What to expect this week:

Been super busy with my own personal life this past week, and glad to say that it’s a good kind of busy! But I have not had much time to work on Evolve.2, so this week is a shorter one.

Seasonal Affective Disorder is the topic. If you don’t know what that is, your answer lies below. If you do and you think you might suffer from it, that answer lies below as well

Housekeeping:

Links to my e-Courses

• The Bare Minimum - FREE

• The Adaptive Scholar - $5

What is Seasonal Affective Disorder? (and how to cure it) 

Emotions are the product of evolution. Over the course of millions of years, they helped guide adaptive behavior, signaling to us when it might be advantageous to run and hide from a predator or to pursue a mate. They were responses to environmental cues.

Because of their role in motivating certain behaviors in response to the external world, they often emerge due to reasons beyond our self-control. They evolved to be subconsciously produced and reflexive because life-or-death situations can sometimes be a matter of seconds. 

In addition to our evolutionary history, our surroundings, social groups, and environments all influence our emotional state. Seasonal Affective Disorder (SAD) is a prime example of how our environment shapes how we feel, and how that feeling has roots in our evolutionary history.

Put simply, SAD refers to the tendency to feel tired, depressed, and all-around lethargic during the colder, darker months of the year. And, it can be traced back to our Paleolithic past. Studying evolution can help explain why you yearn for summer during the winter months and even inspire innovative ways to treat this disorder.  

Seasonal Affective Disorder Symptoms

SAD was first formally acknowledged in the scientific literature in 1984 by American psychiatrist Norman Rosenthal and colleagues [1]. They define SAD as, “ a condition characterized by recurrent depressive episodes that occur annually.”

In their initial study, they diagnosed 29 people with this condition. Their symptoms consisted of hypersomnia (excessive sleepiness), overeating, depression, and carbohydrate cravings. Importantly, the onset of these symptoms came about in the fall or winter and subsided by the following spring or summer. While the reverse can happen on occasion, whereby symptoms are more present in the spring and summer, fall/winter SAD is far more common. 

Since these initial findings, clinical research has shown that it is a rather common condition [2]. So, now that it has been observed and documented, how can we begin to explain and treat it? The key lies in our past.

Is SAD Adaptive?

For most of human history, equatorial Africa was our home. Then, around 60-70,000 years ago, members of Homo sapiens (our species) built the courage to explore lands unfamiliar. They migrated to places far and wide, from Europe to Asia to Australia (take your wildest guess as to how they made it there). Along with the migration into new continents came new climates and weather patterns. A common trend in these new lands was increased seasonal fluctuation, accompanied by colder, darker winters. This is especially true as they moved further north to greater latitudes.

Being adapted to the warmer, brighter, and more consistent climate of Africa, these migrating populations were relatively unprepared for the onset of winter. Herein lies the evolutionary function of SAD. 

In the animal kingdom, winter is a time for hibernation. Bears stuff their faces, squirrels bury their nuts, and they both settle down for the winter. The earliest humans leaving Africa probably weren’t all that different. As they experienced the food scarcity brought about by winter, maintaining their typical African energy expenditure was unfavorable. If you continued to travel 10 miles per day in this new environment with fewer calories available than normal, you would eventually reach a severe caloric deficit - and in the natural world, this could mean death.

This is the logic behind Caroline Davis and Robert Levitan’s energy conservation theory of SAD [3]. According to them,

Lethargy and food cravings are precisely the energy-conserving traits that would have been adaptive for people trying to survive the winter season. 

They go on to specify their theory even more.

All humans could have benefited from these behaviors, but females in particular would have benefited to an even greater degree. Pregnant women need not only sufficient energy for themselves but for their growing fetuses as well. To maximize the probability of a successful birth, evolution would have favored ancient mothers who had their babies in spring. Before hospitals and artificial heating, a baby born in the winter was a baby born with bad luck. Therefore, mothers are even more incentivized to consume and conserve in the winter.

This can explain, according to Davis and Levitan, why females are more likely to experience SAD. “There is considerable indirect evidence that in temperate climates, the symptoms of SAD reflect a predisposition for conception to occur in late spring/early summer to ensure a peak of births in the late winter/early spring”, they say. 

They note how the symptoms of SAD are so similar to the behavioral changes associated with pregnancy (increased sleep, weight gain, cravings, pronounced emotionality, etc.). “In other words”, they argue, “the symptoms of SAD, which reoccur each autumn and remit each spring, coincide with seasons that were historically optimal for conception, gestation, and lactation, and simply reflect the female body’s natural preparation for the process of childbirth.”

At the end of their paper, Davis and Levitan make an important point with regard to the modern implications of our SAD winters. They note how modern conditions are much different; that we have cultural barriers to winter, like shelter and heating appliances. SAD is, therefore, a “relic of biological preparedness” that is no longer a necessity but remains psychologically relevant. This depressive state likely was, but no longer is, adaptive.

How to Cure Seasonal Affective Disorder

Given this evolutionary logic, what are some practical tools we can implement to treat or even prevent SAD?

One tool to help fend off the winter feels is to quite literally return to your place of origin. Evolutionary biologists Bret Weinstein and Heather Heying suggest you should [4].

Returning to the environmental state in which we evolved, even intermittently, could come with benefits to our mood and emotions.

This is an exciting idea, and one that could be effective for you, but not everyone can afford to travel to the tropics on an annual basis. Luckily, there are more cost-friendly alternatives. 

Increasing the amount of light you’re exposed to throughout the day is one of these alternatives. Light therapy has been shown to effectively treat SAD patients, especially when performed in the morning - making it a “dawn simulation” [5]. In fact, studies show that “2500-lux intensity light exposure for at least 2 hours daily for 1 week resulted in significantly more remissions when administered in the early morning (53%) than in the evening (38%) or at midday (32%).” [6]. This means that increasing morning light is especially important.

The long, dark mornings of higher latitudes are counter to what our species experienced for millions of years, especially when that darkness is extended by people staying in bed to scroll through Instagram instead of going outside to see the sun. By simulating an earlier sunrise with bright light exposure, you are introducing a feature of ancestral environments back into your daily life, which can in turn treat and/or prevent SAD symptoms.

References:

[1] Rosenthal, N., et al. 1984. “A description of the syndrome and preliminary findings with light therapy.” Archives of General Psychiatry 41(1):72-80.

[2] Western, A. and Lam, R. 2007. “Seasonal Affective Disorder: A Clinical Update.” Annals of Clinical Psychiatry 19(4):239-246

[3] Davis, C. and Levitan, R. 2005. “Seasonality and seasonal affective disorder (SAD): an evolutionary viewpoint tied to energy conservation and reproductive cycles.” Journal of Affective Disorders 87(1):3-10.

[4] Heying, H. and Bret Weinstein. 2021. A Hunter-Gatherer’s Guide To The 21st Century: Evolution And The Challenges Of Modern Life. New York, NY: Portfolio.

[5] Golden, R., et al. 2005. “The efficacy of light therapy in the treatment of mood disorders: a review and meta-analysis of the evidence.” American Journal of Psychiatry 162(4):656-62.

[6] Terman, M., et al. 1989. “Light therapy for seasonal affective disorder. A review of efficacy.” Neuropsychopharmacology 2(1):1-22.

Fit Fuel Song Suggestion

The Fit Fuel song suggestions are hand-picked by yours truly to elicit the motivation (and possibly aggression) needed to initiate or persist through a grueling workout. They consist of heavy, brutal guitar riffs and gruesomely guttural vocals. Additionally, I timestamp what I believe to be the best riff of the song - one that will kick your nervous system into overdrive when approaching a personal record (PR).