We’ve all been there. Someone in the household has a bad night’s sleep, and everybody else pays for the bad mood and the lack of co-operation.

But does a bad night’s sleep actually make you mean?

US researchers found that people are less willing to help others – including those much worse off than themselves – after failing to get enough sleep.

In fact, the researchers found that a single hour of lost sleep, when experienced by an entire nation, which occurs with the advent of daylight savings, significantly eats into charitable donations.

What’s the evidence?

This was a small but clever study where 24 healthy adult participants reported their willingness to help others in their answers to an ‘altruism questionnaire’.

This was done after a night of normal sleep and then after a night of sleep deprivation, with 79 per cent reporting they felt less likely to help others when they had lost sleep.

Self-reported data isn’t the most reliable on its own.

But these participants had their brain activity assessed using fMRI imaging, which found that a night of sleep deprivation was associated with reduced activity in what’s known as the social cognition brain network, notably the parts of the brain “associated with understanding and empathising with others”.

The researchers also investigated the effect of disrupted sleep on real-world behavioural acts of altruism “at a larger societal level”.

This was a neat move. The researchers found charitable donations in the US dropped by 10 per cent in the weeks following the beginning of daylight savings, “as the whole population lost an hour of sleep”.

Broader implications

When we report on sleep deprivation, it’s usually about how it affects the individual, with poor sleep being linked to leading causes of death such as heart disease, plus conditions such as obesity and diabetes, and the derailment of cognitive functions.

But there is a direct social cost too, with poor sleep being a key factor in workplace and road accidents. Other people get hurt, not just the heavily fatigued.

A 2018 review describes poor sleep as “a public health epidemic that is often unrecognised, under-reported, and that has rather high economic costs”.

How else might insufficient sleep affect society? In the new study, University of California, Berkley researchers investigated how a single incidence of poor sleep might affect a person’s willingness to help others.

Given that the success of humans as a species – ruling the world as we seem to do – was only made possible by our evolving into co-operative animals, any impact on our ability to co-operate has serious implications for our future.

Especially when our near future contains critical threats, such as climate change and probably future pandemics.

The study indicates that altruistic acts, such as drives to help victims of natural disasters or war, can be hampered by even minor reductions in a society’s sleep.

The authors conclude that altruistic acts, such as drives to help victims of natural disasters or war, can be hampered by even minor reductions in a society’s sleep.

Dr Matthew Walker, a corresponding co-author of the new paper, and a professor of neuroscience and psychology at California, Berkeley added: “Helping is a core, fundamental feature of humankind. This new research demonstrates that a lack of sleep degrades the very fabric of human society itself.

“How we operate as a social species – and we are a social species – seems profoundly dependent on how much sleep we are getting.”