1. Daylight disappears faster than we expect: By December, mornings start in the dark and evenings close early. That lack of light quietly interferes with the body clock, which can make stress hormones hang around longer than usual. You might not feel anxious, just more easily drained.

2. Sleep looks fine on paper, but feels different: You may still be getting roughly the same number of hours, yet winter sleep often feels lighter and less restorative. When rest isn’t doing its job, cortisol tends to stay higher, leaving the body slightly on alert.

3. There’s a lot going on, even when nothing feels dramatic: Work deadlines, money worries, social plans and travel all land around the same time. None of it has to be extreme to feel heavy. The brain stays busy, and stress hormones follow.

4. The body has fewer chances to let tension go: Cold weather nudges people indoors and towards sitting more. Movement is one of the easiest ways to bring cortisol down, and when it drops out of the day, stress can linger in the background.

5. December comes with quiet expectations: There’s an unspoken pressure to feel cheerful, organised or reflective as the year closes. When the mood doesn’t match the season, that mismatch can add strain without announcing itself.