Postnatal Depression: An Evolutionary Approach

Postnatal depression, much like depression in general, is a horrendous, crippling condition. But it’s something that may have been developed over time to benefit our survival as a species in some way, shape or form.

As much as we like to think we’ve come a long way since our ancestors of the Neolithic era, in reality, we’re not that different. Of course, our technology has drastically changed, but underneath the gadgets and the gizmos we’re still pretty much the same animal.

This is an important point to keep in mind when we think about our innate behaviours, and more importantly in this post, postnatal depression. Now, it might seem a little bizarre at first as to why we would have adapted to give ourselves something as bad as depression, but when applied to the Parental Investment Theory (PI for short), it all makes a little more sense.

What Is Parental Investment Theory?

PI, in essence, is the weighing of the costs and benefits of allocating investment between oneself and the reproductive effort, such as raising a baby. Parents will have to size up their current situation and then decide between investing in themselves, their offspring or mating opportunities. This approach states that investment in a newborn baby is not necessarily an automatic choice as there will be certain circumstances in which investment will be too costly to the parent and hence one that they do not want to make.

Hagen (1999) argued that postnatal depression came as a signal for the mother to evaluate her situation and form a decision on whether to invest in the baby or herself. He suggested that postnatal depression could form as a result of one of the following things:

  1. There is insufficient investment from the father or others to successfully raise the offspring.

  2. There are problems with pregnancy, birth, or with the infant that indicate that this offspring may have low viability, that is, is unlikely to survive to reproductive age.

  3. Environmental conditions are poor for raising an offspring (e.g. harsh winter, insufficient resources).

  4. There are large opportunity costs-investment in the offspring precludes investment in other beneficial activities. In this case, investment directed toward the offspring would be more profitably directed toward: Existing offspring, the mother’s own survival, growth, and development, and thus her ability to invest in future offspring or finding a better mate.

This all makes perfect sense, and is even backed up with research, which has showed that increased maternal support resulted in lower levels of postnatal depression. It also indicates that traumatic births can results in a higher risk of PND.

So what’s the point in me telling you that postnatal depression could be seen as an evolutionary trait inbuilt into our survival mechanisms? Well, for a start, if we apply this method of thinking, it gives us a few solutions to the problem.

What we can do is ensure that a mother is well supported after the birth of a baby. This is why extended paternity leave really should be given, and why peer based parenting groups is something all new mothers should at least consider, even more so if they’re struggling.

These peer groups help to replicate the help that a mother would have received back in the caveman days. It’s a place to open up about problems and gain advice from people who have been through it all too.

As for traumatic births, there’s very little we can do to actually prevent them, well, perhaps there are, but this isn’t the blog to start talking about ways to help birth. When these births do occur more support should be given to mothers. Counselling sessions, more medical involvement and increased visits from health workers are all things that should be given if the birth is traumatic. Of course, trauma can often be a subjective experience, so it will often be determined by the mother.

Also, it’s important to note that if postnatal depression is a result of our genetics then we can feel like it’s not our fault for having it. It’s just a biological response to our environment. We shouldn’t feel bad for having it, it’s just something that’s written into our genetic code as a response to what we’ve been through. Anything that would’ve helped our survival back in the day has stuck around until now. There are many things we still do today that can be considered as harmful to us, but are merely here as a result of our survival, and postnatal depression, is just one of them.

Thanks for giving this a read, I know it’s a little bit different to all the rest of the talk on postnatal depression, and I dare say people won’t find it that interesting, but I always like to give a bit of balance and perspective to an argument. If you disagree with what’s been said here, or want to add anything, feel free to leave a comment, either here or on the Facebook page, or get involved on Twitter.


I’m a 27 year old married father of one – soon to be two! I started blogging after suffering with postnatal depression when Isabelle was born. These days I just talk about my life as a dad.

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