The story begins not in a lab but in the quiet, unpredictable rhythm of daily life. A slightly worse night of sleep. A skipped lunch. A burst of unexpected stress. A strange shift in the weather. These moments often feel like small disturbances, barely worth noting. But for people living with migraine, even subtle changes can feel like tremors hinting at something larger beneath the surface.
Researchers at Harvard Medical School wondered whether the very feeling of a day being “different” could itself be a clue. Could the sense of surprise—of life departing from its normal pattern—be a measurable signal of an impending migraine? Their investigation followed that intuition into the intimate details of daily routines and emerged with a discovery: the more unexpected the day felt, the higher the risk of a headache attack in the hours that followed.
A Study Built From the Texture of Real Life
The research, published as “Information-Theoretic Trigger Surprisal and Future Headache Activity” in JAMA Network Open, followed 109 adults with migraine, all diagnosed based on the International Classification of Headache Disorders, 3rd Edition criteria. These volunteers lived with four to 14 headache days each month. From ages 18 to 65, they represented a community accustomed to the constant negotiation of triggers, routines, and the hope for relief.
For up to 28 days, each participant filled out electronic diaries twice daily—once in the morning and once in the evening. These weren’t vague reflections or broad checklists. They were detailed snapshots of daily life, designed to capture the full landscape of potential migraine influences. Morning diaries asked about sleep duration, awakenings, bedtime and wake time, late-night meals, weather, and mood. Evening entries revisited mood and added foods and drinks often suspected as triggers, environmental exposures, missed meals, weather, and the day’s stressors.
Headaches appeared on 1,518 of the 5,145 days with complete diary data, offering a textured record of what life looked like right before migraine struck—and what it looked like when it didn’t.
Instead of focusing on individual triggers—chocolate, stress, red wine, bright light—the researchers used each diary entry to calculate a “surprisal score,” a number that captured how atypical a given day was compared to that person’s usual pattern. Every participant thus became their own reference point, their own baseline, their own measure of what counted as normal.
When Patterns Break, Risk Rises
The findings revealed a delicate relationship between everyday unpredictability and migraine onset. Higher surprisal scores—days that felt unusual—were associated with greater odds of a headache attack in the next 12 and 24 hours. Even after accounting for recent headache history and the natural fluctuations of daily experiences, the link held strong.
The numbers were striking. The total surprisal score rose alongside the odds of a future attack—by 86 percent in the next 12 hours and 115 percent in the next 24 hours. Over the longer window, the relationship grew even stronger.
But the story was not simply linear. It shifted depending on what came before.
If the previous day was normal, then the risk climbed sharply as surprisal increased. A single unusual day could push the odds of a migraine noticeably higher. Yet if the previous day had already been atypical, another unusual day added much less risk—and in the 12-hour window, the model even showed that risk could dip slightly. Over 24 hours, surprise still increased risk, but not as strongly when the previous day had already indicated unsettled routines.
The researchers described it simply: “Surprisal score analysis showed that when a person has a day which feels very different from their usual routine, migraine risk over the next 12 to 24 hours tends to increase.”
Different Brains, Different Reactions
Of course, the relationship between daily life and migraine is never the same for everyone. Some participants showed a very strong sensitivity to unusual days. Others showed almost none. For people whose baseline migraine risk was already high, surprisal had less predictive value. Their headaches appeared less connected to daily shifts and more tied to factors beyond behavioral or environmental changes.
This variability didn’t weaken the finding—it strengthened its significance. The goal was never to present surprisal as a universal law, but as a potential individualized measure of risk, reflecting the unique rhythm of each person’s life.
What Surprisal Really Means
Interpreting surprisal requires a shift in perspective. Traditional migraine management leads people to hunt for specific culprits: a certain food, a type of light, a stressful conversation. But this study suggests that the overall “texture” of the day matters just as much as any single factor. Surprisal captures something subtle but powerful—the emotional and experiential sense that “today wasn’t like other days.”
Instead of dozens of yes-or-no trigger checkboxes, surprisal recognizes that daily life is a dynamic system. When that system is disrupted, the body may respond in ways that increase migraine vulnerability.
The researchers note that surprisal “reflects how out-of-the-ordinary someone’s day feels, rather than focusing on specific ‘yes/no’ triggers.” They suggest the scores could be incorporated into apps designed to forecast migraine risk in real time, offering personalized insights based on a person’s evolving routine.
Their conclusion hints at a future shift in migraine management: “Instead of avoiding specific triggers, approaches that support steadier routines or emotional regulation might help reduce surprisal and resulting attacks.”
A Study Shaped by Its Limitations
The team acknowledged that the sample size was smaller than planned. Originally aiming for 200 participants, they reached 109 because of pandemic-related disruptions. This limited the ability to examine detailed subgroups such as age ranges or headache subtypes and meant that some relevant influences, like medication use, could not be fully explored.
Even so, the richness of the diary data and the depth of statistical analysis allowed the researchers to trace meaningful patterns from the complex fabric of daily life.
Why This Research Matters
This study matters because it reframes the migraine experience in a way that feels closer to reality. People living with migraine often describe their days in terms of stability or disruption, of routines that hold steady or fall out of sync. Surprisal gives scientific shape to that intuitive sense. It shifts attention from hunting individual triggers to understanding the ebb and flow of daily life as a whole.
By showing that a day’s unusualness, rather than specific events, can foreshadow a migraine, the study opens the door to new strategies for prediction and prevention. It hints at tools that respond to personal patterns rather than generalized rules, and at self-management approaches grounded in steadiness, emotional awareness, and the rhythms that help life feel familiar and calm.
Most importantly, it offers people with migraine a new lens through which to understand their own experience: not as a mystery of isolated triggers, but as a story shaped by the full tapestry of their days—where even small surprises can speak volumes.
More information: Dana P. Turner et al, Information-Theoretic Trigger Surprisal and Future Headache Activity, JAMA Network Open (2025). DOI: 10.1001/jamanetworkopen.2025.42944
