Life

Lack of sleep: why do we feel so emotional when we’re tired?

Does a lack of sleep leave you feeling emotional and short-tempered? Here’s what’s going on inside your brain, according to a sleep expert.

Before we get into this, I’d like to say that I’m usually quite a rational person. I do live with anxiety, but thanks to the time I spent in therapy learning coping methods, I’m usually able to deal with any periods of anxiety relatively quickly.

There’s one situation, however, when all of this goes out the window: when I’ve had a bad night’s sleep. If I go to bed late, struggle to get to sleep or wake up in the middle of the night feeling restless, I know I’m in for a particularly tricky 24 hours the next day.

When I’m super tired I am, quite simply, an anxious, emotional wreck. It’s become such an identifying factor of my personality that if I phone up my Mum and tell her I’m feeling worried about something, the first question she’ll ask me is “how did you sleep last night?”. 

It’s like as soon as I miss out on sleep, all of my emotions become amplified. Instead of feeling anxious, I’m spiralling into panic. Instead of feeling a little annoyed, I’m on the edge of full-blown anger. And instead of feeling a little upset or stressed, I find myself sobbing on the bus. 

A mug on a bedside table
“As soon as I miss out on sleep, all of my emotions become amplified.”

However, I’m not the only one whose ability to handle the world goes out the window when I’m feeling tired. According to research from Bensons For Beds, 87% of British people say tiredness makes them intolerant, with one in five (18%) saying they constantly row with their partner because they feel exhausted. Some 15% of people also said they feel their personality changes when they are tired – and more than a fifth confessed that they swear under their breath at “everything” when they’re lacking on sleep.

With more people struggling with their sleep in lockdown, it’s likely many of us are becoming more familiar with the emotional and mental impacts of a bad night’s rest. 

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But why is this? Stylist spoke to sleep expert Dr Sophie Bostock to find out more, including how a lack of sleep has the potential to impact our mental health.

Why do we get so emotional when we’re tired?

We’ve established that everything gets a bit more trying when we’re feeling low on energy – but what’s going on in our brains to make us feel this way?

“To make sense of this, it’s worth thinking back 200,000 years to when the early humans were living out on the savannah,” Dr Bostock says. “In those days, what would have kept us awake? Predators. Storms. Hunger. Threats to survival. And so, our brains have evolved to interpret sleep deprivation as a potentially dangerous situation. The amygdala, which is the part of our brain which switches on the ‘fight or flight’ stress response, therefore gets more sensitive. This means we become much more emotional, and even small problems feel more stressful.”

A woman with tears in her eyes
“The amygdala gets more sensitive. This means we become much more emotional, and even small problems feel more stressful.”

Because our amygdala is more sensitive when we’re feeling tired, and we’re therefore more likely to have our stress response activated, lack of sleep can also have a physical impact on our body. This is because, when the “fight or flight” response is triggered, hormones flood through our body to help us respond to the thing we’ve identified as a “threat”.

“The stress hormones, adrenaline and cortisol, increase our heart rate, blood pressure and blood flow to the muscles,” Dr Bostock says. “Over time, lack of sleep is linked to an increased risk of high blood pressure, heart disease and even early mortality.”

And why do we struggle to keep those emotions under control?

Now we know why a lack of sleep can make us feel more emotionally sensitive – but that doesn’t explain why we’re more likely to respond in a rash and disproportionate way. According to Bensons For Beds’ research, one in four British people notice they overreact about small issues when they’re tired; feeling annoyed and grumpy is one thing, but shouting at a well-meaning colleague? That’s a whole other kettle of fish. So why do we do it? And what does a lack of sleep have to do with this behaviour?

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“In addition to a supercharged amygdala, the sleep-deprived brain has less activity in the areas of the brain which could be less important if you’re running from a predator,” Dr Bostock explains. “These include the areas controlling forward planning, goal-directed behaviour and self-control.

“In other words, we get more emotional, and we have less of a break on those emotions.”

So, how does this lack of sleep affect our mental health?

Feeling emotional every once in a while, due to a lack of sleep, is OK if you’re able to get some much-needed rest to address that imbalance, but what about when a lack of sleep begins to become a recurring presence in our lives?

“In the short term, one of the main effects is an increase in anxiety – which makes sense if you’re under threat,” Dr Bostock says. “All our emotions can be exaggerated, but we most consistently see an increase in negative emotions and a decrease in positive emotions. We have less energy, and less motivation.”

A woman trying to fall asleep
“In the short term, one of the main effects [of a lack of sleep] is an increase in anxiety.”

It’s undeniable that there’s a strong relationship between the amount of sleep we get and our mental health, but it’s also important to remember that the amount of sleep we “need” is different for everyone – and not to get too fixated on the guidance that says seven or eight hours is the be-all-and-end-all.

As Dr Nerina Ramlakhan – a sleep expert and author of The Little Book Of Sleep: The Art Of Natural Sleep – previously told an audience at Stylist’s Restival, it’s important we don’t spend too much time worrying about the amount of sleep we’re getting.

“I recommend that my clients don’t get too fixated,” she said. “A lot of people don’t sleep so well the night before a big event, or on Sunday nights because they think they must get a good night’s sleep. 

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“If we inflexibly believe [that we need a good night’s sleep] to be the case, that stops us sleeping. And when I’ve worked with professional athletes one of the things I say to them is ‘don’t even think about sleep tonight – you’re playing for England tomorrow, forget it’.

“We could have three or four hours of sleep which are far more nourishing than the seven or eight. It’s that depth of sleep.

“Sometimes the things we think about sleep are stopping us sleeping in the first place.”

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This article was originally published on 12 March and has been updated throughout.

Images: Unsplash

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