If you’ve ever felt a growing sense of unease as Sunday evening arrives, you’re not alone. This phenomenon, commonly called the “Sunday scaries,” might not be an official diagnosis, but psychologists recognize this feeling as a form of anticipatory anxiety, or worry about future events that have not yet occurred. Even though researchers rarely use the exact phrase, studies on stress, hormones, and how our bodies react differently to weekends and workdays reveal why this feeling is so common. 

Scientific evidence shows that just thinking about upcoming stressors can activate the body’s stress response. In a study of 289 healthy adults, researchers found that people who spent more time engaged in future-directed thought when they felt stressed had higher cortisol levels, suggesting that anticipating stress can physiologically mimic experiencing it. Another study showed that people who ruminated or worried the night before a workday displayed an elevated cortisol awakening response (CAR) the next morning, a biological marker of anticipatory stress. Laboratory research also supports that the hypothalamic–pituitary–adrenal (HPA) axis can activate before an anticipated stressor, releasing cortisol in preparation for it. In other words, our bodies can experience stress just by expecting it, which is exactly what happens to so many of us on Sunday nights. 

Patterns in cortisol secretion further support the connection between weekends, workweeks, and stress anticipation. In a study of British civil servants, the cortisol awakening response was significantly greater on workdays than on weekends, indicating a measurable biological distinction between days associated with labor and days of rest. Another study tracking full-time workers across seven days found similar results: cortisol levels taken 30 minutes after awakening were higher on workdays than on Sundays, again showing that the body prepares itself for the cognitive and social demands of the coming week. These weekday-weekend physiological differences mirror the anxiety people report feeling on Sunday nights as they anticipate Monday.

Long-term evidence also supports a recurring “Monday effect” in stress physiology. A large longitudinal study of over 3,500 older adults in England found that participants who reported anxiety specifically on Mondays had 23 percent higher hair-cortisol concentrations, a biological measure of chronic stress exposure over approximately two months. Notably, this relationship held true even among retirees, suggesting the weekly rhythm of anticipation and anxiety can stick with us long after we stop working. The brain, it seems, keeps its own calendar. 

Put all this together, and a clear picture forms: as the weekend fades, we start mentally rehearsing the week ahead. That anticipation activates the HPA axis and raises cortisol, nudging the body into a mild fight-or-flight mode even before Monday begins. The shift from rest to routine becomes a biological stress trigger, causing both mental unease and physical tension. Over time, this recurring pattern can eat away at recovery, cutting into the very rest the weekend is supposed to provide.

While the term “Sunday Scaries” remains colloquial, the evidence shows that its biological foundation is real. Anticipatory anxiety has been clearly defined in psychological research, and multiple studies confirm that future-focused thoughts under stress elevate cortisol levels. The cortisol awakening response consistently rises on workdays compared with weekends, and those who experience more anxiety at the start of the week show higher long-term cortisol exposure. These measurable physiological markers demonstrate that Sunday-night stress is not simply cultural or emotional—it is embedded in the body’s stress-response systems.

In short, what people call the “Sunday Scaries” is the brain’s anticipatory alarm system, a neuroendocrine dress rehearsal for stress. The body ramps up cortisol as if Monday were a life-or-death scenario, even though the “predator” is usually just your inbox or a 9 a.m. class. It’s biology doing its best to protect us, just slightly confused about who the real enemy is (hint: it’s probably the Google calendar).