Groundbreaking new study finds link between stress and how much water you drink

We’re in a golden age of hydration, with younger generations glugging down water as if it’s good for them.

The good news is: it’s very good for them.

Dehydration, even at low levels, can cause all kinds of discomforts. Headaches, fogginess, confusion, general discomfort and poor concentration are typical early signs, and once your pee is on the yellow side it’s safe to say your kidneys are parched.

It’s recommended that you drink two litres of the stuff per day, but you may well need more in warm conditions or if you live an active lifestyle.

Reusable water bottles have become a mainstay in younger people's lives (Klaus Vedfelt/Getty Images)

Staying well hydrated ensures your body has all the water it needs for its processes and waste management, it can help to manage your appetite, and it’ll keep your organs happy.

Apparently, it also helps to manage stress.

A new study published in the Journal of Applied Psychology, found that people who drank fewer than 1.5 litres of water each day had significantly higher levels of cortisol in their systems. Cortisol is the main stress hormone and has a major influence on your fight-or-flight response.

Once you’ve released it, it lingers in your system and needs to be flushed out in your waste matter.

The study’s findings show that, even if you’re consuming 75% of the recommended intake, you’re holding onto more cortisol than you would if you were properly hydrated.

Researchers took two groups of healthy adults and had one drink 1.5 litres of water per day while the second group drank more than the recommended minimum: two litres per day for women, and 2.5 litres for men.

After following this regimen for a week, the participants had their stress levels measured in a lab. During the tests, they performed public speaking and mental maths exercises.

While both groups found the tests similarly stressful, the low-water group had a much stronger increase in cortisol levels. If this were repeated over months or years, as would be the case for the chronically under-hydrated, this could lead to heightened risk of heart disease, kidney issues and diabetes.

Interestingly, the under-hydrated group didn’t report heightened thirst despite their urine being considerably darker. This points to thirst levels being a poor indicator of whether we’re properly hydrated.

“The mechanism behind this stress amplification involves the body’s sophisticated water management system,” said the researchers in The Conversation.

“When dehydration is detected, the brain releases vasopressin, a hormone that instructs the kidneys to conserve water and maintain blood volume. But vasopressin doesn’t work in isolation, it also influences the brain’s stress-response system, potentially heightening cortisol release during difficult moments.”

Even mild dehydration had a major impact on participants' stress levels (ingwervanille/Getty Images)

They continued: “This creates a physiological double burden. Although vasopressin helps preserve precious water, it simultaneously makes the body more reactive to stress. For someone navigating daily pressures – work deadlines, family responsibilities, financial concerns – this heightened reactivity could accumulate into significant health harms over time.”

In other words: drink up! There are simply too many short and long-term benefits of proper hydration to ignore.