The case of poor postpartum mental health: a consequence of an evolutionary mismatch–not of an evolutionary trade-off

Today's post is by Orli Dahan (Tel-Hai College) on her recent paper, "The case of poor postpartum mental health: a consequence of an evolutionary mismatch–not of an evolutionary trade-off" (Biology & Philosophy, 2023).

Orli Dahan

In my paper I criticize an evolutionary explanation to the phenomena of postpartum mood disorders and offer a different evolutionary explanation. These disorders develop shortly after childbirth in a significant proportion of women and have severe effects. I suggest that poor postpartum mental health is a classical mismatch situation: Namely, that a trait or function adaptive in a previous human environment becomes maladaptive in the modern environment. This is an argument used to explain many human health problems, such as diabetes and allergies. 

The evolutionary explanation that I reject is the ‘evolutionary trade-off’ explanation. According to it, poor postpartum mental health is a consequence of an evolutionary trade-off – a compromise of neurological changes in the maternal brain during pregnancy which, on the one hand, maintain pregnancy, and on the other, increase the likelihood for women after giving birth to develop psychopathology. 

I demonstrate that the trade-off explanation ignores the crucial event of childbirth. I elaborate on environmental features of childbirth, a physiological process that is substantially different in the current versus evolutionary childbirth and postpartum setting, and show that maternal brain neuroplasticity and biochemical alterations are not an evolutionary trade-off, but an adaptation. 

Additionally, the incidents of poor postpartum mental health are better viewed as a maladaptation of the typical modern environments – an evolutionary mismatch. Thus, the potential to suffer from poor mental health in postpartum is an external, dependent on contemporary childbirth and postpartum environments, and not due to any essential property women possess as a result of evolutionary compromise.

I argue that many women today are at risk for poor postpartum mental health, but not because it is an evolutionary trade-off. The approach of an evolutionary trade-off posits that there is something inherently not healthy in postpartum women: The tendency toward poor mental health is the price a woman must pay for becoming a mother. Instead, I argue that the physiological process of becoming a mother once included the triggering of feeling like a superwoman, but the modern birth setting and post-birth environment have turned this adaptation into the maladaptation we now face. 

Women after a physiological childbirth are probably adapted to feel euphoric pleasure and enhanced self-esteem – as a natural aid in adjusting to motherhood. However, most deliveries nowadays are not physiological deliveries, but highly medicalized and traumatic. Thus, unfortunately, the exceptional adaptation, in our current setting, became a maladaptation.

Furthermore, I claim that accuracy in use of evolutionary concepts is crucial for making good science, as well as for developing beneficial practices. Hypotheses have consequences for future research programs, psychological and medical treatments, prevention strategies, and intervention procedures. Thus, mere screening postpartum women at risk is insufficient. Distinguishing between evolutionary concepts (such as ‘evolutionary mismatch’ and ‘evolutionary trade-off’) in the context of pregnancy, birth, and motherhood is vital for developing more accurate preventions and interventions.