Depression
What is it and what is it for?
Depressive disorders are among the most common mental health issues. In 2021 it was estimated that 4% of people worldwide experienced depression during that year.
In spite of its prevalence, depression is still not well understood. It is still not clear why people get depressed or how to end depression. People who are depressed often feel as if they are in the dark without an idea of where the exit door is. Treatments exist, but their efficacy can vary from person to person and the reasons are somewhat unclear.
I have argued that our happy and unhappy feelings are designed to help us make good decisions. However, this perspective does not seem very useful in explaining depression, which is typically characterised by pessimism, a lack of motivation to engage with the outside world, and a reluctance to take action. How can this be helpful in making decisions?
Why we experience bad moods
To understand depression we need to understand moods. Moods are lasting positive or negative feelings. At first sight, moods do not seem to be very helpful in improving our decisions. We may feel cheerful or unhappy all day, with these feelings spanning a wide range of different decisions. Is there a reason we experience moods?
One way to understand the role of mood is that we don’t just make decisions about things we enjoy or dislike in the moment. We also make choices that influence our circumstances over time, like choosing a job, or a romantic partner. Moods can be explained as signals for the value of the situations we are in. These feelings nudge us to try to change the situation when it is bad and to stay in it when it is good. This idea has been developed by Randolph Nesse in his book Good Reasons for Bad Feelings (2019). He points out that what makes situations good or bad are the opportunities (upsides) and risks (downsides) that characterise them.
High and low moods were shaped to cope with propitious and unpropitious situations. […] Individuals whose mood rises in propitious situations can take full advantage of opportunities. Individuals whose mood goes down in unpropitious situations can avoid risks and wasted effort and can shift to different strategies or different goals. - Nesse (2019)
From this perspective, long episodes of depression can arise when we get stuck in an unpropitious situation.1
Sometimes, … the goal is something the person cannot give up, such as finding a job or a partner or a cure for a fatal condition. In such a situation, people can get trapped pursuing an unreachable goal, and ordinary low mood escalates into severe depression.2 - Nesse (2019)
This explanation of the role of moods does not mean that severe depression is adaptive, that it has a function.3 Psychologist Daniel Nettle (2004) made a compelling case that while temporary depressive mood can be adaptive, long episodes of depression are likely not. He points out that depression does not have the characteristics of an adaptive trait: it is heritable; it does not only appear in unpropitious situations; it does not seem to help people move away from an unpropitious situation when they are stuck in one; and people who don’t experience it don’t seem to be disadvantaged.
Instead of thinking of depression as adaptive, Nettle makes an interesting suggestion. For every psychological trait, there are individual variations in a population. How our mood system helps us navigate different propitious and unpropitious situations may be a trait that is also distributed in the population. As a consequence, some people may be more prone to low moods, while others may be more prone to high moods.
A psychological dimension related to this might be neuroticism. People with low neuroticism tend to feel fine in most situations. On the contrary, people with high neuroticism tend to be more negative and worried.
A possible explanation of how depression works
I’ll present a new argument here.4 Our subjective satisfaction arises from the comparison of what we have to a reference point. A given level of achievement can feel great with a low reference point and terrible with a high one. The figure below shows how subjective satisfaction changes as a function of the reference point (each curve’s reference point is its midpoint).
It is possible that variations in neuroticism induce variations in the propensity to have a high or low reference point. The propensity to experience lasting depression could therefore stem from having unusually high reference points when judging one’s situation.
This may seem paradoxical. How could depression be associated with higher aspirations when it seems to be associated with a lack of motivation to do anything? The answer lies in the fact that having a point of reference that is too high is demotivating, as the options we face all feel pointless. In support of this explanation, depressed people often express what seems to be frustration with what they experience relative to what they think they should or could experience instead: they feel that they have “failed”, or that they “deserve better”.5
From this perspective, depression is the consequence of an extreme variation of a mood system designed to help us in our choice of situations. It is a disorder, but one we can expect, as any system designed by evolution will feature some variations.6 Stoicism is famous for recommending that we learn not to care about bad things we cannot change. Severe depression may arise from the opposite tendency: feeling bad about situations that cannot be changed. If this is the case, it makes sense not only to try to improve the circumstances of people who are depressed, but also to help them adopt a more positive outlook.
Depression cripples many during their lifetimes. Its mechanisms and the solutions to escape it are still not fully understood. An adaptive perspective helps us see it through the lens of moods and their functions. From this view, depression appears as a reaction (an overreaction when depression is severe) to a situation experienced as unsatisfactory given our aspirations, without clear solutions to change it.7 Reducing depressive feelings can then follow two paths: helping to improve the circumstances causing the depressive mood, or helping the depressed person come to terms with the circumstances causing the depression if these cannot be changed.
I thank Daniel Nettle for providing me with early comments on these points. This post is part of a series on happiness. In the final posts of this series, I will look at the big questions about the nature of happiness and the implications for the idea that we should maximise happiness in society.
References
Hagen, E.H., 2002. Depression as bargaining: The case postpartum. Evolution and Human Behavior, 23(5), pp.323-336.
Nesse, R.M., 2019. Good reasons for bad feelings: Insights from the frontier of evolutionary psychiatry. Penguin.
Nettle, D., 2004. Evolutionary origins of depression: a review and reformulation. Journal of Affective Disorders, 81(2), pp.91-102.
Nettle, D. and Bateson, M., 2012. The evolutionary origins of mood and its disorders. Current Biology, 22(17), pp.R712-R721.
Tamir, M., 2005. Don't worry, be happy? Neuroticism, trait-consistent affect regulation, and performance. Journal of Personality and Social Psychology, 89(3), p.449.
The following figure shows how potential upsides and downsides in a situation can be reflected in different moods. It is inspired by Figure 1 in Nettle and Bateson, though I changed the axes, in the spirit of Nesse (2019)’s description of moods’ functions.
The full quote is worth reading:
When people are making progress toward their main life goals, they feel fine. Obstacles provoke frustration, often observed as anger and aggression. Inability to make progress toward a goal causes demoralization and temporary withdrawal. Prolonged failure of a strategy leads to more severe demoralization and attempts to find alternatives. When extended efforts fail to find a new route to the goal, intense low mood disengages motivation from the goal. When the unreachable goal is truly given up, low mood is replaced by temporary sadness aroused by the loss, and the person moves on to pursue other more reachable goals. Sometimes, however, the goal is something the person cannot give up, such as finding a job or a partner or a cure for a fatal condition. In such a situation, people can get trapped pursuing an unreachable goal, and ordinary low mood escalates into severe depression. - Nesse (2019)
There have been suggestions that this may, for instance, lead people to adopt a more submissive attitude toward a dominant other. This seems to be a very specific explanation, given the wide range of situations in which depression could occur and the wide range of consequences it has on behaviour. Can’t something other than depression do the trick? It seems like breaking a nut with a sledgehammer. Another explanation sees depression as a social signal to gain support from others (Hagen, 1999). This explanation is relevant for specific types of depression.
This argument is currently being studied by neuroeconomist Paul Glimcher, who examines the neural correlates of reference point location and its relation to depressive states.
The possibility that neuroticism is associated with a higher reference point is also compatible with the observation that people with higher neuroticism seem to act as if they have a higher reference point, with greater motivation to improve their circumstances.
individuals high in neuroticism may be more engaged in effortful performance when worried (Tamir, 2005)
This makes sense because our motivation initially increases when our reference point is slightly above what we have (we want to reach this reference point). It is when our reference point is out of reach that it becomes demotivating.
It is also possible that modern environments interact with our mood system in ways that are more likely to generate depression.
It's interesting that all that presents depression as FUNDAMENTALLY, at least on some level, reactive, or at least inter-active with the environment, rather than focusing on "fairly random disruption in neurochemistry that MIGHT "have a reason" but often doesn't" -- which is a narrative that seems to dominate current mainstream framing of depression.
It all goes back to your thesis on the reference point / expectations and the tension between coasting (low expectations leading to a "wasted" life by some account and probably leading to boredom and depression) and pushing too hard (unrealistic expectations leading to stress and depression). I think you adjudicate this tension by saying that we are evolutionarily built to push too hard and change the goal post b/c this is how we have the most success. And furthermore we cannot help but be unhappy in the service of achieving our potential. Depression as deep unhappiness would be the logical consequence of that process on one tail of the population distribution?
While this normative description makes sense to me, I propose that this tension is solved differently - which is by developing and cultivating a value system that brings joy in ones life because it is meaningful intrinsically not because it leads to external validation/accomplishments. The Stoics whom you quote have a lot of useful stuff to say about this - control, virtues, impermanence etc.
I am curious to know how many people educated in the main Stoic teachings consider themselves depressed. And how many people that had been depressed came out of it or have reduced symptoms after they read the Stoics. I assume that all the true religious (even the socially religious) would score well given the meaning they get from their practice, community etc. In other words, I am curious to know if deep depression (as a biological heritable trait) can be overcome with developing a moral theory of what it is to live a good life .