Blue Monday

These lines are being written during the third week of the year — a time often associated with a phenomenon that began as a marketing campaign and evolved into a media staple: “Blue Monday.” Allegedly the day when spirits are at their lowest, Blue Monday is a concept worth examining through the lens of Behavioral Science to understand why a campaign designed to sell holidays captured the public imagination so effectively.

The term was coined in 2005 by Cliff Arnall, then a tutor at Cardiff University, as part of a collaboration with a travel agency. The goal was simple: identify the exact moment people felt most “blue” and market sunny vacations as the ultimate cure. To determine this date, Arnall created a mathematical formula based on seasonal variables:

Arnall’s Equation

Using these metrics, it was determined that the third Monday of January was the saddest time of the year.

It is important to clarify that because the media adopted this concept so readily, it eventually drew the attention of the scientific community. Mental health researchers have since debunked the formula, concluding there is no evidence to support the idea that any specific day is objectively more depressing than others. However, the question remains: if the science is flawed, why does the concept still feel so relevant?

While cataloged as pseudoscience, Arnall’s factors do align with real influences on behavior, particularly in the Northern Hemisphere.

1. Seasonal Factors: In January, colder weather and shorter days can contribute to Seasonal Affective Disorder (SAD).
2. The Post-Holiday Slump: The end-of-year holidays create high expectations and heavy spending — classic examples of Present Bias and Hyperbolic Discounting. Once the festivities end, people face a sharp Contrast Effect as they return to daily routines.
3. Financial Strain: Many employees receive their December paycheck early, making the gap between paydays feel much longer. This triggers Loss Aversion and complicates Mental Accounting as holiday debts come due.
4. Social Reinforcement: As New Year’s resolutions begin to fade, a sense of failure sets in. This low emotional point is further reinforced by the media through Anchoring Bias (setting the expectation that you should feel sad) and Social Norms.

Awareness is the first step in diminishing the effects of external behavioral triggers. Rather than succumbing to the “Blue Monday” narrative, we can treat this period as a Fresh Start to build momentum.

Get Mario Servin Espinosa’s stories in your inbox

Join Medium for free to get updates from this writer.

Remember me for faster sign in

Practical strategies include:

• Choice Architecture: Rearrange your environment to align with your goals.
• Nudges: Keep your gym clothes in plain sight or place healthy snacks at eye level in the fridge.
• Micro-rewards: Schedule a small treat, like a favorite coffee on Monday mornings, to create a “win” and boost your spirits through positive reinforcement.

References

• Arnall, C. (2005). Blue Monday Press Release. Sky Travel.
• Burnett, D. (2012). Blue Monday: A Nightmarish Mess of Bad Statistics. The Guardian.
• Thaler, R. H., & Sunstein, C. R. (2008). Nudge: Improving Decisions About Health, Wealth, and Happiness. Yale University Press.
• Tversky, A., & Kahneman, D. (1974). Judgment under Uncertainty: Heuristics and Biases. Science, 185(4157), 1124–1131.
• Ariely, D. (2008). Predictably Irrational: The Hidden Forces That Shape Our Decisions. HarperCollins.