The evolution of depression

 

Psychological disorders such as depression have always been a difficult area for evolutionary psychology. Many disorders are incredibly detrimental to the survival of the individual, as well as their ability to reproduce. This is the opposite of what evolution is driven by.

So we have to ask what the reason for these traits to persist is. Most mutations in evolution tend to have a cost benefit balance, where the benefit outweighs the cost and that is why it persists. 

There are three main ways that a seemingly negative trait will persist. The first is that there are hidden benefits to the trait that ultimately outweigh the negative. For example, there may be more prolific reproduction at the cost of the individuals’ life. 

The second is that the benefit and cost are only indirectly related through the mutation. The ultimate benefit is greater than the loss. For example, walking on two legs makes us slower in short distances but ultimately faster in longer distances.

The third way is that an adaptation which is beneficial in certain circumstances becomes maladaptive in a different environment. If the organism remains in the new environment, this trait usually gets selected out over time. However if the organism moves between environments, not enough time has passed or the trait isn’t detrimental enough, it may persist.  

This begs the question, what are the benefits to a disorder like depression that it may outweigh the negative aspects of it? 

 

Is it helpful to dwell on a problem?

 

The rumination hypothesis states that we have evolved to go into very deep rumination cycles when faced with extremely complex problems. If we have intense challenges to face that we are struggling to overcome, our bodies close off from the world around us to focus on that single problem.

One of the most common experiences of depression is anhedonia, the inability to enjoy things we once did. Equally we tend to close off and shut down from the world around us. It feels like you’re unable to get out of your own head and focus on anything else. 

Through this, we spend our time going over the major problems we are facing, running through our minds again and again. The idea behind the rumination hypothesis is that through this process we will eventually come to an answer. That we are shutting away from distractions to focus on the main problems to make real changes to our situation.

When I think back to my own experiences, I can relate to this idea quite well. During difficult periods, particularly if there was one main issue I was dealing with. If I spent a deliberate time and effort thinking about the issues, it would often result in novel solutions. 

The biggest caveat to this is that it only really worked out that way in very mild cases. If I were unable to solve the problem or there were multiple problems that became overwhelming, these episodes of depression dragged on and progressively got worse. 

When I couldn’t solve a problem or felt powerless to make the changes, that constant rumination only made things worse. In fact it becomes very draining and quickly debilitating due to shutting out other influences. 

 

Where does it all fall apart?

 

There are a number of physical effects that occur in a depressed person. To simplify, there is an over activation of the sympathetic nervous system. This system increases heart rate, alters hormonal levels and sends more blood to your muscles. It prepares us for the fight or flight response. 

It may be that the activation of this system evolved to help us focus on complex problems. However, if this system is constantly being fired then it will cause a lot of negative effects in turn. This is common for many areas of our physiology. Inflammation for example is beneficial to blood flow temporarily helping recovery but of course causes damage in prolonged exposure. 

So as we experience prolonged heightened activation of the sympathetic nervous system there are many side effects. Hunger will change as will weight through hormonal changes. Sleep can become heavily disrupted and you become fatigued, because your body is constantly in this fighting state. 

All of these effects will then make it harder to concentrate. Our physiological changes that temporarily allow for superior rumination quite quickly start to degrade our ability to concentrate at all.

 

What’s the alternative?

 

This has fueled the counter argument that depression is a maladaptive trait and that rumination should be avoided rather than embraced. Metacognitive therapy was developed under this viewpoint, the main premise being that rumination is counter productive.

There are a number of reasons that a maladaptive trait can persist in a population. Equally many adaptations can become maladaptive in different circumstances. The metacognitive viewpoint suggests that rumination is ultimately maladaptive. Therapy should be aimed at teaching people to stop the rumination cycle rather than embracing it. 

Once again I think back to some of the worst periods of my life. When depression wasn’t just a mild episode but a prolonged period of severity. One of the main reasons I got out of that dark place was because I realised I wasn’t getting anywhere. I needed to make a physical change, my environment, my situation, my focus.

Something new, something completely different which often gave me a new frame of reference to then rebuild my life around. It was these moments that ultimately led to me getting out of that place of depression. 

I don’t want to write off the rumination hypothesis or the idea that there are adaptive benefits to some psychological disorders. However it probably developed early on in our evolutionary past when complex problems weren’t all that complex by today’s standards. 

We are also constantly bombarded with information. Social position is often dictated by social media platforms. It may simply be the adaptation becomes maladaptive due to the environments we live in and the complexity of problems we face. 

There are records of depression dating back to the ancient Greeks, it wouldn’t be correct to say modern technology is the cause. However, it may be making it worse or more prolific than ever before.

 

Where does that leave us?

 

Cognitive behavioural therapy has consistently been shown to be one of the best therapeutic practices for depression. It is heavily influenced by the idea that we should consider our thoughts and often challenge how we think. 

Considering how successful it has been, there is definitely still a place for rumination. A place for deep thought and taking time to ourselves to focus inwardly. Mindfulness and meditation can follow this practice in a similar way. 

However it is also clear that people can become trapped within those cycles of thought. That these techniques might ultimately prolong recovery by making us focus on those recurring thoughts. Perhaps we recover because we’ve challenged our thoughts so much we no longer dwell on the original one.

Metacognitive therapy is still relatively new but has shown a lot of success. In situations where depression has become prolonged, it is probably better to take on some of those practices. Step away from the whole situation and train ourselves to stop rumination completely. 

I think the best approach is to embrace both sides to an extent. Once comfortable with both approaches we can select which one feels most appropriate to the situation. 

If your usual go to with problems is avoidance, shutting down and ignoring it, perhaps spend some time in deep thought over the situation. However if you spend all your time dwelling on problems and never seem able to move forward, you might want to consider actively stopping yourself.

Any time one of those thoughts pop into your head, acknowledge it, don’t punish yourself or feel bad for having that thought. But then tell yourself you’re not going to think about it and then actively distract yourself with something else. Focus on something else or literally get up and make a physical change. 

By understanding the evolution of depression, we can embrace the good qualities it can bring and also tackle the negatives. Hopefully through this, you can gain a better understanding of yourself and be better prepared if it comes back again. 

 

References

 

Andrews, P. W., & Thomson Jr, J. A. (2009). The bright side of being blue: depression as an adaptation for analyzing complex problems. Psychological review116(3), 620.

Kennair, L. E. O., Kleppestø, T. H., Larsen, S. M., & Jørgensen, B. E. G. (2017). Depression: is rumination really adaptive?. In The Evolution of Psychopathology (pp. 73-92). Springer, Cham.