Dehydration is Making Your Anxiety & Depression Worse

Published August 14, 2025 06:00AM

It’s Monday morning after a hard brick workout in August, and you’re feeling…off. You became unusually angry when there was no oat milk at your favorite coffee shop, and after sitting in traffic for an extra 20 minutes, you felt pretty defeated by the time you got to work. Looking ahead at the week, you start to feel a sense of dread. The last straw was sending a snarky text to your wife after she asked you to pick something up at the grocery store on your way home.

Now you’re wondering: AITA? But the real question should be: Have I been drinking enough water?

As triathletes, we know that we need to stay hydrated during training and racing. Given the fact that we probably have three kinds of water bottle set-ups for the bike, two different kinds of hydration packs by the front door, and all the electrolyte tablets, powders, pills, and drinks money can buy, we probably don’t need another reminder that staying on top of fluid intake is crucial. However, you may not know that adequate hydration can also play a role in better mental health, even when you’re not training, and that feeling “off” can be a sign that you need to drink up.

Dehydration and mental health: The research

Research shows even mild dehydration can lead to low mood and feelings of depression and anxiety, along with impaired cognitive performance. In one study of male athletes, mild dehydration led to feelings of anxiety and increased tension. In another study, mild dehydration in exercising women led to low mood, a feeling that tasks were more difficult to complete, and general overwhelm. In both investigations, the effects continued until hydration was restored, meaning that the subjects experienced symptoms even after they were done training. A third experiment confirmed that subjects were likely to experience mental health effects even when exercise was not on the agenda.

Based on these findings, chronic dehydration could be continually affecting your mood and outlook, making you feel down even at times when you wouldn’t expect to need more water.

There is not enough research currently to explain the connection between hydration and cognition leading to mental health effects, but researchers believe that either electrolyte levels or complex stress signaling through the nervous system may be the culprit. In the absence of better information, the suggestion is to prioritize hydration – especially if you’re struggling with unstable moods or increased mental health concerns.

Hydration 101: A quick review

It’s remarkably easy to become dehydrated, especially in warmer weather. And while it’s easy to swig when you’re sweating more, you may not recognize that you need to do the same in windy or cooler conditions where you may not notice the moisture on your skin. The same goes for when you’ve had diarrhea, are taking certain medications, ate a salty meal, drank alcohol or caffeinated beverages, or even if you’re in the luteal phase of your menstrual cycle. Hydrating is not only about drinking water, though, and we often underestimate the amount of water that we get just by eating food. We get up to 20% of our fluid needs from the foods we eat – even bread is up to 40% water. Therefore, if you’ve been dieting or consuming less food for any reason, you may become dehydrated if you’re not compensating with additional fluid intake.

Though it’s difficult to estimate how much water adults should drink, most experts say that between 2.5 and 3.5 litres of water per day for non-active people is a good start. However, this doesn’t take hot weather into account, and certainly doesn’t consider a two-hour bike followed by a one-hour run session, where an athlete can require two or three times the normal volume of water. Mild dehydration is defined by a 1-2% loss (per body mass) of water, and it’s at this point that you can experience the cognitive effects like poor concentration and anxiety. It also makes your workouts feel harder.

It doesn’t matter how you drink or what you drink, so long as it hydrates you. So have the seltzer, the juice, the smoothie, or the tea – as long as it’s not an alcoholic beverage, it counts.

How to tell if dehydration is affecting your mental health

If you’re not sure if chronic dehydration is affecting your mental health, here’s how you can find out.

If you aren’t feeling lighter soon, it may be time to check in with a qualified mental healthcare professional. In the meantime, consider a sip to beat the snark and a chug to bring the cheer.