Key points
- Water helps produce neurotransmitters, making adequate hydration essential for optimal psychological health.
- Adequate water intake is correlated to better cognitive performance and a decrease in depression and anxiety.
- Too much water, however, can dilute sodium and potassium levels and cause neuropsychiatric complications.
We always hear it’s important to stay hydrated, but aside from the obvious, like flushing out toxins and not feeling like a raisin, have you ever wondered why water is so important to our health?
It seems that nowadays drinking water has become trendy, or at least the water containers have, leading to inadvertently well-hydrated otherwise hydrophobic citizens. Given humans are about 60% water, it makes sense that staying alive requires adequate hydration. But that’s the big picture.
The physiological functions (e.g. Popkin et al., 2011) of water range from thermoregulation, such as sweating to digestion, such as preventing constipation; kidney function, where water is required to filter waste from the bloodstream into urine; and it is essential for neurotransmitter production (e.g., Mustafayeva, 2025) and synaptic communication in the brain.
How hydration benefits brain health
The last item is closely linked to psychological functioning, as neurotransmitters (e.g., Sheffler et al., 2023) are involved in mood, sleep, cognition, appetite, and motivation. Good hydration, therefore, is essential to mental health. Also, just being near water has positive psychological effects, but more on that later.
While some people can be so dehydrated they became delirious or develop significant cognitive impairments, most people experience more benign, but nonetheless performance-impairing effects of dehydration at times. In fact, researchers Trinies et al. (2016) tell us that there is a well-established link between hydration and improved cognitive performance. For example, exercise-induced dehydration has been shown to negatively impact memory, attention and visuospatial function. Also, children who drank more water have been recorded as performing better on tests of memory and attention (e.g. Edmonds, 2012).
Other researchers such as Haghighatdoost et al. (2018) found that lower daily water intake has been associated with increased risk of depression and anxiety. This was backed by an earlier study by Pross et al. (2014) who reported that when people who drank high volumes of water decreased their intake, they reported feeling less calm, content and vigorous, and a decrease in positive emotions. The reverse was found in people who increased their water consumption.
One hypothesis as to the water-mood link is that dehydration increases the stresshormone cortisol. Kashi et al. (2025) noted that people who drank less than 1.2 liters of water per day had higher serum cortisol levels than people who drank 2-4 liters. An increase in cortisol can contribute to irritability, anger, appetite and sleep disturbances. Hence, one may feel moody if they become dehydrated, like one might feel “hangry” when they have not eaten for some time.
How much water is optimal?
This of course will vary, but it’s recommended that, in general, adult females consume 2.7 liters and adult males 3.7 liters of water per day (e.g. Seal et al., 2022; Faizan & Rouster, 2023). I’ve heard a lot of people say they don’t meet that requirement because, “I’m not thirsty,” but that’s hollow logic. When you’re thirsty, you’re already dehydrated. Further, maybe you do drink a lot of water, but nonetheless still feel thirsty, and thus are dehydrated. The culprits can range from underlying medical conditions like diabetes to excess caffeine consumption and medication side effects.
The take-home is that dehydration is a physical and psychological stressor. If you’re not a water drinker and experience brain fog, fatigue, moodiness, and/or anxiety, the remedy might be a trendy water bottle away. For those prone to anxiety and mood-related disorders who don’t prioritize water consumption, dehydration could be exacerbating your symptoms.
On the flip side, there is such a thing as drinking too much water. According to the National Kidney Foundation (2023), this can lead to dangerously diluted sodium and potassium levels, called hypernatremia. It is sometimes referred to as “water intoxication”. Hypernatremia can cause anything from headaches to neuropsychiatric conditions. When I worked in a jail, there was an inmate who drank an inordinate amount of water for some reason. When I met with him, he was so disorganized that he was speaking “word salad” and physically uncoordinated.
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Of course, checking with your doctor about increasing water intake is a good idea, as it could negatively affect some medical conditions like edema.
Look at the water, lower your stress?
Speaking of water’s role in stress reduction, it’s not only by consumption. While it is well-documented that being in nature has significant stress-reducing effects (e.g. Stott et al., 2024; Li et al., 2025), researchers have been finding that merely looking at water has salutary effects. For example, researchers Coss and Keller (2022) reported that average blood pressure and heart rate decreased and relaxation increased when subjects were looking at water.
For those interested in a deeper understanding of how and why being near or in the water makes you feel good, marine biologist Wallace Nichols wrote: Blue Mind: The Surprising Science That Shows How Being Near, In, On, or Under Water Can Make You Happier, Healthier, More Connected, and Better at What You Do.
Disclaimer: The material provided in this post is for informational purposes only and is not intended to diagnose, treat, or prevent any illness in readers or people they know. The information should not replace personalized care or intervention from an individual’s provider or formal supervision if you’re a practitioner or student.
Coss, R.G. & Keller, C.M. (2022). Transient decreases in blood pressure and heart rate with increased subjective level of relaxation while viewing water compared with adjacent ground. Journal of Environmental Psychology,81.https://doi.org/10.1016/j.jenvp.2022.101794.
Edmonds, C.J. (2012). The effect of water consumption on cognitive performance. Appetite (59)2, 624. doi: 10.1016/j.appet.2012.05.056
Faizan, U., & Rouster, A.S. (updated 2023, August 28). Nutrition and hydration requirements in children and adults. In: StatPearls. StatPearls Publishing. Retrieved July 7, 2026 from https://www.ncbi.nlm.nih.gov/sites/books/NBK562207/
Haghighatdoost, F., Feizi, A., Esmaillzadeh, A., Rashidi-Pourfard, N., Keshteli, A.H., Roohafza, H., & Adibi, P. (2018). Drinking plain water is associated with decreased risk of depression and anxiety in adults: Results from a large cross-sectional study. <a href="https://absafricatv.com/fifa-world-cup-2026-diary-spains-final-triumph-day-40-in-ny/” title=”FIFA World Cup 2026 Diary: Spain's Final Triumph, Day 40 in NY”>World Journal of Psychiatry,8(3), 88-96. doi: 10.5498/wjp.v8.i3.88
Kashi, D.S., Hunter, M., Edwards, J.P., Zemdegs, J., Lourenco, J., Cecile-Mille, A., Perrier, E.T., Dolci, A., & Walsh, N.P. (2025). Habitual fluid intake and hydration status influence cortisol reactivity to acute psychosocial stress. Journal of Applied Physiology, 139(3), 698-708. doi: 10.1152/japplphysiol.00408.2025.
Li, Y., Mao, Y., Mandle, L., Rydstrom, A., Remme, R.P., Lan, X., Wu, T., Song, C., Lu, Y., Nadeau, K.C., Meyer-Lindenberg, A., Daily, G.C., & Guerry, A.D. (2025). Acute mental health benefits of urban nature. Nature Cities,2, 720–731. https://doi.org/10.1038/s44284-025-00286-y
Mustafayeva, L. (2025). The Effect of Hydration and Dehydration on Cognitive Performance and Mental Health. In: Mohamed, W., & Özge, A. (eds) Feeding the Mind: The Connection Between Diet, Drugs, and Mental Health(Volume 1). Springer, Singapore. https://doi.org/10.1007/978-981-95-1414-4_15
National Kidney Foundation (2023, November 1). Hyponatremia (low sodium level in the blood).Kidney.org. https://www.kidney.org/kidney-topics/hyponatremia-low-sodium-level-blood
Popkin, B.M., D’Anci, K.E., & Rosenberg, I.H. (2010). Water, hydration, and health. Nutrition Reviews, 68(8), 439-58. doi: 10.1111/j.1753-4887.2010.00304.x.
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Stott, D., Forde, D., Sharma, C., Deutsch, J.M., Bruneau, M. Jr., Nasser, J.A., Vitolins, M.Z., & Milliron, B.J. (2024). Interactions with nature, good for the mind and body: A narrative review. International Journal Environmental Research and Public Health, 21(3):329. doi: 10.3390/ijerph21030329
Trinies, V., Chard, A.N., Mateo, T., & Freeman, M.C. (2016). Effects of water provision and hydration on cognitive function among primary-school pupils in Zambia: A randomized trial. PLoS One, 11(3). doi: 10.1371/journal.pone.0150071.
