Psychosis is characterized by disturbance of thought, perception and emotions. Psychosis is a severe mental disorder which can be acute, transient, chronic or episodic, occurring as a primary disorder, such as schizophrenia, or as part of a mood disorder, such as depression or bipolar disorder, or secondary to conditions such as alcohol or drug abuse, medical illnesses (e.g. HIV/AIDS, cerebral malaria), or neurological disorders (e.g. dementia and stroke).

Worldwide, 25 million people suffer from schizophrenia, the most common psychotic disorder. Schizophrenia has a relatively low incidence but high prevalence. Despite severity, the evidence from low-income countries shows that treatment halves the chance of relapse of schizophrenia after one year, with up to 77% being relapse free. Considering this fact, psychosis is one of the priority conditions in the WHO mental health Gap Action Programme (mhGAP) and for inclusion in integrated mental health services for primary health care advocated by the regional strategy for mental health and substance abuse.