Lindsay Clancy, a Massachusetts mother on trial for killing her three children, heard a commanding voice that told her to harm them, her defense argues—raising urgent questions about how postpartum psychosis is diagnosed, treated, and whether our mental health system failed her. Postpartum psychosis, affecting one to two per 1,000 births, causes paranoia, hallucinations, and delusions weeks after childbirth, yet remains unclassified in the DSM and is poorly understood by clinicians.