Only experienced by one or two women out of 1,000, postpartum psychosis (PPP) is a rare and extreme form of postpartum mood disorders and is seen in women who lose touch with reality shortly after birth. Usually occurring during the first three months after childbirth, women with PPP are often misdiagnosed with postpartum depression (PPD), a less severe form of PPP. The defense attorneys for Andrea Yates—in her highly publicized 2001 case about the drowning of her five young children in a bathtub—built a case around PPP. Yates was later found not guilty by reason of insanity and committed to a Texas state mental hospital.

The number of women with PPP has not changed since it was first recognized as a disorder in 1850. PPP is ...