Background. There has been a long-standing debate as to whether postpartum psychoses are distinct from other psychoses. While the outcomes of postpartum psychosis are in general thought to be good, the disorder is linked to a high rate of suicide.

Method. We have utilized a database of 3872 admissions to the North Wales Asylum during the period 1875–1924 to extract data on the prevalence, course and clinical features of postpartum psychoses during this period. We have collected first admissions for postpartum psychosis between 1994 and 2005 in North West Wales to establish a current incidence rate for the disorder.

Results. The incidence of psychoses with a first onset in the postpartum period in North West Wales has fallen in the modern period, while the incidence of postpartum psychoses in women with a pre-existing mental illness remains the same. Some features of the clinical picture and course of postpartum psychoses differ from other psychoses, but may be gender rather than disorder linked.

Conclusions. These findings suggest that psychoses with their first onset in the postpartum period may be vanishing. If replicated, this would support claims that these disorders are distinct from other disorders. Alternately, if regarded as affective disorders, establishing the basis for the apparent decline in frequency of these disorders may have implications for other affective disorders.