Have you ever had a sneaking suspicion that you’re experiencing a scenario that’s already happened? Then you’ve dealt with déjà vu. The term is (as you may have guessed) French, and the literal translation means “already seen.” But in everyday life, déjà vu refers to the weird feeling you get when you’re in a situation that feels like you’ve already lived it, and are somehow living it again.

Research shows that there’s a direct relation between déjà vu and seizures. Specifically, the phenomenon is linked to temporal lobe epilepsy and has been described in people with a known medical history of the condition.

But plenty of people have experienced déjà vu who don’t have a history of epilepsy or seizures. In healthy people, déjà vu is believed to be caused by a memory mismatch, where a new experience is stored in long-term memory and completely bypasses the short-term memory. In this scenario, you have that weird sensation that you’ve been through an experience before when in reality, it’s just your brain’s memory system having a glitch.

There are also other causes of déjà vu that might have more to do with your daily habits than your medical history. One of the most common causes of déjà vu is being overly distracted. Sleep deprivation is another. If you’re walking through life in a perpetual sleep-deprived haze, you might feel like you’re reliving experiences when in truth, you’re just too exhausted to parse reality from dreams.