Whenever Robinson Leoni spends his initial night somewhere new, the pattern remains identical: drifting off takes longer, nighttime awakenings occur far more frequently, and his total rest suffers.

At home, he averages seven hours. Spending an evening elsewhere—regardless of earplugs or mattress quality—drops his smartwatch total to roughly five hours.

“I feel normal, you know, no stress, nothing, but it’s just I notice I wake up continuously,” said Leoni, a sales director for a tech company who travels once or twice a month for work.

He is experiencing what sleep specialists call the first-night effect. The phenomenon has been confirmed by dozens of studies and is believed to have evolutionary roots, according to Anna Wick, a senior sleep researcher at the University of Freiburg in Switzerland.

“It’s assumed to be an adaptation response that the sleeping brain remains vigilant in this unfamiliar environment,” Wick said.

Ahmad Mayeli, a psychiatry professor and sleep researcher at the University of Pittsburgh, noted that most people experience it, and even those who do not notice it likely do on a minor level.

On average, individuals sleep about 20 to 30 minutes less in a new environment. His research found that the frontal lobe, an area linked to the deepest sleep stage, was more active, indicating a sense of alertness. Consequently, people sleep less overall and less deeply.

“They are saying that, like in dolphins, part of the brain is awake when you are sleeping,” Mayeli said. “It’s not exactly like dolphins, but still, studies show part of the brain is sleeping less.”

He noted that age makes a difference. The effect is more pronounced in children, adolescents, and older adults, and it typically worsens with age. Individuals in their 20s are the least affected.

“Maybe it’s the sweet spot,” he said.

Mayeli suspects that the human brain may be wired to be wary of new places because, historically, unaccustomed surroundings were the most dangerous during rest.

“It doesn’t matter if it’s a Marriott hotel or it’s the savannah,” he said. “Your brain hasn’t gotten the memo that this place is completely safe.”

Wick said evidence suggests the effect fades after the first night.

Lisa Strauss, a psychologist specializing in cognitive behavioral treatment of sleep disorders, noted that several factors can impact sleep in a new setting beyond evolutionary vigilance.

Travel itself can have a negative effect, even within the same time zone. Environmental factors may get in the way, like a flashing smoke alarm light in a hotel room. Relational tension, perhaps while visiting distant relatives, could also contribute.

Strauss observed that some people may sleep better the first night if they are exhausted after a long day of travel or if the new location provides a sense of detachment from daily stressors. People who have trouble sleeping at home might also fare better because they do not associate the new environment with a history of restless nights.

While anyone can experience the first-night effect, Strauss said those who are more anxious at baseline are especially vulnerable. It becomes a self-fulfilling prophecy—the worry about whether they can sleep is what keeps them awake. Leoni acknowledged there are times he enters the first night contemplating how he will sleep.

“Sometimes the thoughts come automatically,” he said. “You talk with your colleague, and you say, ‘I’m going back to the room, but I’m not going to sleep anyway.’”

Strauss recommends general sleep hygiene practices such as going to sleep in a cool, dark room at the same time every night, following a nighttime routine, and turning off screens well before bed. These steps are particularly helpful if started or resumed in the days or weeks prior to an important trip.

She suggested people try to make the environment their own by spending a little extra time in the new bed. They could read or engage in another peaceful, familiar activity to make the experience less novel, or bring familiar objects, like a favorite pillow or blanket.

For someone who is particularly anxious, Strauss recommended visualizing themselves in a safe, familiar environment, such as on a favorite hike or beach.

They should notice the anxiety they are feeling, then repeat positive phrases to help lower feelings of hypervigilance: “May you know that you are safe. May you know that you are loved. May you be at peace.”

Mayeli said the first-night effect is not really anything to worry about, and people can easily make up for missing an hour or two of sleep for one night. However, he recommends arriving a day early to acclimate before an important meeting or event.

“If tomorrow matters, get there a night early,” he said, “so you’ll sleep like yourself when it counts.”