In this series, we dig into our strange phobias, fixations, and neuroses, and ask ourselves — Is This Normal?

I was staying at a hotel in Delhi recently, anxious about an important meeting I had the next morning. Through the night, I kept waking up; for some reason, my half-asleep brain was stuck in this nightmare loop, where instead of giving me the wake-up call I’d requested, the hotel workers kept trying to break into my room. Illogical as it sounds, this prospect continued to plague my dreams through the night, waking me up every hour or so. This wasn’t an isolated experience, though. Spending the night in a new place — be it a hotel room, a friend’s house, or an entirely foreign country — is something that routinely makes me anxious, causing me to struggle with falling asleep.

Is this normal? Turns out, it is. Not only that, but it has a name, too; it’s called the “first night effect,” and is characterized by “lower sleep efficiency [and] increased wakefulness.”

Our evolutionary history has a part to play here. In the wild, our ancestors were forced to be cautious in unfamiliar environments because it was the only way for them to ensure they saw the night through. So, the heightened vigilance many of us experience — dubbed as the first-night effect now — is a manifestation of our evolutionary predisposition to be alert in new surroundings. Acting as a built-in safety mechanism, the vigilance is meant to increase our chances of detecting and eliminating potential threats.

Interestingly, human beings aren’t the only creatures who experience this. “We’ve known for quite a while that some marine mammals like dolphins and some of the seals as well as many birds can sleep with one half of the brain at a time,” Niels Rattenborg from Max Planck Institute for Ornithology in Seewiesen, Germany, who specializes in avian sleep, told NPR.

But if we’re evolutionarily wired to stay alert the first time we’re going to bed in an unfamiliar setting, shouldn’t all humans experience it? Yet, most of us have met people who don’t struggle nearly as much, and can pass out pretty much at the drop of a hat — be it at home or in a hotel. Explaining why, Kelly Murray, an adult sleep coach, says, “Its intensity and likelihood varies among individuals based on specific factors — such as current sleep hygiene practices, transitions across time zones, the quality and familiarity of the new sleep environment, and individual personal and medical conditions… Individuals with established sleep routines and healthy sleep habits may experience a milder impact.”

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Moreover, the first night effect isn’t the only reason why one might struggle to fall asleep in new surroundings. Often, changes in one’s regular sleeping environment — in terms of ambient noise, lighting, temperature, the texture of the bedding, or even the softness of pillows — can affect their sleep. Until they’re able to gradually acclimitize themselves to the features of the new setting, at least. But just like it might be challenging to fall asleep in a noisy room next to busy street if one is used to sleeping in peace and quiet, suddenly finding oneself in a communal sleeping arrangement — as it happens with family weddings, camping trips, or occasions when there’s a space crunch — can also make sleep elusive, especially if one isn’t accustomed to sharing their bed.

Being autistic can compound these challenges due to the “need to adhere to a strict schedule or routine in a familiar setting or environment,” suggests News Medical.

Also, as humans, we’re creatures of habit, at the end of the day. As Muhammad Najjar, a neurology specialist in sleep medicine, had told CNN, “There can be a lot more anxiety around sleeping away from home, and that can make it more difficult to sleep.”

Further, since we can rarely teleport our way into new places, more often than not, finding ourselves in a new setting at night is preceded by travel — or, in some cases, moving houses. Besides mental exhaustion, both activities can cause pain due to physical exertion, too. And for some people, it’s the pain signals keeping them up.

Evidently, then, there is a multitude of reasons why falling asleep in new places is challenging. And while one probably can’t do much about it, they can rest assured in the fact that it’s, after all, our brain’s way of keeping us safe.