Sometimes you can feel exhausted but feel unable to rest because your brain is overstimulated. Throughout the day various neurochemicals and hormones help increase concentration. But if you don’t rest properly these can build up – this is known as sleep pressure – and it is this that can make you feel overtired.

Matt Jones, Professor in Neuroscience at the University of Bristol, and research lead for Bristol Neuroscience spoke to BBC Science Focus about how being overtired can ruin your sleep.

“Interestingly, over the same time as sleep pressure builds, the brain can become more and more excitable,” says Matt Jones,

“The neurons in your cerebral cortex [the outer layer of your brain] tend to fire increasingly frequently over the course of an extended period of wakefulness.

"A key theory is that sleep resets your sleep pressure – sleep effectively stops the brain from getting more and more excitable and metaphorically exploding!”

Having thoughts racing through your mind can put you in a state of hyperarousal, making it more difficult to reset your system with sleep.

Matt Jones explained: “Activity in this brain region needs to be slow to enable us to transition into sleep. But during hyperarousal, activity here is abnormally high. And that resists the mechanisms that allow sleep pressure to increase and let us get off to sleep.”

“Rested brains are good at ignoring things that happen all the time but have no real consequence. But if you suffer from insomnia, you’re less able to let go – consciously or unconsciously – of irrelevant information. That accumulates a massive burden on the brain,” he continued.

Read the full feature in BBC Science Focus including science-backed suggestions from Dr Alex Scott, lecturer in psychology at Keele University, on ways you can break the overtiredness cycle and enhance your emotional regulation.