My article published on pages 12-13:

Bear Markets and Winter Flu Season: Chronobiology of Financial Market Distress

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In this article, I wish to explain the interrelated nature of seasonal patterns of climate and weather, chronobiological cycles (how solar activity effects human behavior) in respect to economic activity, and financial market cycles, in view of recent winter trends of a pandemic, leading to a great recession and even depression in social and economic life.


Chronobiology is the science that studies how our natural hormonal cycles are synchronized in response to changes in solar activity, such as the circadian rhythm of day-night, or even seasonal patterns of sunshine during summer versus cold winter conditions.

In financial markets, bear markets is a term coined to describe periods of significant economic decline caused by distress in financial conditions, similar to the bear in nature going into winter hibernation. Bull markets, on the other hand, depict the nature of a raging bull, filled with testosterone during the summer mating season, and jumping higher with energy. The nature of animal spirits driving financial markets actually originates in our hormones, providing an impetus for social mood trends and the seasonal nature of financial cycles through human history.

History of bear markets

The current bear market of 2020 occurred as a result of the Coronavirus-19 (Covid-19) pandemic engulfing the globe during winter flu season, starting in December of 2019 in China. The pandemic has caused global lockdowns of economic activity, leading to mass unemployment and Depression-like conditions. The financial panic culminated in March 2020, as the Federal Reserve announced unlimited monetary easing, and even the unprecedented step of buying high-yield corporate bonds (junk bonds) in order to “save the economy” from collapse due to the almost complete shutdown of economic activity.

This follows the last Great Recession of 2009, also occurring with a financial collapse of October 2008, leading the Federal Reserve to initiate a quantitative easing program of money printing that led to a recovery after the stock market bottomed in March 2009 during the end of the winter season. This also coincided with H1N1, Swine Flu epidemic of 2009.

If we look further back in history, the Great Depression of 1929 also began with the crash of October 29, and similarly the great crash of October 1987 occurred during autumn, leading the cold winter season.

Origins of seasonal patterns in chronobiology

This historically well-known pattern of great bear markets, starting with a financial crash around the month of October, the autumn transition season between sunshine of the summer months and the cold winter, is rooted in our hormonal cycles transitioning from raging bull mode during the summer season into hibernating bear during winter.

After winter usually comes the rally in springtime, as the sun begins the shine again in the northern hemisphere during March and April. The bear market of 2009 bottomed out in March, and the current financial panic of 2020 has also diminished since March as stock markets are recovering into May. After the crash of October 1929, stock markets also bounced back for five months, until April, early spring.

In Wall Street there is also a well-known adage, “Sell in May and go away,” which has been time tested as demonstrating surprisingly highly-significant results. If we examine this saying from a chronobiological perspective it makes absolute sense, as the spring period shows the greatest rise of solar activity after low UV radiation during winter.

Long-term solar cycles and financial trends

Kondratiev waves is a theory introduced by Soviet economist Nikolai Kondratiev in 1925, suggesting a hypothesized cycle-like phenomenon in the modern, world economy ranging in waves of about sixty years Kondratiev identified three phases in the cycle, namely expansion, stagnation, and recession, which are based on seasonal patterns. These waves are also associated with changes in social mood:

The first stage of expansion and growth, the “Spring” stage, encompasses a social shift in which the wealth, accumulation, and innovation that are present in this first period of the cycle create upheavals and displacements in society. The economic changes result in redefining work and the role of participants in society. In the next phase, the “Summer” stagflation, there is a mood of affluence from the previous growth stage that change the attitude towards work in society, creating inefficiencies. After this stage comes the season of deflationary growth, or the plateau period. The popular mood changes during this period as well. It shifts toward stability, normalcy, and isolationism after the policies and economics during unpopular excesses of war. Finally, the “Winter” stage, that of severe depression, includes the integration of previous social shifts and changes into the social fabric of society, supported by the shifts in innovation and technology.[1]

The theory of chronobiology, which I develop in my two books, The Testosterone Hypothesis: How Hormones Regulate the Life Cycles of Civilization, and Sex Wars,[2] provides the framework to understand how Kondratiev waves are driven by solar and hormonal seasonal cycles.

If we observe the chart of sunspots since the 1950s, we can see that solar activity is on a declining trend for the last 70 years, leading to the Great Recession of 2009 and 2020, both right at the bottom of the 11-year solar cycle:[3]


As it seems probable that solar activity is declining into a grand solar minimum over the next few decades, similar to the Dalton minimum in the early 19th century that led to the Napoleonic Wars, we may be at the cusp of long period of winter-like conditions. Furthermore, because winter flu conditions are also a product of low solar radiation during the winter period, when more clouds block UV radiation that is known to kill germs during the summertime, we may face more infectious diseases that cause much disruption to economics activity.

Hence, understanding the interconnected nature of solar cycles, climate, and human chronobiology, may provide us with a guide to better adapt to our natural, social and, economic environment in the future.


[1] “Kondratieff Wave,” CMT Association, last modified April 20, 2020,

[2] Roy is the author of these books:

*Sex Wars: How Hormones Drive Gender, Race, & Culture Conflicts (2018)

*The Testosterone Hypothesis: How Hormones Regulate the Life Cycles of Civilization (2015)


Barzilai, R. (2019). Solar cycles, light, sex hormones and the life cycles of civilization: Toward integrated chronobiology. Science & Philosophy, 7(2). doi: 10.23756/sp.v7i2.483

[3] “Sunspot chart,” Sunspot Index and Long-term Solar Observations (SILSO),