Any long-distance traveler will recognize the discomfort that comes from hopping across multiple time zones: the restless nights and drowsy afternoons, accompanied by mental fog, irritability and reduced appetite. The general malaise of jet lag can dampen my excitement for the first few days of any trip—so I was pleased to learn that a simple shift in mindset could provide some relief.
According to the prevailing theory, jet lag is an inevitable result of disruptions to the body’s circadian clock. In normal life, the brain has come to predict the timing of night and day and directs our sleep cycles accordingly. If we were traveling by land or sea, it could slowly adapt to each new time zone. The speed of air travel, however, means that the internal clock doesn’t have a chance to synchronize.
In recent years, however, scientists have become increasingly interested in the ways that our expectations can shape the symptoms of many ailments that were once considered to be purely physiological in origin. If people are led to believe that they will get a bad headache, for instance, they are much more likely to develop throbbing pain. This discomfort is not merely imagined but is accompanied by measurable changes in the brain’s chemistry, and—crucially—it can be reversed by creating expectations of relief.
Scientists have now documented “expectation effects” in many areas of life—including the quality of our sleep. Studies show that the more people worry about insomnia and its effects, the more likely they are to experience difficulties falling asleep, and the worse their symptoms will be the next day. One team of researchers gave participants sham feedback about their sleep quality and then measured their fatigue and cognitive abilities the following day. If the participants were told they’d had a bad night, their minds acted as if that were true, with poorer mental focus.
Given this growing list of self-fulfilling prophecies, it would make complete sense that our symptoms of jet lag could also be influenced by our expectations—and that is exactly what scientists from Ludwig Maximilian University of Munich have found. The researchers asked 90 participants who had booked long-haul flights to record their expectations of jet lag and how much they thought they would suffer. They then completed daily questionnaires about their sleep, focus, energy levels, appetite and mood for one week before and one week after their long-haul flight.
If jet lag were purely the result of changes to the circadian rhythm, then the number of time zones traveled should have been the best predictors of the passengers’ symptoms. Yet their expectations proved to be the defining factor. The more the travelers worried about jet lag, the worse their experience—even after controlling for the distance and direction of travel. On average, people with the most pessimistic expectations about the duration of their jet lag suffered reported symptoms that were twice as severe as those who thought they’d recover within the first 24 hours.
We can combat negative expectations with a process called “cognitive restructuring.” The first step is to spot “catastrophizing,” in which our thoughts start to descend in a negative spiral. If we feel restless in a hotel bed, we might start telling ourselves, I’m going to be awake all night. Then we might think, I just cannot function tomorrow. Once we have noted that cycle, we can ask ourselves if we are exaggerating the distress that we will feel, and remind ourselves that we may be better able to cope than we think. This technique has been proven to help people with insomnia, and the same process should be beneficial for the symptoms of jet lag.
Personally, I find I can break the catastrophic thinking by making a mental list of all experiences I am most looking forward to on my trip. I recently put this into practice on a series of transatlantic flights, and I’ve never felt fresher during my travels.
David Robson is an award-winning science writer based in London. His latest book, The Expectation Effect: How Your Mindset Can Change Your World (Henry Holt), was a Financial Times Best Book of 2022 and won a British Psychological Society Book Award in 2022.