Why We Get Sick on Holiday, and How to Prevent It
“We do not break down under stress; we break down when we no longer need to hold it together.” Dr Marc Schoen, Assistant Clinical Professor, UCLA Geffen School of Medicine
I worked right up to the wire one Christmas. Everything had to be finished, wrapped up and handed over before the shutdown, and I got it all done. I was fine. Tired, but fine.
Then Christmas Day arrived and I woke up genuinely, properly sick.
I was due back at work on Boxing Day and I could not go. I remember how that looked from the outside. Guy takes Christmas off, guy mysteriously cannot face Boxing Day. I knew exactly what people would be thinking, and there was nothing I could do about it, because I was flat on my back and not faking a thing.
At the time I put it down to bad luck. It was not bad luck. It was a pattern with a name, and once you understand it, you can do something about it.
What is actually going on
The pattern is called the letdown effect, described by psychologist Marc Schoen at UCLA in his 2001 book When Relaxation Is Hazardous to Your Health.
The logic runs like this. While you are under pressure, your body raises its immune response and speeds up inflammation. That is not a malfunction, it is the point. Under threat we need to mobilise, not curl up in a corner, and cortisol and adrenaline hold the whole system at a state of readiness.
Then the pressure comes off. The hormones that were holding the line level out, immunity downshifts, and whatever bug you have been carrying around for a fortnight finally gets its opening.
Your body did not let you down. It held the line for exactly as long as you needed it to, and then it stood down.
It is not only colds
The letdown effect shows up across a range of conditions, and the research is more interesting than you might expect.
- A 2014 study from the Albert Einstein College of Medicine had migraine sufferers keep an electronic diary for three months. Their overall stress levels did not predict attacks. What predicted attacks was a drop in perceived stress from one entry to the next, with the migraine arriving six to 18 hours later. The researchers named it the letdown headache.
- A 2015 Taiwanese study found more emergency department admissions for peptic ulcers on Sundays and public holidays than on ordinary working days.
- Schoen also links the pattern to flare ups of asthma, autoimmune conditions, digestive problems and skin conditions such as eczema and psoriasis.
The holiday version has its own name
In 2002, Ad Vingerhoets and colleagues at Tilburg University published research on what they called leisure sickness: people who reliably get ill during weekends and holidays. In a representative Dutch sample of nearly 1,900 adults, 3.2 percent of both men and women recognised themselves in the description.
The number is not the interesting part. The profile is.
It turned out to have almost nothing to do with what people did on their days off. Lifestyle and leisure activities made no meaningful difference. What separated the sufferers from everyone else was high workload, a high sense of responsibility toward work, a high need for achievement, and difficulty adapting to not working.
Read that list again, because it is not a description of people who are unfit or run down. It is a description of people who are good at their jobs and care a great deal about them.
If you are the one who cannot leave without checking one more thing, who feels vaguely guilty on the first morning of a break, who is still mentally running the job while everyone else is in the water, you are the profile. I was, that Christmas.
The symptoms people reported were fatigue, headaches, muscular aches and nausea, and with holidays specifically, colds and flu.
Let me be straight about the evidence. It is thinner than I would like. No large, rigorous study has followed Vingerhoets, and his relied on people recalling their own history after the fact. The pattern is real enough that most of us recognise ourselves in it immediately, but the precise mechanism remains a well supported hypothesis rather than settled fact. I would rather tell you that than oversell it.
How to prevent it
Schoen’s own advice will make instant sense to anyone who trains: do not stop dead.
He describes it as a cool down period for stress, the same way you cool down after a hard session rather than stepping off the treadmill and straight into the car. The aim is to let the body come down gradually instead of dropping off a cliff.
Here is what that looks like in practice.
1. Do not schedule the crash. Finish work a day or two before the holiday actually starts, rather than going straight from your last meeting to the car. That buffer day is not a wasted day of your break. It is the taper.
2. Front load the admin. Pack, book, print and organise earlier than feels necessary so the final 48 hours are calm rather than frantic. Most of us compress everything into the last two days, which is precisely the window in which we most need to be calm.
3. Protect sleep before, not just during. The standard move is to cut sleep in the last week to clear the decks, then plan to catch up once you are away. That is exactly backwards. Your immune system needs that sleep while it is still holding the line.
4. Keep some load on. Do not go from 100 to zero. A walk, a swim, an easy session in the first few days keeps the system ticking over instead of collapsing. This is the opposite instinct to face planting onto the sun lounger, and it works.
5. Expect the dip. The vulnerable window tends to be the first two or three days. If something turns up then, it is not bad luck and it is not weakness. It is physiology, and it passes.
6. Taper on the way back too. The same principle applies in reverse. Returning to a full workload, or a full training load, in one step is the same cliff edge in the other direction.
If it lands anyway
Sometimes you do everything right and you get sick regardless. What matters then is how you come back.
The temptation, especially for anyone who has worked hard for their fitness, is to treat a week off as a catastrophe and to make up for it the moment the fever breaks. I see this constantly. Someone loses ten days to a virus, walks back into the gym and reaches straight for the numbers they were lifting a fortnight ago, then wonders why they feel wrecked for the next month.
The return to training guidance we all learned during the Covid years still holds. Start light. Rebuild volume gradually across one to three weeks before you go anywhere near your previous numbers. Accept that the first few sessions will feel underwhelming, because feeling underwhelmed for a week is a far better trade than losing another two months.
There is a time for pushing through. It is not while you are sick, and it is not while you are recovering. Those are times for rest, food, and gentle movement. The weights will still be there.
The short version
Getting sick the moment you stop is not a coincidence and it is not a character flaw. It is what happens when a system that has been held at high alert is switched off all at once.
The fix is not to be tougher. It is to come off the pressure gradually, at both ends of the break, and to be as patient on the way back as you were sensible on the way in.
I have not had a Christmas like that one since.