That’s a really good question, thanks chelseastyles! We don’t know specifically why we have nightmares – they’re basically just really bad dreams. But we do know a bit more about HOW we get nightmares. For example, if something really bad or scary has happened to you that day, then your brain might try to process it when you’re asleep, and you’ll have a nightmare about it. Also, weirdly, if you sleep in certain positions, you’ll get nightmares. For example, I can absolutely guarantee that if I sleep on my back, I’ll have a nightmare!
If you’re ill, or have a fever, that can make it more likely that you’ll have a nightmare too. Also, some people think that if you eat just before bed, that can make your brain more active, which might cause them. So lots of reasons really!