Why does everything feel worse when I’m tired?
· Source: Yoo, Gujar, Hu, Jolesz & Walker, Current Biology, 2007
The baby was up four times, or the flight landed after midnight, or your thoughts simply wouldn’t settle. Now it’s the next evening. A friend cancels dinner with a short message, and it lands like a slammed door. The dishwasher beeps and you want to throw something at it. Even the weather seems to be against you.
On a rested day, none of this would leave a mark. Tonight it all feels personal, and part of you suspects the problem isn’t the message or the dishwasher at all. That suspicion is worth taking seriously, because researchers have looked at what a lost night does to the way we react.
One night awake, then a brain scan
In 2007, Yoo, Walker and their colleagues took 26 healthy young people, aged 18 to 30, and split them into two groups. Fourteen of them stayed awake through a day, the night and the following day, about 35 hours in total. The other 12 slept normally at home.
At five in the afternoon, everyone lay in a scanner and looked at 100 pictures. Some were neutral. Others were more and more unpleasant. The team measured activity in the amygdala. It’s an almond-sized region deep in the brain, and it responds strongly to threats and bad news.
What changed after the lost night
In the sleepless group, the amygdala reacted about 60% more strongly to the upsetting pictures than in the group that had slept. A larger part of it switched on, too: the activated area was three times bigger.
The connections changed as well. In people who had slept, the amygdala was more closely linked to the medial prefrontal cortex, a region at the front of the brain that helps keep emotional reactions in proportion. In the sleepless group that link was weaker, and the amygdala was more in step with brainstem areas that speed the body up.
The authors were careful about what this means. They described their own conclusions about mood as speculative, and this was one small study. Still, the picture is easy to recognise: after a night without sleep, the part of the brain that sounds the alarm was louder, and the part that usually calms it was less connected.
Not everything, mostly the hard parts
The title of this article says “everything”, and the study suggests a correction. When the researchers compared the most neutral pictures, the two groups reacted about the same. The difference showed up with the unpleasant ones.
Minkel, Dinges and their colleagues found something similar from another angle. In two experiments with 53 healthy adults, they kept some people awake for a night and then gave everyone tasks under mild or heavy pressure. After the mild version, sleepless people reported more stress, anxiety and anger than rested ones. Under heavy pressure, both groups were upset about equally.
Put the two studies together, and tiredness doesn’t seem to turn a good evening into a bad one by itself. Calm moments stay mostly calm. Small annoyances, though, start to land like big ones, and that’s exactly the cancelled dinner and the beeping dishwasher.
A full night is not a short night
It’s worth being honest about what was tested. Both studies kept people awake for an entire night in a lab, and the volunteers were young and healthy. Neither looked at the more common case: six hours instead of eight, or a week of restless nights.
It seems reasonable to guess that a short night works like a milder version of the same thing, but that is our guess, not a result from these papers. What they do show is the direction. With less sleep, unpleasant things get a stronger reaction, and the brain’s usual brake on that reaction is weaker.
Tired thoughts are not final verdicts
This is useful knowledge on a bad evening. If the brain is reacting more strongly than usual, then the strength of a feeling tonight says less than usual about how big the problem is. The cancelled dinner may still be a real disappointment. It just isn’t the measure of your friendship.
So one practical move, which is our suggestion and not something these studies tested, is to put off big conclusions until you’ve slept. Decisions about a relationship, a job or your worth as a person can wait a day. Tonight’s job is smaller: notice that you’re tired, and treat your reactions as partly a report on your sleep.
Naming what you feel may help a little, too. In a separate brain-scan study, Lieberman and colleagues found that when people labelled an emotion with a word, the amygdala responded less to unpleasant images than when they sorted the same images another way. That experiment didn’t involve sleep loss at all. It does point to something you can do in the moment besides waiting.
The same evening, a second time
Here is an invented evening, to show how this can go. Priya slept badly for two nights because of a cough in the house. On Thursday her friend texts that she can’t make dinner, and Priya’s first thought is that nobody ever makes time for her.
She notices the size of that thought. So she says it out loud in the kitchen, plainly: “I’m angry that Mia cancelled. I’ve slept about four hours two nights in a row.” Then she asks whether the cancellation would feel this heavy after a good night. Probably not. It would be a small letdown and a new date.
Replying to Mia can wait. Priya writes “let’s find another day” the next morning, after eight hours of sleep, and it reads exactly the way she meant it.
A feeling at the end of a sleepless day is loud. It isn’t always right.
When tiredness isn’t just one bad night
One rough night is ordinary. But if you sleep badly most nights for weeks, if you wake up tired no matter how long you were in bed, or if your mood stays low even after a few good nights, it’s time to talk to a doctor. Sleep problems and long stretches of low mood are both worth taking to a professional, and they often show up together. A diary can’t treat either one. It can give the doctor a clear picture of how your nights and days have actually gone.
Try it tonight
- Before you judge the day, say in one sentence how you slept last night.
- Name the moment that stung most, and ask if it would sting this much after a good night.
- If it can wait, give it a time tomorrow, after you’ve slept.
Say the tired thoughts in Halflight before bed. It keeps them under today’s date, so after a good night you can read them back and see which ones still matter.