Why You Crash the Moment You Slow Down

I will own up to my tell. When the diary fills up, my coffee intake climbs with it. It gets me through the busy days, and for a long time I have been fairly relaxed about that.

The other thing I have picked up on is that when I sit at my computer it is all too easy to close my eyes and drift off for a moment. That tells me more is going on.

In July I wrote about why we get sick on holiday. This post is the other side of the same coin: the crash in energy, mood and focus that can land the moment the pressure lifts, even when you do not get sick. Same pattern, different symptom, and the fix is something you can start this week.

What is actually going on

Your body is very good at rising to a challenge. Under sustained pressure, stress hormones such as cortisol and adrenaline hold you at a state of readiness. Then the pressure lifts and the whole system has to come back down. For some of us, that is where the trouble starts.

I covered the illness side of this in my July post, so here is the short version of the research.

• A 2014 diary study of people with migraine found that overall stress levels did not predict attacks. A drop in stress did, raising the odds of a migraine 1.5 to 1.9 times over the next 6 to 18 hours. It was small, with just 17 people completing the diaries, but it matches what many of us see.
• In 2002, researchers at Tilburg University found that about 3 percent of a representative Dutch sample recognised themselves as getting ill on weekends or holidays. The most common symptoms were headache, fatigue, muscle pain and nausea. Among people describing weekend sickness, about 45 percent of women and 20 percent of men reported fatigue.
• Lifestyle on days off made little difference. What set sufferers apart was a heavy workload, a strong sense of responsibility and difficulty switching off.

Let me be straight about the evidence. Both studies are small, and the leisure sickness work relies on people describing their own history. It is a well supported pattern, not a settled mechanism.

Your energy runs on a rhythm

Cortisol is not the villain. It is part of how you wake up. In a healthy pattern it climbs sharply over the first 30 to 45 minutes after waking, then falls steadily through the day and bottoms out at night. That rise and fall is a big part of why you feel switched on in the morning and ready for sleep at night.

Chronic stress can flatten that curve. A 2017 review of 80 studies found that flatter daily cortisol slopes were linked with poorer health in 10 of 12 outcome types, most strongly for immune and inflammation measures. The link was modest, and it is observational, so it shows association rather than cause.

Bedtime levels seem to matter too. In the Whitehall II study of 4,047 British civil servants, higher bedtime cortisol was linked with roughly double the risk of cardiovascular death for each standard deviation increase, over an average of just over six years. Morning cortisol showed no link. There were only 32 cardiovascular deaths, so treat it as a signal, not a verdict. In that study, the problem was not too little cortisol in the morning. It was cortisol that failed to come down at night.

You may have heard this called adrenal fatigue. The name is the problem. A 2016 systematic review of 58 studies concluded there is no good evidence for it as a medical condition, and your adrenal glands are not burning out. What does have research behind it is a different idea: that in some chronically stressed people the stress system (the HPA axis) shifts, and cortisol output falls. A large 2000 review described low cortisol in some chronically stressed but otherwise healthy people, though the mechanisms remain speculative.

So here is where I land. The tiredness is real, the label is unhelpful, and the science on the cause is unfinished.

Where the coffee comes in

Caffeine is not the enemy. But it matters here for three reasons.

It talks to the same stress system. In a trial of 96 adults, caffeine raised cortisol. Daily intake blunted that response but did not remove it.

It can steal your sleep without telling you. In a small study of 12 healthy sleepers, 400 mg of caffeine (roughly two to three cups of coffee) taken six hours before bed cut measured sleep by more than an hour, and the participants did not notice. Short sleep then has its own effect on your rhythm. After two nights of four hours in bed, 13 healthy men had a cortisol decline across the day that was 21 percent smaller.

It can cause a crash of its own. Caffeine withdrawal typically starts 12 to 24 hours after your last dose, peaks at 20 to 51 hours and can last two to nine days. Headache and fatigue are the standouts, and symptoms have been seen after stopping doses as low as 100 mg a day. If you run on coffee all week and then have a quiet Saturday, some of that headache may simply be the caffeine leaving.

I cannot tell you coffee causes your crash. One finding from the leisure sickness research points the other way: caffeine was the only lifestyle factor that differed between sufferers and controls, and the sufferers reported drinking more coffee on weekends, not less. What I can say is that coffee can muddy the picture, and it is worth being deliberate with it.

How to land it softly

Here is what I would do, in roughly this order. None of it is complicated, and all of it works better done daily than saved up for the weekend.

1. Taper, do not stop dead. Finish a day or two before a break rather than going straight from your last meeting to the sun lounger. After a big project wraps up, give the following days a lighter load rather than an empty diary. In the leisure sickness data, more than half of the vacation sickness cases (56.6 percent) began in the first week, so expect the dip early and plan around it.
2. Downshift every day, not just on the weekend. Try five minutes of cyclic sighing: two short breaths in through the nose, then one long, slow breath out through the mouth. In a month long randomised trial, five minutes a day improved mood more than the same time spent on mindfulness meditation. Meditation still has a place, but a 2021 meta analysis found its cortisol benefit was clearest in people who were unwell, and small and not significant in studies using saliva samples. I would use it for how it makes you feel, not as a cortisol fix.
3. Get outside for 20 to 30 minutes. In an eight week study of 36 city dwellers, a nature break of 20 to 30 minutes, sitting or walking, gave the biggest cortisol drop for the time spent. It fell about 21 percent per hour on top of the normal daytime decline. Participants were asked to leave their phones alone, so I would too.
4. Protect your sleep, especially while the push is still on. Two nights of four hours in bed was enough to flatten the daily cortisol decline in healthy men. Cutting sleep to clear the decks and planning to catch up later is exactly backwards.
5. Set a coffee cut off. Keep your last coffee at least six hours before bed. If you want to cut back, do it gradually by swapping one cup for half strength or decaf, rather than going cold on the first day of a break. Gradual substitution is the approach used in caffeine research to avoid withdrawal symptoms.
6. Eat regularly and drink enough. When blood sugar falls, your body starts releasing adrenaline well before you feel shaky. In a 1987 experiment on 10 healthy volunteers with their blood sugar lowered under controlled conditions, adrenaline release began at about 3.8 mmol/L, while symptoms did not appear until about 2.9 mmol/L. Skipping meals to push through is a stress in its own right. On fluids, a 2025 study of 32 adults found that people who habitually drank about 1.3 litres a day had a cortisol response to a lab stressor more than 50 percent bigger than those drinking about 4.4 litres. It was small and short term, so I would not chase a number. Drink regularly through the day and aim for pale urine.
7. Keep moving, gently. A 2023 analysis found that more active people tended to have a steeper, healthier cortisol decline across the day, although the effect was small. Do not go from 100 to nothing. A walk, an easy swim or a light session keeps things ticking over, and the same logic applies on the way back: rebuild your training load over a week or two, not in one session.

A word on supplements

Rhodiola and ashwagandha get plenty of airtime for stress and energy. Here is what the trials show.

• Rhodiola: In a 2009 trial of 60 adults with stress related fatigue, four weeks of a standardised extract improved burnout scores and attention more than placebo. Both groups improved, which tells you how strong the placebo effect is. A separate review of the early rhodiola studies called the overall evidence insufficient.
• Ashwagandha: A 2025 meta analysis of seven trials (488 people, all in India) found it lowered cortisol but had no significant effect on perceived stress. The lab number moved, but how people felt did not necessarily follow. The trials were short, and rare cases of liver injury have been reported.

If you are curious, speak to your GP or pharmacist first, especially if you have a liver condition, take medication or are pregnant. And remember what supplements cannot do. They do not fix the pace, the sleep or the blood sugar swings that set the pattern off in the first place.

When to see your GP

A dip in energy in the first few days after a big push is common. If it drags on for weeks, or you have severe or new headaches, low mood that will not lift, unexplained weight changes or sleep that stays poor, start with your GP. I would start there rather than with a private saliva cortisol test. The 2016 adrenal fatigue review noted that the cortisol testing methods used in this area are not endorsed by endocrinologists. If spreadout through a single day, x4 ideally, they can give an insight into the patterns though, as opposed to a single test.

The short version

Crashing when you slow down is not a character flaw. It is what can happen when a system held on high alert is switched off all at once.

The fix is not to be tougher. Come down gradually, protect sleep, food, water and movement every day, be deliberate with the coffee, and be patient with the first few days.

Is coaching right for me?

If you lead a team that runs hot, my corporate programme builds these habits into the working week.

References

This post was sparked by Dr Robin Berzin’s article, Why You Crash When You Finally Slow Down. I checked the research behind it and added my own take.

1. Cadegiani and Kater (2016). Adrenal fatigue does not exist: a systematic review. BMC Endocrine Disorders.
2. Heim, Ehlert and Hellhammer (2000). The potential role of hypocortisolism in the pathophysiology of stress related bodily disorders. Psychoneuroendocrinology.
3. Stalder et al. (2016). Assessment of the cortisol awakening response: expert consensus guidelines. Psychoneuroendocrinology.
4. Adam et al. (2017). Diurnal cortisol slopes and mental and physical health outcomes. Psychoneuroendocrinology.
5. Kumari et al. (2011). Association of diurnal patterns in salivary cortisol with all cause and cardiovascular mortality: Whitehall II. Journal of Clinical Endocrinology and Metabolism.
6. Vingerhoets, van Huijgevoort and van Heck (2002). Leisure sickness: a pilot study on its prevalence, phenomenology, and background. Psychotherapy and Psychosomatics.
7. Lipton et al. (2014). Reduction in perceived stress as a migraine trigger: testing the let down headache hypothesis. Neurology.
8. Lovallo et al. (2005). Caffeine stimulation of cortisol secretion across the waking hours in relation to caffeine intake levels. Psychosomatic Medicine.
9. Drake et al. (2013). Caffeine effects on sleep taken 0, 3, or 6 hours before going to bed. Journal of Clinical Sleep Medicine.
10. Juliano and Griffiths (2004). A critical review of caffeine withdrawal. Psychopharmacology.
11. Guyon et al. (2014). Adverse effects of two nights of sleep restriction on the hypothalamic pituitary adrenal axis in healthy men. Journal of Clinical Endocrinology and Metabolism.
12. Balban et al. (2023). Brief structured respiration practices enhance mood and reduce physiological arousal. Cell Reports Medicine.
13. Koncz, Demetrovics and Takacs (2021). Meditation interventions efficiently reduce cortisol levels of at risk samples: a meta analysis. Health Psychology Review.
14. Hunter, Gillespie and Chen (2019). Urban nature experiences reduce stress in the context of daily life based on salivary biomarkers. Frontiers in Psychology.
15. Schwartz et al. (1987). Glycemic thresholds for activation of glucose counterregulatory systems are higher than the threshold for symptoms. Journal of Clinical Investigation.
16. Kashi et al. (2025). Habitual fluid intake and hydration status influence cortisol reactivity to acute psychosocial stress. Journal of Applied Physiology.
17. Moyers and Hagger (2023). Physical activity and cortisol regulation: a meta analysis. Biological Psychology.
18. Olsson, von Schele and Panossian (2009). A randomised, double blind, placebo controlled, parallel group study of the standardised extract SHR 5 of the roots of Rhodiola rosea in the treatment of subjects with stress related fatigue. Planta Medica.
19. Blomkvist, Taube and Larhammar (2009). Perspective on roseroot (Rhodiola rosea) studies. Planta Medica.
20. Albalawi (2025). Dual impact of ashwagandha: significant cortisol reduction but no effects on perceived stress, a systematic review and meta analysis. Nutrition and Health.