The Depression Reflex in the Animal Kingdom

If depression is an evolved adaptation to stress, the immediate question is what possible benefit it could bring.

As discussed in the Depression Reflex, it makes evolutionary sense for a creature hit by defeat, loss, or injury to withdraw – a strategic retreat that stops a bad situation from becoming worse. That explains the physiological response of loss of energy, interest and motivation – all of which act to keep the animal temporarily away from danger, or from making rash and premature attempts to restore their fortunes.

The depression reflex is a behavioural shutdown, and the benefits it must have given our most ancient ancestors are easy to discern.

The Human Experience

Unfortunately in humans, the response lodges in consciousness where it is deeply painful and undermines our self-esteem, relationships and hope. In a civilisation where vigorous activity is the central sign of health and currency of success, depression is naturally seen as a disorder.

The Nature of Depressive Thinking

We can see this through subtle changes in language over time. Until very recently, the most common greeting was something along the lines of “How are you? Are you well? And your family?”

In a society where the major threats were disease or injury, an enquiry about health made perfect sense. If the answer came back negative, the questioner could respond by keeping their distance while perhaps offering tangible aid.

Today the standard questions have shifted, and along with it the answer. “How are you going? What have you been up to? Keeping busy?” Hearing that someone has not been busy is a sign of concern. Health has morphed into activity. Busy is the new standard of wellness.

The implication is that depression is the new disease.

Depression’s Impact on Cognitive Function

As we have seen, depression in humans has a novel sphere to invade – consciousness – and once there it can start to cause itself. Whatever evolutionary benefit it once had appears entirely lost. The experience is uniformly painful and comes with intrusive ruminations about various flaws and failures.

We might ascribe the mental anguish to an evolutionary accident, something that was bound to happen when an ancient response was preserved in creatures with a prefrontal cortex. Yet we could also imagine an alternative where depression simply took the form of severe lethargy and sleepiness: here the sufferer would also be forced to withdraw but without all the pain.

Depression would be more like hibernation, self-esteem and optimism could remain intact, and most of all, its penchant for enduring beyond its mandate would be gone. Was it just rotten luck in the lottery of evolution that left us with the cognitive effects too? Or could depression’s painful and involuntary thinking patterns offer some benefit, however obscure? Far from being suppressed like physical activity, depressive thinking often flows in abundance.

The difference is that the thoughts of depression are constrained in rigidly negative channels. Ruminations take hold, where the mind returns again and again to perceived failures, humiliations and defects, some of which others may see as absurdly trivial.

In psychotic depression, rumination falls into frank delusion, where the patient may become utterly convinced that they are guilty of a horrible crime, damned to hell, or even physically dead. While thinking that goes that far is obviously disordered, the question stands whether the early stages of critical self-reflection might be helpful. Several thinkers on the subject are making the claim that it is.

Supporting evidence comes from a variety of studies showing that depressed mood “promotes an analytical processing style that enhances accuracy on complex tasks”.[1]

Other studies have shown that performance on cognitive tests is clearly impaired, and it is well known among psychiatrists that dementia cannot be confidently diagnosed until depression is ruled out. The picture is complicated, with the possibility that some types of thinking are enhanced while others are diminished.

Until recently, almost all psychiatrists assumed that depression simply impaired problem-solving, end of story. That viewpoint comfortably explained why depression usually makes fixing the problems that brought it about more difficult, meaning that patients need external help from medication or therapy to recover. Yet there is the intriguing possibility that all the studies and clinical encounters that led to this conclusion were examples of depression in its more severe form – depression which has taken root in the mind and entered the vicious circle of being its own cause.

Invisible to these researchers may be a briefer, milder level of depressive thinking which never came to their attention because it actually achieved its purpose of helping to find solutions to the problems which caused it. If so, a total reversal to our understanding of depression might well be true.

The Analytical Rumination Hypothesis

A major proponent of this new perspective is Paul W. Andrews, who has introduced the Analytical Rumination Hypothesis.

He believes that depression promotes “an analytical reasoning style in which greater attention is paid to detail and information is processed more slowly, methodically, thoroughly, and in smaller chunks”.

To summarise his main claims:

1. Depression is a stress response triggered by complex problems
2. Physical and cognitive changes promote sustained analysis to generate and evaluate potential solutions
3. Other thinking patterns are downgraded as resources switch to rumination

The depressive thinking summarised above as “rumination” involves enhanced attention combined with priority for problem-related information.

Resources have been shunted away from any avenue of pleasant thought, along with the desire to do anything active. Not only does that heighten focus on the problem, but it reduces exposure to potential distractions. The person experiences this as continually thinking about everything that went wrong, is wrong, and could go wrong.

Creativity and Depression

One side effect is terrible performance on cognitive tests. Partly this comes from diminished motivation for anything which is not “the problem”, and the rest is the cognitive resources being currently elsewhere. Suddenly, one of the paradoxes of depression makes sense: the observation that low mood seems to ruin cognitive performance while also being a font of creativity for artists and writers.

Psychiatrists have assumed that the flurries of creative endeavour often reported during depression (which may be as simple as filling pages in a journal) are really the effect of emerging from depression, not the mood itself. Countless writers and artists have always protested otherwise, insisting that some of their most fruitful periods come from moments of the bleakest despair.

With the AR hypothesis, we can see that perhaps they are right after all.

Depression whisks them away from life’s distractions to zero in on a central problem. They write or paint because they literally cannot think about or do anything else.

Experimental evidence has been found for this perspective through the use of functional MRI. Depressed brains are found to have enhanced connectivity in what is known as the “default mode network”, which regulates internal focus. In these pictures we can actually see the pathways that carry the excessive ruminations of depression, and perhaps sometimes a pearl of creative insight.

When these thinking patterns become too entrenched, rumination has certainly outlasted its welcome and for those patients a follow-up study offers hope.

The study first confirmed the hyperconnectivity in subjects with depression, then they received a five-week course of TMS treatment. When their brains were re-examined under MRI, the patients whose depression improved showed a pattern: the hyperconnectivity was back to normal.

This study offers an intriguing insight for at least one of the mechanisms behind the mood and cognitive benefits of TMS. The study also showed that it was the patients with hyperconnectivity who improved, which suggests that there may be a role for MRI in predicting TMS outcome and thus for targeting the patients most likely to benefit.[2]

The AR hypothesis also meshes perfectly with the evolutionary perspective of the depression reflex, which now allows us to outline the whole story.

A New Understanding of Depression

Someone faces problems which their usual measures cannot solve. The mind registers a sense of feeling trapped or defeated with no clear way out, which sets off the physiological response of depression. Behaviourally, this results in withdrawal from all active pursuits, and cognitively, a relentless focus on what went wrong. Withdrawal stops them from making their problems worse, and the rumination gives them the best chance of solving them.

From this view, depression is much like the body’s programmed response to infection, a fever. By making the person feel listless and miserable, it forces them to stop and rest. By ramping up core temperature, it makes the environment less hospitable to invaders.

Long ago, the body adopted this solution to enhance survival, and since it worked, the response is still with us today. Looking at the withdrawal and rumination aspects of depression, it makes sense that long ago the mind adopted this defence as well.

So far this sounds like an excellent program, but of course that’s not where the story ends. If the enforced lay-off fails to solve the problems that triggered it, depression settles in and becomes yet another problem, perhaps even dwarfing all the others. Depression being far more harmful than helpful is the major argument against the adaptation view.

Part of this may be resolved by seeing that depressive thinking in the early stages may be helpful, and the mood only becomes harmful when it stays too long. In that sense, the writers of the DSM got it right by declaring that depression is only depression once it has stayed for at least two weeks, as well as causing social or occupational dysfunction.

The central question is why depression overstays its welcome.

I discussed this in the previous article, The Depression Reflex, but an understanding of the AR hypothesis can expand the picture. We saw that in the animal kingdom, the triggers that lead to withdrawal are short-lived, so the response rapidly shuts off.

There is also no sphere of consciousness where depression can take root. For early humans, the triggers would have been more complex but still in the realm of the solvable.

A hunter may have been faced with repeated failures to bring down his prey. He retires to his cave, ruminates, and emerges a few days later with an idea for a sharper spear.

In scenarios such as these, depression provided a necessary circuit-breaker, and evolution rewarded it with a permanent place in the genome. The trouble came much later when humans settled into societies that were exponentially more complex, and accordingly, so too were their problems.

The change dates back at least 10,000 years, the briefest instant in evolutionary time.

From recently unearthed clay tablets at least 3000 years old, we hear:

If depression continually falls upon him, he continually sighs, he eats bread and drinks beer but it does not go well for him, then says, ‘Oh, my heart!’ and is dejected, he is sick with lovesickness; it is the same for a man and a woman.

And again:

If a man eats (and) drinks, but it does not approach his flesh, he is sometimes pale, sometimes red, sometimes his face becomes darker and darker, he is worried, he is depressed, his heart is not up to speaking.

Since humans moved from relatively simple tribal life into cities, a single life became a node in a vast network far beyond the capacity of any individual to understand. Suddenly problems were not just immediate and tangible but abstract and elusive.

For millennia thereafter, a strict social order and universal belief systems acted to curtail much complexity, but in the last few centuries and especially the last, society became awash with a dizzying array of worldviews and ways of life.

Freedom and possibility have rushed in as the old certainties have crumbled but whisked away in the deluge are clarity and simplicity, and with them, peace of mind.

An interesting observation that claims to prove this experimentally comes from a study which compared a diner’s satisfaction with the number of dishes on offer in the menu. Diners were overwhelming more satisfied after fewer choices, even though they thought they would be happier with more.[3]

More evidence comes from the sad fate of tribal societies after contact with Western civilisation, where depression and all its problems are rampant. The complexity of modern life is certainly corrosive to happiness, and recently our interconnectivity has launched into an exponential new level with the internet and social media. Now there is no longer a place to withdraw: a screen is always handy and the manifold connections that fuel our discontent never switch off.

And so the problems are both too complex to quickly solve and now encroaching into any period of withdrawal.

Adapting to Modern Complexity

All this means that the depression reflex that aided the survival of early humans has become useless and even harmful in the context of modern life. Our more complex problems require more complex solutions, and fortunately patients can now turn to advances in lifestyle changes, medication, therapy and neurostimulation.

Yet we should also keep in mind the deep, ancient program embedded in our DNA, and harness the experience of withdrawal and rumination to solve what we can on our own.

References

1. From Andrews PW, Thomson JA Jr. The bright side of being blue: depression as an adaptation for analyzing complex problems. Psychol Rev. 2009;116(3):620-654. doi:10.1037/a0016242. Studies cited for this claim: Alloy & Abramson, 1979; Ambady & Gray, 2002; Au, Chan, Wang, & Vertinsky, 2003; Braverman, 2005; Forgas, 1998, 2007; Gasper & Clore, 2002; G. Hertel, Neuhof, Theuer, & Kerr, 2000; Sinclair, 1988; Sinclair & Mark, 1995; Storbeck & Clore, 2005.
2. Magnetic Stimulation May Halt Rumination in Depression, Nessa Bryce, Scientific American, January 1, 2015
3. Johns, Nick & Edwards, John & Hartwell, Heather. (2013). Menu Choice: Satisfaction or Overload?. Journal of Culinary Science & Technology. 11. 10.1080/15428052.2013.798564.