[4] There are three forms of brief psychotic disorder:[5] Brief reactive psychosis (designated since the DSM IV-TR as "brief psychotic disorder with marked stressor(s), BRP"), is the psychiatric term for psychosis which can be triggered by an extremely stressful event in the life of an individual and eventually yielding to a return to normal functioning.

[6] Brief reactive psychosis generally follows a recognisably traumatic life event like divorce or homelessness,[7] but may be triggered by any subjective experience which appears catastrophic to the person affected.

[8] Among such stressors are the death of a loved one, professional loss such as unexpectedly losing one's job or otherwise becoming unemployed, or serious adverse changes in the patient's personal life, such as the breakdown of their family through divorce, etc.

[9] The condition usually resolves spontaneously within a time span of weeks to months, with the severity of the symptoms reducing continuously over the period in question.

Another theory suggests that the disorder is caused by poor coping skills, as a defense against or escape from a particularly frightening or stressful situation.

In females, a low estrogen state (which may occur premenstrual, postpartum, or perimenopausal) can trigger sudden, short-lived psychosis.

[3] There are general medical causes of brief psychosis that should be considered during evaluation, including postnatal depression, HIV and AIDS, malaria, syphilis, Alzheimer's disease, Parkinson's disease, hypoglycaemia (an abnormally low level of glucose in the blood), lupus, multiple sclerosis, brain tumor, SARS-CoV-2 (COVID-19) infection and pediatric autoimmune neuropsychiatric disorders (PANS).