I recently came across a newspaper headline that made me reflect for a while.
Postpartum depression (PPD) is a severe form of the baby blues that affects between 10-20% of women. Anyone familiar with Sarah Blaffer Hrdy’s book Mothers and Others (2009) may even wonder why not more women are affected. In our hunter-gatherer pasts parenting was done by many people in the band, not only the mother and her closest kin. This is called alloparenting. This human practice is reflected in sayings like “It takes a village to raise a child.
Nowadays the village is gone and it is often the mother alone who bears the brunt of childcare and may therefore be easily overwhelmed and feel helpless. We should therefore expect an increase of PPD in women who feel socially isolated (not having enough support).
That said, we should even expect more women to suffer from PPD during isolation due to COVID, however only a minority is severely affected. In my model of human evolution these women would be mostly from the hunter-gatherer type (about 25%) of the population.
Early farmers and pastoralists relied more heavily on close kin to raise their children than hunter-gatherers. Therefore farmer-herder types should be less likely to suffer from PPD as long as they have the support of their closest kin. The same isn’t true for a hunter-gatherer type woman. She may feel unsupported and overwhelmed even though her partner and parents support her and her fears may seem irrational.
These hunter-gatherer type women are “neurodiverse” in the widest sense. If my hypothesis is correct we should be able to find this correlation to be true for all types of neurodiversity. In fact this is the case as this article from 2020 asserts:
Responses also showed that autistic mothers were more likely to find motherhood an isolating experience, to worry about others judging their parenting, and to feel unable to turn to others for support in parenting.
Of course, that in itself is little proof, as women with ASD often have a hard time taking care for themselves. So, it will be little surprising that women with ADHD also suffer from PPD more frequently. But what about this headline?
A neurodiverse mother might not be severely affected by ADHD, but her children may be. Also women who have a family history of bipolar are more frequently affected by PPD. So, it is not necessarily the woman herself who has to show symptoms of neurodiversity, but a relative, or even her child. This means that PPD is not exclusively dependent on the parenting abilities of a (neurodiverse) mother.
If my hypothesis is correct mothers with a different form of neurodiversity should also be affected: giftedness. Unfortunately, I wasn’t able to find any studies that showed a correlation between high IQ mothers and PPD. However, there may be indirect indications. Women with high IQ tend to delay childbirth (university, career), so older mothers should have higher rates of PPD than younger mothers. Indeed this is true:
A recent study from Canada has observed higher rates of depression in mothers who have children after the age of 40. The prevalence of depression after delivery was about threefold higher in women aged 40 to 44 years as compared to women aged 30 to 35 years.
A three times higher risk of PPD is definitely something that is in need of explanation and further research. The hunter-gatherer hypothesis may provide a good start.
This may have been a somewhat surprising post on my blog, but considering how central reproduction is to evolution it shouldn't really be a surprise.
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