Monday anxiety is very real – and we now have the biological proof

July 13, 2025

Mondays leave a distinct stress-response mark on your body, new research finds

For the first time, scientists have found a distinct biological source of “Monday dread” that’s independent of work status and not seen in any other days of the week. What’s more, for some people, long-term stress triggered on Mondays is putting their heart at serious risk.

Researchers from the University of Hong Kong (HKU) found that Mondays, for many the start of the working week, has a unique impact on the body’s stress response and can trigger chronic issues that can be measured by lingering cortisol levels in hair.

“Mondays act as a cultural ‘stress amplifier,’” said Professor Tarani Chandola from the Department of Sociology, Faculty of Social Sciences at HKU. “For some older adults, the week’s transition triggers a biological cascade that lingers for months. This isn’t about work – it’s about how deeply ingrained Mondays are in our stress physiology, even after careers end.”

The study looked at the data of 3,511 adults aged 50 years and above, from the long-term, ongoing English Longitudinal Study of Ageing (ELSA, Wave 6, 2012–2013). These participants had all recorded stress levels for a Monday during their questionnaire sessions. They also provided hair samples to assess long-term stress hormone exposure, in particular cortisol and cortisone (a metabolite of cortisol). Because the samples were around 2 cm in length, sourced from the scalp, the researchers were able to measure stress hormone content across two to three months.

Data on age, sex, BMI, smoking, medication and socioeconomic status was also factored into the results and adjusted for.

What they found was that older adults who rated their anxiety levels on Mondays as the highest had a significantly greater level of hormones in their hair samples, indicating a sustained and chronic state of stress. This was seen across people who were both working and had retired, indicating that regardless of job status, the start of the week had a way of triggering this enduring stress response.

An earlier study found a link between Mondays and increased prevalence of severe heart attack. While the two studies are not directly associated, the increased biological stress associated with this one day of the week – and the mechanism triggered – offers clues to the biological process that sets the scene for cardiovascular disease.

That mechanism, the researchers found, was a disruption along the hypothalamic–pituitary–adrenal (HPA) axis, one of the body’s main stress response systems. The system forms a feedback loop between the hypothalamus and pituitary gland in the brain, and the adrenal glands that release cortisol. Normal regulation would see cortisol levels spike when the body perceives a threat, then return to baseline afterward. If the HPA axis has ongoing dysregulation, as seen in chronic stress and other conditions like PTSD, sustained cortisol levels can lead to cardiovascular disease, obesity, clinical anxiety and other cognitive impairments.

People who said they felt anxious specifically on Monday and not other days had, on average, 23% higher levels of cortisol in their hair compared to people who said they felt anxious on any other day. While everyone who reported anxiety had some level of cortisol detected, the researchers found that the most stressed people – 10% of respondents with the high cortisol levels – felt even more anxious when Monday rolled around.

So while many people may feel anxious on Mondays, only those with already high physiological stress seem to carry that anxiety into their biology, in the form of elevated long-term cortisol.

“Previous studies have shown some evidence for higher cortisol levels on weekdays than on weekends, although none have identified a specific anxious Monday effect,” the researchers noted. “As hair cortisol is an integrated measure of HPA axis activity over the preceding several months, this study could not identify whether cortisol levels are higher on Mondays. Instead, this study revealed an association between reported feelings of anxiety on Mondays and excessive levels of glucocorticoid production.”

More research is needed to identify specific cortisol spikes on Mondays, however, this study offers a clear biological response to Monday anxiety that’s felt by older adults regardless of work status. It also provides a path to targeting anxieties, especially for those in the highest risk category with chronic stress and elevated cortisol markers, who may be more likely to suffer from serious health issues as a result.

The study was published in the Journal of Affective Disorders.