Dehydration and Mental Health: What’s the Connection?

There’s a strong relationship between dehydration and mental health. Low fluid levels can cause hormone changes, cognitive impairment, poor sleep and a host of other unpleasant physical symptoms that can bring down your mood.

That may help explain the findings of two studies: One from 2018 and one from 2024. Read together, they found that people who drink less water are more likely to say that they feel anxious, depressed or suicidal.

Nobody is claiming that water is the cause (or solution) of mental illness. But these and other studies demonstrate that water plays a vital role in our state of mind.

To better understand the connection, psychologist Susan Albers, PsyD, breaks down the neurological and psychological impact of dehydration and offers some hydration hacks to help boost your spirits.

How dehydration impacts mental health

On average, about 60% of your body weight is water. So, it probably isn’t surprising that there’s a link between hydration and mental health. Dehydration impacts your body and brain so much that Dr. Albers makes a point of asking about it in her sessions.

“I ask how much water people are drinking when they come in because it can shape your mood in powerful ways, just like food and sleep do,” she shares. She recommends taking a mental inventory of your water consumption every day.

“You don’t have to have a mental health diagnosis for dehydration to impact your mood,” Dr. Albers clarifies. “Many of the symptoms are mild but significant. And together, they add up.”

Being dehydrated:

Causes hormonal imbalances

When you aren’t drinking enough water, production of the stress hormone cortisol increases. In response, happy hormone production declines. Suddenly, you’re short on feel-good neurotransmitters like serotonin, dopamine and oxytocin. That hormonal imbalance can make you irritable, sad, exhausted and more.

Prompts a fight-or-flight response

Here’s the thing about hormone imbalances: They don’t just impact your mood. They also affect other bodily functions.

“When your cortisol level is raised, it kicks you into ‘fight-or-flight’ mode,” Dr. Albers explains. “When that happens, you start experiencing symptoms that feel like anxiety.” Among other sensations, you may notice:

• Rapid heartbeat
• Fast breathing
• Sweating
• Muscle tension

You don’t have to be anxious to feel anxious. Those symptoms alone are enough to throw off your mood.

Makes you physically uncomfortable

Being dehydrated does provoke a fight-or-flight response. But it also makes you feel … well, crummy. And it’s hard to keep the vibe high when you’re not feeling well.

In addition to the symptoms we’ve already mentioned, dehydration can cause headaches, fatigue, muscle cramps, constipation and more.

“Physical well-being is intricately linked with mental health,” Dr. Albers emphasizes. “When your body isn't feeling its best, your mind often follows suit.”

Impacts cognitive function

Dehydration throws your electrolytes out of balance. Electrolytes are electronically charged minerals like sodium, calcium, magnesium, potassium and more. Among many other responsibilities, electrolytes regulate your cognitive functioning. When they’re out of whack, it can affect a wide range of processes, including:

• Attention
• Executive functioning skills
• Learning
• Decision-making
• Memory
• Processing speed
• Use (and understanding) of language

The result is often referred to as “brain fog.”

“I think people underestimate the link between brain fog and dehydration,” Dr. Albers stresses. “Your brain needs enough fluid for the connection between nerves to run effectively. Staying hydrated helps your brain work at its best, keeping you sharp, focused, and clear-headed.”

Brain fog and depression often go hand in hand.

If you’re dealing with short-term dehydration, there’s good news: Multiple studies suggest that drinking water improves your cognitive function quickly.

But if you’re chronically dehydrated, the opposite can also be true.

“Long term, dehydration can impact your brain and those neural connections,” Dr. Albers adds. That makes sense because studies suggest that — dehydrated or not — cognitive problems can continue even after your mood and other depression symptoms have resolved.

Messes with your sleep

We all know, arguably too well, that not getting enough sleep is a recipe for a bad mood. Well, dehydration is a recipe for a bad night’s sleep.

“One of the No. 1 reasons people don’t drink enough water is that they don’t want to be back and forth to the bathroom all day long. That fear is even greater in the middle of the night because they’re afraid it’ll interrupt their sleep,” Dr. Albers explains. “But being dehydrated actually makes it harder to fall and stay asleep.”

She recommends slowing down or stopping drinking about two hours before you hit the hay. But don’t worry about the consequences of drinking a big glass of water at dinner: It’s more likely to help than hurt.

Hydration tips for mental health

“Dehydration and mood are like a seesaw,” Dr. Albers illustrates. “As your water intake goes down, your stress levels go up.” That’s part of the reason why it’s harder to take care of yourself when you’re feeling depressed or anxious.

It’s a vicious cycle. When you’re in a bad place, mentally, it can impact your executive functioning skills, making you less likely to drink water regularly. Being dehydrated can make you feel even worse, which can make you even less likely to get the water you need!

If your mental health is impacting your self-care routine, Dr. Albers recommends trying the following hydration hacks:

• Automate it. Use alarms to remind you to drink throughout the day.
• Try habit stacking. If hydrating doesn’t feel like second nature, link it with activities that do. This trick, often called habit stacking, can help make healthy behaviors automatic.
• Frontload your fluid intake. “Drinking a glass of water first thing in the morning is great for your mental health,” Dr. Albers recommends. “Getting hydrated right off the bat will improve your functioning throughout the rest of the day.”
• Commit to tracking. If you love the feeling of checking off a box, consider using a tracking app on your phone. Or keep it old-school and use pen and paper!
• Always carry a water bottle with you. If you’ve got it, you’ll use it. Want to be extra sure? Dr. Albers recommends mapping out the water fountains at your office, school, gym and more.
• Limit caffeine and alcohol. “You may feel like you’re drinking enough water. But caffeine and alcohol are both diuretics,” Dr. Albers explains. “If you’re drinking too much of either, or drinking them exclusively, they can suck out all of the hydration and undo your hard work.”
• Eat hydrating foods. “A percentage of our hydration comes directly from food,” Dr. Albers notes. “So, I always recommend having a bag of grapes, cucumbers or another food with high water content available. It’s extra helpful if you’re not crazy about water.”
• Make it fun. There are many ways to gussy up your water without piling on the calories or additives. Mineral water and seltzer are great options. So is adding fresh fruit.
• Practice mindfulness. Dr. Albers suggests checking in with yourself throughout the day. “Ask yourself honestly how you feel mentally and physically,” she says. “If you know the red flags that signal dehydration and consistently tune into your body, sometimes you can catch it early.”
• Focus on electrolytes. Water isn’t the only name in the hydration game. “Electrolytes matter for everyone. They’re even more important if you have certain medical conditions or an active lifestyle,” Dr. Albers emphasizes. Coconut water, herbal teas and milk are all rich in electrolytes. Prefer H2O? Add Celtic sea salt to your water or place it under your tongue before taking a sip. That will help you absorb water more quickly.

Final thoughts

Staying hydrated is extremely important to keep our bodies and minds healthy. But as Dr. Albers stresses, mental health is multifaceted.

“Hydration is a tool, not a cure,” she says. “Water helps keep your engine running, but it won't fix a flat tire. You need several other tools in the mix to do that. Nutrition, sleep, exercise, social support and, in some cases, a mental health professional and medications — they all have a role to play.”