The cause of Brief Psychotic Disorder is still being studied but it seems to be due to a stressful or traumatic event in the patient's life. Such traumatic onsets can vary, and some examples include:

• If someone experiences an extremely stressful event that anyone would find traumatic, that is considered a marked stressor. Examples include: death, natural disasters, time in the military, and immigration. These patients are considered to have brief reactive psychosis.
• On the other hand, if their symptoms begin without marked stressors, they're considered to have brief psychotic disorder.
• Brief psychotic disorder can also stem from giving birth. In this case, symptoms would be present within the four weeks postpartum.

However, genetic, neurological, or environmental components may also play a role in the development of BPD.