Why do I always feel so rubbish after a nap?

Feel great after some daytime zzzs or left feeling groggy? Let Science Focus explain why.

Sleep scientists have found lots of benefits for naps. Napping can help to reduce stress, boost the immune system and improve our mood. Post-lunch naps can help us to stay alert and improve our performance at work, and there’s even evidence, albeit from small studies, supporting the ‘nappuccino’, where people drink coffee just before a nap – and reportedly wake up feeling recharged from the combination of caffeine and sleep.

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Despite all this, naps are not for everyone. Many people wake up feeling groggy. This state is known as ‘sleep inertia’, and it’s more likely to happen when we nap for longer than 20 minutes. It’s not known exactly what causes sleep inertia, but it may involve a molecule called adenosine, which builds up in our brain during waking hours, and decreases during sleep.

Grogginess may result if the adenosine hasn’t fully cleared by the time we wake up. But even short naps have the potential to cause this state (one reason why we should always give ourselves time to fully wake up before, for example, driving). Napping can make us less sleepy at night, so it’s not recommended if you have insomnia.

Genetics appears to play a role in how long infants nap for, so our genes might help to explain why some people feel good after a nap, while others don’t. If napping isn’t for you, don’t feel pressured, but instead work on getting a good night’s sleep!

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