Excerpt from "What is PND"
Chapter 4 - When your Blessings Don't Count by Linda Lewis

There are three types of mood disturbance that could follow childbirth and they are frequently confused or inadequately grouped together under the heading of postnatal depression. These syndromes can be seen as existing on a spectrum where the mildest condition is the “blues” and the most severe condition is postnatal psychosis. Postnatal distress falls somewhere between these two and is distinctly different in terms of onset, severity, duration and treatment.