So the holidays are over, and suddenly everything feels crap. You’re sluggish, unmotivated, maybe low-key angry. You are not imagining it. 

That drag has a name: “post-holiday blues.”

Mental health groups like the National Alliance on Mental Illness describe the holiday blues as anxiety, stress, or emotional letdown that can show up after a season packed with emotional highs and disruptions to routine. Once the series of reunions, parties, shopping is over, what’s left is real life again. Deadlines, alarms, responsibility. And your brain needs time to catch up.

Now add Monday into the mix. That’s where things get biological.

A 2025 research also found that people who report anxiety specifically on Mondays have significantly higher cortisol (stress hormone) levels, measured through hair samples. What’s astonishing is that this pattern showed up not just in workers, but even in retirees. In other words, Monday stress isn’t just about jobs. It’s actually about how our bodies respond to the weekly reset.

Scientific American reports similar findings. Anxiety on Mondays produces a stronger cortisol response than anxiety on other weekdays, which suggests the shift from rest to structure triggers a real physiological stress reaction .

Sleep makes it worse. After holidays and weekends, people tend to sleep later and wake later. Studies on circadian rhythm disruption show that this “social jet lag” throws off mood regulation and stress systems, making Monday mornings feel especially brutal.

There’s also “anticipatory stress,” or the mental load of what’s coming. The same study shows that simply expecting demands can activate stress pathways before anything actually happens .

So yeah. If going back to work feels awful, this isn’t just in your head.