That familiar slump that hits every spring, the urge to nap through the afternoon and drag through mornings despite longer days, may have less to do with biology than belief. A new large-scale study published in the Journal of Sleep Research finds no consistent evidence that fatigue, sleepiness, or insomnia symptoms change measurably across the seasons, challenging the widespread notion that humans experience a distinct “spring fatigue” syndrome.
The research, led by a team of sleep scientists who analyzed data from thousands of participants across multiple years, directly tested whether seasonal transitions produce measurable shifts in three core sleep-related complaints. The answer, across nearly every analysis, was a clear no.
What they found
The study examined data from repeated surveys and diary measures in which participants self-reported fatigue, daytime sleepiness, and insomnia symptoms at different times of year. The researchers tested for seasonal patterns using multiple statistical methods, including cosinor analysis, a technique designed to detect cyclical rhythms in biological data.
None of the analyses found a reliable seasonal signal. Fatigue scores did not spike in spring relative to other seasons. Sleepiness ratings remained stable across winter, spring, summer, and fall. Insomnia symptoms fluctuated no more than would be expected by chance.
The null result held even when the researchers stratified the data by age, sex, latitude, and climate zone. People living in regions with harsh winters and dramatic seasonal shifts in daylight were no more likely to show seasonal variation in sleep symptoms than those in mild, stable climates.
The study’s title states the conclusion plainly: “Spring fatigue is a cultural phenomenon rather than a seasonal syndrome.”
Why it matters
The idea that humans, like many animals, experience biologically driven seasonal shifts in energy and sleep has deep cultural roots. In many countries, spring fatigue is discussed in popular media as a predictable, almost unavoidable annual event. Advice columns, wellness blogs, and even some medical websites offer tips for “beating spring fatigue,” implicitly endorsing the idea that it is a real physiological condition.
The new findings suggest that the perception of seasonal fatigue may be driven by expectation rather than biology. When people believe that spring fatigue is real, they may selectively notice and attribute normal fluctuations in energy to the change of season, reinforcing the cultural narrative. The phenomenon, the authors argue, is better understood as a shared cultural belief than as a recurring medical condition.
This distinction matters for clinical practice. If patients present with springtime complaints of fatigue or poor sleep, clinicians may be tempted to attribute them to the season and defer further investigation. The study suggests that such symptoms warrant the same diagnostic attention they would receive at any other time of year. Attributing them to a seasonal cause that does not actually exist risks missing underlying issues, including mood disorders, sleep apnea, anemia, or thyroid dysfunction.
The research also speaks to a broader question in sleep science: how much of what we experience as seasonal variation in sleep is genuinely biological, and how much is culturally constructed. While seasonal changes in circadian rhythms are well documented in controlled laboratory settings, their real-world effects may be small enough that they are easily drowned out by individual differences, lifestyle factors, and social expectations.
Limits
The study relied on self-reported measures of fatigue, sleepiness, and insomnia rather than objective physiological data such as actigraphy or polysomnography. It is possible that seasonal changes exist at the level of brain activity or circadian phase alignment that participants do not consciously register as changes in sleep quality or energy.
The researchers also note that their sample, while large, was drawn primarily from populations in industrialized countries with relatively stable indoor environments. In settings where seasonal changes impose more drastic shifts in temperature, daylight exposure, or daily routines, measurable seasonal effects on sleep may emerge.
Finally, the study cannot rule out the possibility of very small seasonal effects. The data were robust enough to rule out moderate-to-large seasonal changes, but subtle shifts below the detection threshold of the current analyses could still exist.
Bottom line
Spring fatigue, as a distinct seasonal syndrome, does not appear to exist in any consistent, measurable form. The persistence of the idea likely reflects cultural scripts and selective attention rather than an underlying biological rhythm. For most people, feeling tired in spring is not a predictable seasonal event, but a normal part of the human experience that deserves the same thoughtful attention as any other complaint.
Source
Wrzus, C., & Riediger, M. (2026). No Evidence for Seasonal Variations in Fatigue, Sleepiness and Insomnia Symptoms: Spring Fatigue Is a Cultural Phenomenon Rather Than a Seasonal Syndrome. Journal of Sleep Research, e70319. https://doi.org/10.1111/jsr.70319