Why Do Neurotics Exist?

Source: Pexels / Anna Shvets

So, imagine that you are in the dating market and you find someone on your dating app who seems to have some potential. His photos show him as extremely fit and handsome. He is, apparently, a successful pediatrician with a major medical practice in your city. And he reports that he walks dogs at a shelter and volunteers in various other capacities. So far, he sounds like a dream. But as you scroll through his description, you see that he (seemingly very candidly) reports being extremely neurotic and emotionally unstable.

Which way would you swipe? Would you give the handsome neurotic doctor a chance? Or does the neurotic thing just not sit well with you to the point that you go onto the next one?

If you're like a lot of people, you are probably put off by the neurotic element of this person's ad. You can envision stressful interactions, worry, emotional volatility, arguments, dramatic situations, etc. By this time in your life, you may well see the writing on the wall with this guy, as great as he may seem otherwise, and move on.

Why Is Neuroticism a Common Human Trait?

The fact that neuroticism is a common human trait provides an interesting evolutionary puzzle. Research on major personality traits shows that, across a wide array of cultures, people who present as high in neuroticism always show up across populations (see Nettle & Clegg, 2008). Further, research on the heritability of neuroticism shows that this particular trait regularly emerges as having a high heritability element. That is, more so than is the case for most personality traits, neuroticism seems to largely be in our genes. In fact, a relatively recent study found that neuroticism has a heritability estimate of over 50%, suggesting that most of the reason that one is neurotic is embedded in that person's genes. Neuroticism is marked by such difficult features as:

• Emotional Volatility
• Excessive Worry
• Proclivity toward Stress
• Mood Swings

It is little wonder that researchers who have studied the relationship between neuroticism and perceived attractiveness regularly show that a tendency toward neurotic behavior and feelings is generally not perceived as attractive.

Yet, this trait, which is largely embedded in one's genes, seems to come back in spades—generation after generation.

The Puzzle of Neuroticism

So, if neuroticism has a high heritability component, but is found as unattractive in potential mates, an evolutionary behavioral scientist should naturally ask the question as to why this trait continues to be prevalent. Why is neuroticism a common trait across all cultures that have been studied? How is this trait maintained if people are put off by those who show marks of neuroticism and are turned off by such signs? Wouldn't the fact that people are not attracted to those who score high in neuroticism, over time, evolutionarily wipe this trait out?

Balancing Selection and the Bright Side of Neuroticism

As an evolutionist, one will typically see something that remains as species-typical and ask about the evolutionary benefits of said feature. In other words: How might a tendency toward neurotic behavior actually lead to survival and/or reproductive benefits?

The idea of balancing selection (see Nettle & Clegg, 2008) can actually shed extraordinary light on this issue. Balancing selection is basically the idea that, within a population, high levels of some trait are often counteracted by some tradeoffs. And, similarly, low levels of that same trait are often counteracted by evolutionary tradeoffs.

As an example, extraversion seems to have obvious evolutionary benefits (e.g., being well socially connected and attractive to others; Nettle & Clegg, 2008) but it seems to come with costs, as well, such as being more likely to contract potentially deadly viruses such as COVID (see Rolon et al, 2021) largely as a function of being surrounded by a higher number of people on a regular basis.

Neuroticism may be thought of with a similar balancing-selection perspective (see Nettle & Clegg, 2008). A hallmark of neuroticism is worry, which often corresponds to vigilance. Consider the following neurotic thoughts that one might have:

• Did I turn off the stove?
• Should I check in the mirror to see if I have spinach in my teeth on more time?
• Is that a den of snakes near the front steps that my kids walk up and down each day?
• This ham's expiration date is tomorrow. Is it OK to eat?

Neuroticism Essential Reads

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Bumps, Bruises, and Loops: The Path to Neurotic Suffering

When you think about neuroticism this way, you can start to see the survival and potential reproductive benefits of this trait—in spite of how unpleasant it may often be.

The Overly Vigilant Smoke Detector

While the adverse outcomes associated with neuroticism are kind of obvious, the fact that this highly heritable trait seems to show up in populations across time and space suggests that there must be something about it that is evolutionarily adaptive. The costs must, somehow, be counteracted by benefits (like on a teeter-totter; this is why we refer to this concept as balancing selection).

Someone who is highly neurotic may well not be found at the top of one's list of romantic partners. And others may describe such a person as "annoying" and so forth. But at the end of the day, the survival and reproductive-related benefits of neuroticism must at least match the costs of this trait. Otherwise, natural selection would have given this trait a Darwinian funeral long ago.

A primary benefit of neuroticism can be thought of in terms of an overly vigilant smoke detector. In our house, we have a kitchen smoke detector that seems highly strung. It goes off if you are sautéing spinach, cooking macaroni and cheese that drips slightly over the edge of the pan while still in the oven, and, without fail, if you are frying potatoes on the stove.

Bottom Line

Neuroticism provides an evolutionary puzzle. It is relatively unattractive, yet high in genetic heritability. And it is common across the globe. When faced with such a situation, an evolutionist will look toward the potential evolutionary benefits of such a trait.

If we think of neuroticism as, essentially, a human version of an overly vigilant smoke detector, the pieces come into place. Neuroticism may not be all-that attractive. And it may lead to difficult and awkward social interactions. Yet, consistent with the concept of balancing selection, it also may well save someone's life—and from an evolutionary perspective, it is hard to think of a more important outcome.