At some point in our distant evolutionary past, when we were perhaps still lemurs or some other sort of tree-roving monkey, we developed an emotion that would prove essential to keeping us safe: anxiety.
Anxiety made us think twice before leaping into an open prairie, or taking a drink from a crocodile-infested river. It made us reconsider before swinging through the very same tree where our cousin was mercilessly squeezed by an anaconda.
Even today, anxiety helps to keep us safe from harm. But there’s fewer threats in our modern, civilised world, and sadly, our brains can’t tell the difference, so we’re cursed to experience more anxiety than we need to. But thankfully, we can do something very simple to reduce our anxiety levels—drink more water!
Dehydration can make us more anxious and depressed
Can drinking more water help with anxiety? Absolutely. Multiple studies have shown that drinking more water can help to reduce symptoms of anxiety and depression. In 2019, a handful of scientists got together to complete a comprehensive review of hydration studies, focusing on the various ways in which hydration impacts our health. Some of their findings were astonishing, particularly those related to anxiety and depression.
They found that dehydration didn’t just make people more tense and anxious, but also more angry, confused, and tired—a selection of unpleasant moods and emotions that can lead to even more anxiety and feelings of depression. They also found that dehydrated people had an impaired working memory and worse focus1, which would presumably make daily tasks more difficult to get through, and again, lead to increased feelings of anxiousness, irritability, and sadness. The brain tissue is 75% water, so if we forget to top it up, it literally impairs our brain’s function. Being well-hydrated makes you sharper, more focused, and more calm, which can help you to accomplish your goals and lead to feelings of contentment.
In another large study with 3,327 people, scientists found clear associations between water consumption and depression, and a less substantial link for anxiety (although feelings of depression and anxiety often influence each other). In the study, those who drank fewer than two glasses of water a day had double the risk of depression and anxiety compared to those who drank five glasses—an incredible risk increase that can be deterred by drinking more water2. Depression also happens to be a symptom for those who are chronically dehydrated, which is more proof of how badly dehydration can affect our mental health.
In 2014, a smaller study with 52 people tested the effects of hydration on two groups of people: those who drank lots of water each day (2 to 4 litres) against those who drank less each day (less than 1.2 litres). For the high water consumers, drinking less water made them feel less content, less energetic, and less calm (i.e. more anxious). For the low water consumers, drinking more water didn’t reveal a direct change in anxiety, but it did make them feel less confused, less sleepy, and more energetic, all of which can contribute to feelings of anxiety3. And when the researches increased the water intake for both groups, they recorded greater feelings of happiness, regardless of how much they usually drank.
A study in the following year confirmed similar results: reducing water intake made 120 women feel more tense, confused, and depressed4. And four years prior, a different study found the exact same results for 26 men5, as well as affecting their working memory, and worsening their anxiety. These studies show little difference between the sexes—dehydration has an array of health consequences in both cases, including making them more anxious.
It isn’t just our waking hours that drinking water can improve. Drinking more water might also affect how well we sleep7, and when we’re sleep deprived, we can become even more dehydrated, and much more anxious. The effect is circular too—a study of 20,000 people who slept only six hours a night were found to be much more dehydrated than people who slept for longer10. So dehydration leads to bad sleep, and bad sleep leads to even more dehydration, with the result being a potential spike of anxiety.
Of course, we should be careful not to drink too much water before going to bed, so that we’re not breaking our sleep pattern to repeatedly visit the bathroom (a condition called nocturia).
Why dehydration affects our mood
As mentioned above, our brain tissue is made up of 75% water, and our entire bodies are 60%. Almost every one of our bodies’ functions are reliant on water—it’s a key nutrient we need to run efficiently.
From a chemical perspective, water affects a few key processes in our bodies. Serotonin is a jack-of-all-trades hormone whose core functions include stabilising our mood and feelings of happiness. Our body needs a chemical called tryptophan to produce serotonin, and when we’re dehydrated, we struggle to get this chemical into our brain where the production takes place7. In addition to this, dehydration can affect how our bodies produce key amino acids, and when combined with reduced serotonin, can lead to feelings of anxiety, dejection, irritability, and inadequacy8.
Dehydration also increases the stress hormone cortisol in our body, with studies showing spikes after drinking just half a litre less. It’s a vicious circle too—the less you drink, the more stressed you get, which increases your heart rate and makes you even more dehydrated. If you have an anxiety disorder or are feeling more anxious than usual, as more and more stress piles on, you may find yourself in the grip of a panic attack. This risk is made even worse by the fact that dehydration feels very similar to anxiety—dizziness, feeling faint, fatigue, headaches, increased heart rate, and nausea—which can cause you to start panicking in the first place.
While water certainly isn’t an anxiety cure, it can help to reduce your overall anxiety levels, as well as a range of other issues such as depression, impaired memory and focus, irritability, and fatigue. It can also help you to get better sleep, which further improves your body’s hydration and anxiety levels.
The evidence is clear: drink the recommended 8 glasses of water a day. It has a huge number of health benefits, one of which is reducing your overall anxiety, and making you a happier, healthier person.
- DeAnn Liska, Eunice Mah, Tristin Brisbois, Pamela L. Barrios, Lindsay B. Baker, Lawrence L. Spriet, 2019, Narrative Review of Hydration and Selected Health Outcomes in the General Population, Nutrients, MDPI
- Fahimeh Haghighatdoost, Awat Feizi, Ahmad Esmaillzadeh, Nafiseh Rashidi-Pourfard, Ammar Hassanzadeh Keshteli, Hamid Roohafza, and Payman Adibi, 2018, Drinking plain water is associated with decreased risk of depression and anxiety in adults: Results from a large cross-sectional study, World Journal of Psychiatry
- Nathalie Pross, Agnès Demazières, Nicolas Girard, Romain Barnouin, Déborah Metzger, Alexis Klein, Erica Perrier, Isabelle Guelinckx, 2014, Effects of Changes in Water Intake on Mood of High and Low Drinkers, Plos One
- Colleen X Muñoz, Evan C Johnson, Amy L McKenzie, Isabelle Guelinckx, Gitte Graverholt, Douglas J Casa, Carl M Maresh, Lawrence E Armstrong, 2015, Habitual total water intake and dimensions of mood in healthy young women, National Library of Medicine
- Matthew S Ganio, Lawrence E Armstrong, Douglas J Casa, Brendon P McDermott, Elaine C Lee, Linda M Yamamoto, Stefania Marzano, Rebecca M Lopez, Liliana Jimenez, Laurent Le Bellego, Emmanuel Chevillotte, Harris R Lieberman, 2011, Mild dehydration impairs cognitive performance and mood of men, National Library of Medicine
- Asher Y Rosinger, Anne-Marie Chang, Orfeu M Buxton 1, Junjuan Li, Shouling Wu, Xiang Gao, 2019, Short sleep duration is associated with inadequate hydration: cross-cultural evidence from US and Chinese adults, National Library of Medicine
- N K Popova, L N Ivanova, T G Amstislavskaya, N N Melidi, K S Naumenko, L N Maslova, V V Bulygina, 2001, Brain serotonin metabolism during water deprivation and hydration in rats, National Library of Medicine
- 2020, The Connection Between Dehydration and Depression | Optimum Water, Drink Optimum
- Gina Shaw, Water and Stress Reduction: Sipping Stress Away, WebMD
- Asher Y Rosinger, Anne-Marie Chang, Orfeu M Buxton, Junjuan Li, Shouling Wu, Xiang Gao, 2019, Short sleep duration is associated with inadequate hydration: cross-cultural evidence from US and Chinese adults, National Library of Medicine