Drinking Less Fluids May Increase Stress Hormone Levels

Cortisol response to stressful events is higher in dehydrated young adults, study finds. 

Rockville, Md. (Oct. 16, 2025)—Not drinking enough fluids could lead to a greater stress response in the body, according to a study published in the Journal of Applied Physiology.  The article has been chosen as an APSselect article for October. 

Dehydration has previously been linked to a higher risk of heart and kidney disease, in part because low water intake causes a key water-regulating hormone to increase. When this hormone, called arginine vasopressin, spikes, it prompts the body to produce more of the stress hormone cortisol. Too much cortisol can be a predictor of future health problems.

Researchers at Liverpool John Moores University in the U.K. examined the relationship between hydration levels (whether someone is dehydrated), fluid intake and cortisol. They analyzed the urine of volunteers ages 18 to 35 to determine their hydration level, low or high. The volunteers recorded everything they drank (water, milk, juice, soft drinks, alcohol, tea and coffee) for seven days. The research team monitored the participants to ensure they maintained their normal fluid intake patterns during the week before the stress test.

The participants also took several questionnaires about their levels of stress, anxiety and their quality of sleep. On the eighth day of the trial, the volunteers participated in a mock job interview and performed mental math problems while standing in front of two observers. They believed these stress-inducing activities were being recorded—another potentially stressful situation—but they were not.

To measure the participants’ levels of cortisol, researchers took saliva samples before, immediately afterward and several more times in the hour after the stress tests. The participants’ anxiety levels and heart rates increased. The low hydration group—those who did not drink as much fluid—had higher levels of cortisol in their saliva than the high hydration group. In addition, the low hydration group had greater increases in cortisol in response to the stressful activities.

“These findings highlight the importance of accounting for fluid intake and hydration status when assessing cortisol reactivity to psychosocial stress,” the researchers wrote.

Read the full article, “Habitual Fluid Intake and Hydration Status Influence Cortisol Reactivity to Acute Psychosocial Stress.” It is highlighted as one of this month’s “best of the best” as part of the American Physiological Society’s APSselect program. Read this month’s selected research articles.   

NOTE TO JOURNALISTS: To schedule an interview with a member of the research team, please contact APS Media Relations or call 301.634.7314. Find more research highlights in our Newsroom.   

Physiology is a broad area of scientific inquiry that focuses on how molecules, cells, tissues and organs function in health and disease. The American Physiological Society connects a global, multidisciplinary community of more than 10,000 biomedical scientists and educators as part of its mission to advance scientific discovery, understand life and improve health. The Society drives collaboration and spotlights scientific discoveries through its 16 scholarly journals and programming that support researchers and educators in their work.