), or bizarre behaviour
Psychosis results from abnormalities in the brain, particularly at the level of the chemical messenger systems, such as dopamine and serotonin. Many specific diseases are included in the term psychosis: schizophrenia, schizophreniform, schizo-affective, and less commonly, manic-depressive and drug-induced psychoses. The exact cause of each of the psychotic disorders is unknown. However, a number of risk factors (such as family history of psychosis) have been well established.
Well over 1% of the population will develop a psychotic illness sometime in their lifetime. Young people (men age 16-25 and women 16-35) are at particularly high risk. The risk is further increased with positive family history of a similar condition, and illicit drug abuse (including cannabis). An individual at risk can have the first episode of psychosis triggered by even mild use of illicit drugs, excessive alcohol use, or stress. Individuals with all levels of intelligence and from all social backgrounds can be affected by psychosis.