Scientists at Harvard Medical School have discovered that the amount of “surprise” a person experiences in their day may help predict whether they will have a migraine attack within the next 12 or 24 hours.
This fresh insight adds a new layer to migraine research, suggesting that it is not always single triggers—like food, weather, or stress—that matter most, but how unusual or unpredictable a day feels overall.
For decades, people with migraines have been told to look for possible triggers such as red wine, chocolate, poor sleep, strong smells, or stressful events. The problem is that most people track these triggers by memory, often after the migraine has already begun.
There are too many possible triggers to monitor, and they change from one person to another. Many individuals also struggle because controlled experiments are not practical in their daily lives. This new study offers a different way of thinking about the problem.
The research, published in JAMA Network Open, examined a concept called “trigger surprisal.” Surprisal measures how unusual or out-of-the-ordinary a person’s daily experiences are compared to what is normal for them.
Instead of focusing on a long list of single triggers, surprisal looks at the entire day as a whole. If a person has a day that feels unusual—emotionally, behaviorally, or environmentally—their risk of a migraine increases.
To explore this, researchers followed 109 adults diagnosed with migraine according to international headache guidelines. All participants experienced between four and fourteen headache days per month and were between the ages of 18 and 65. They completed electronic diaries twice a day for up to 28 days.
These diaries collected information about sleep quality, wake times, nighttime awakenings, mood, late-night meals, weather, daily stressors, food and drink intake, and environmental changes.
Across the study, participants recorded headaches on 1,518 out of 5,145 total diary days. Using the diary responses, the researchers calculated each person’s surprisal score—how different that day’s experiences were from their usual patterns.
The results showed a clear trend: when a person had a day that was very different from their normal routine, their risk of a migraine attack increased sharply over the next 12 to 24 hours. At 12 hours, their odds went up by about 86 percent. At 24 hours, the risk increased by around 115 percent. The association was even stronger at the longer time interval.
But the study also found something interesting. Surprisal does not affect everyone equally. Some people were extremely sensitive to unusual days, while others showed almost no connection between surprise and migraines.
For people who already had a high baseline risk—those who frequently had headaches—surprisal was a weaker predictor. Their migraines may be driven more by internal biological factors than by daily life changes.
The researchers also observed that the effect of surprise depends on the previous day. If the previous day was very typical, then an unusual day causes a big increase in migraine risk.
But if the previous day was already unusual, another unusual day adds less additional risk, especially within the next 12 hours. Over 24 hours, more surprise still increased migraine risk, but the effect became weaker.
These findings suggest that keeping daily life more stable—regular sleep patterns, consistent routines, steady emotional habits—might help prevent migraines by reducing surprisal. Instead of trying to avoid dozens of specific triggers, people might benefit from focusing on general stability and stress reduction.
The study also points toward practical tools for the future. Researchers believe surprisal could be built into apps that help predict migraine risk in real time. These apps could analyze a person’s daily routines and warn them when their day is unusually irregular, giving them a chance to rest, plan ahead, or take preventive medication.
However, the researchers also caution that the study had some limitations. The sample size decreased from a planned 200 participants to 109 because of COVID-19 disruptions.
This made it harder to analyze how surprisal affects different age groups or migraine types. The study also did not fully account for medication use or other health factors that might influence migraine patterns.
In reviewing the study findings, the results highlight a meaningful shift in how migraines may be understood. Instead of hunting for single triggers, it may be more helpful to observe how the overall rhythm of life affects the brain.
The study strongly supports the idea that the brain reacts to change, unpredictability, and sudden shifts in behavior or emotion. While more research is needed, surprisal offers a promising way to predict and manage migraine risk in everyday life.
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