Commentary: postpartum psychosis, infanticide, and insanity--implications for forensic psychiatry.

Two dozen nations have infanticide laws that decrease the penalty for mothers who kill their children of up to one year of age. The United States does not have such a law, but mentally ill mothers may plead not guilty by reason of insanity. As in other crimes, in addition to the diagnosis of a mental disorder, other factors, such as knowledge of wrongfulness and motive, are critical to the assessment. Postpartum psychosis has been described for 2,000 years and modern science supports a genetic component to the risk. Yet, the Diagnostic and Statistical Manual of Mental Disorders does not include it as a diagnosis, leading to difficulty in testimony. In this article, we discuss postpartum psychosis, infanticide law, and research regarding mothers who kill, and we make recommendations to forensic psychiatrists.