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Rare is Relative

Written by Teresa Twomey
Edited by Cheri Wissmann


So far in our blog series, we’ve discussed why calling PPP “rare” is harmful to our advocacy efforts, and also why “rare” is redundant in statements that include a rate of occurrence.


Based on how universal the use of the word “rare” has become when describing postpartum psychosis*, it seems that many consider “rarity” a basic fact about this illness.


But “rare” is not a stand-alone descriptor. It is a word that describes relationships.


Where there are rare things, there are also things that are more common.


Rare is relative.


Let’s dive into some examples of how similar rates of occurrence are described. This can provide some context about how word choice isn’t so much reflective of numerical frequency, but reflects how an author chooses to present their subject.


Down Syndrome occurs in about 1 of every 700 babies born. The CDC calls it “the most common chromosomal condition diagnosed in the United States.”1


Medline states that, “[c]ystic fibrosis is a common genetic disease within the white population in the United States . . . [that] occurs in 1 in 2,500 to 3,500 white newborns.”2 One research article further states that it has “traditionally been defined as the most common life-threatening inherited disorder of children in Caucasian populations.”3


Cerebral palsy, called by the CDC the “most common motor disability in childhood,” has global prevalence estimates “ranging from 1 to nearly 4 per 1,000 live births or per 1,000 children.”4


These all have rates similar to, or even less common, than even the conservative estimates used to describe postpartum psychosis. Yet government agencies and medical journals alike have made the deliberate choice to describe them as “common.”


Rare isn’t a fact – it’s a descriptor that can be applied to convey the relative importance of a subject.

To extend this example to postpartum psychosis, an author could choose to introduce this illness with a statement like,

“Postpartum psychosis is the most common psychiatric emergency associated with childbearing.”

When considering the subject of perinatal mood and anxiety disorders, there has been considerable effort made by advocacy groups to adopt language that serves to normalize these mental illnesses. This language encourages inclusion and compassion instead of segregation and “othering.”


For example, Postpartum Support International (PSI), the leading organization on perinatal mood and anxiety disorders in the US, currently shares the statistic that 1 out of 7 mothers will experience depression or anxiety, and that the #1 complication of pregnancy is depression.


This normalization, however, has not included pregnancy and postpartum psychosis until recently.


In July 2022, at the PSI annual conference, Teresa Twomey presented the case against the use of the word “rare” to describe PPP in her breakout session, “Perinatal Psychosis: Lessons Learned in a Life of Advocacy.” In the months following that talk, PSI and a few other organizations began removing “rare” from their websites and literature.


This was a big step in the right direction, but overall, postpartum psychosis is still prominently, regularly, and almost universally referred to as “rare.”

The outcome of this language is that perinatal psychosis serves as a foil for the other PMADs – where the presentation of psychosis as “rare” contrasts with and highlights the more “normal” or “common” PMADs. This increases a sense of isolation, shame, and stigma for those who suffer from psychosis during the perinatal period.


Rare is relative and calling postpartum psychosis “rare” is a choice that does not serve the population affected.


So please, stop calling it “rare.”


1Facts About Down Syndrome. Centers for Disease Control and Prevention: Birth Defects. (accessed 3/27/2022)

2Cystic Fibrosis: Frequency. National Library of Medicine, Medline Plus. (accessed 3/27/2022)

3Scotet, Virginie, Carine L’Hostis, and Claude Férec. “The Changing Epidemiology of Cystic Fibrosis: Incidence, Survival and Impact of the CFTR Gene Discovery.” Genes 11.6 (2020): 589. Web.

4Data and Statistics for Cerebral Palsy. Center for Disease Control and Prevention: Cerebral Palsy. (accessed 3/27/2022)


*A note about terminology: Pregnancy and Postpartum Psychosis Awareness Day aims to be inclusive in the way we spread awareness, as well as within the survivor community that we are building. That’s why we choose to use terms like “pregnancy and postpartum psychosis” or “perinatal psychosis,” rather than “postpartum psychosis.”


But when talking about rates of occurrence, the terms we use will reflect the scope of the research used in creating those estimates.


Nearly all research has focused on episodes of psychosis that occur immediately following childbirth and up to 3 months postpartum. It is not accurate to use those research findings to describe the prevalence of psychosis across the full perinatal period – which spans from conception until 1 year postpartum. 

A future blog post will provide more details about the limitations of current research, and will be linked here once it’s published. Stay tuned!

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