Postpartum psychosis: A very serious mental illness that can affect a new mother. The episode of psychosis usually begins within 1 to 3 months of delivery. A woman with postpartum psychosis may lose touch with reality and have auditory hallucinations (hearing things that are not actually happening, like a person talking) and delusions (perceiving things differently from the way they are). Visual hallucinations ((seeing things that are not there) are less common. Other symptoms may include insomnia, agitation, anger, and irrational guilt about somehow having done something wrong. Women who have postpartum psychosis need prompt treatment and almost always need medication. If they are at risk for hurting themselves or someone else, women with postpartum psychosis need to be in a hospital.