Hydration and ADHD
Genevieve Mackenzie, PhD
We talk about routines, sleep, structure, coaching, and medication when it comes to ADHD.
But we often overlook something far simpler—something so quiet most people barely consider it:
Water.
Hydration is one of the gentlest, most accessible ways to support an ADHD brain. And research shows its effects ripple through attention, working memory, energy, and emotional regulation. For children and adults alike, even mild dehydration can cloud the mind more than we realize.
Below is what science tells us—and why water deserves a place in every ADHD toolkit.
Why Hydration Matters for the ADHD Brain
Water fuels nearly every cognitive function:
memory, attention, emotional regulation, and processing speed.
For neurodivergent brains—already working harder to filter information, manage impulses, and stay focused—hydration becomes a form of support, almost like cushioning for the gears of executive function.
Several studies across schools, labs, and classrooms point to the same truth:
when children or adults drink water, cognitive performance improves.
1. Water Boosts Visual Attention and Focus
A foundational study from the University of Westminster found that children ages 7–9 who drank water before completing cognitive tasks performed significantly better on visual attention tests (Edmonds & Burford, 2009). They also felt less thirsty—a small shift that translated into big cognitive gains.
Younger children showed similar improvements. Kids aged 6–7 demonstrated sharper visual search and better attention after drinking water (Edmonds & Jeffes, 2009).
For ADHD, where distractibility and visual tracking can be daily challenges, this matters.
2. Mild Dehydration Is More Common Than We Think
In a study from Sardinia—one of the hottest climates in Europe—84% of schoolchildren arrived at class mildly dehydrated (Fadda et al., 2012; Bar-David et al., 2005).
Dehydration wasn’t dramatic.
No sweating. No sports. No heatstroke.
Just ordinary, everyday mild dryness.
When these students drank extra water, they showed improvements in:
short-term memory
verbal reasoning
overall fatigue
For kids with ADHD—who often struggle with working memory—the findings are especially important.
3. Working Memory Improves After Drinking Water
Working memory is the mental workspace that helps us:
follow instructions
hold information long enough to use it
regulate emotions
stay organized
It’s one of the core executive function challenges in ADHD.
Multiple studies show that working memory rises reliably with hydration:
Water improved digit-span and visual cancellation tasks (Perry et al., 2015).
Adults performed better on both verbal and spatial working memory tasks within 20 minutes of drinking 300 ml of water (Edmonds et al., 2022).
Long-term memory did not change—but the mental clarity needed for moment-to-moment tasks noticeably sharpened.
4. Hydration Helps When Attention Needs to Last
Some research found that while initial test scores didn’t drastically change, the second round of attention tasks showed improvement when students had water (Krecar et al., 2014).
This suggests hydration helps with:
stamina
sustained attention
cognitive endurance
Exactly the areas where ADHD brains often fatigue first.
5. Stimulant Medications May Increase Vulnerability to Dehydration
Stimulants like methylphenidate and amphetamine increase dopamine and norepinephrine—but they also slightly raise heart rate and metabolic demand. Some people sweat more. Some urinate more. Many eat less, which lowers fluid intake.
Although dehydration isn’t officially listed as a common side effect, clinicians note a pattern:
children on stimulants may drift into mild dehydration without realizing it (Martin & Hammerness, 2014).
Especially if caffeine is involved.
Especially in warm weather.
Especially during activity.
Water can help stabilize energy, reduce headaches, and support cognitive steadiness throughout the medication cycle.
Creating a Hydration Ritual for ADHD
Hydration works best not as a single drink but as a rhythm—woven into the day with intention.
Try:
A glass of water first thing in the morning
A refillable bottle on the desk
Sips before recess or movement breaks
A drink before homework
Extra water during physical activity
Small habits become anchors.
And anchors build regulation.
Water Won’t Rewrite ADHD—But It Can Steady the Mind
Hydration won’t replace therapy, coaching, medication, or structure.
But it supports them—all of them.
Water nourishes the nervous system.
It steadies the noise.
It softens the edges of overwhelm.
And sometimes, it gives just enough clarity to change the shape of the day.
For a brain that runs fast, feels deeply, and thinks in sparks, hydration is a simple act of care with a quiet power all its own.
References
Bar-David, Y., Urkin, J., & Kozminsky, E. (2005). The effect of voluntary dehydration on cognitive functions of elementary school children. Acta Paediatrica, 94(11), 1667–1673.
Edmonds, C. J., & Burford, D. (2009). Should children drink more water? The effects of drinking water on cognition in children. Appetite, 52(3), 776–779.
Edmonds, C. J., & Jeffes, B. (2009). Does having a drink help you think? 6–7-year-old children show improvements in cognitive performance from baseline to test after having a drink of water. Appetite, 53(3), 469–472.
Edmonds, C. J., Beeley, J., Rizzo, I., Booth, P., & Gardner, M. (2022). Drinking water enhances cognitive performance: Positive effects on working memory but not long-term memory. Journal of Cognitive Enhancement, 6(1), 67–73.
Fadda, R., Rapinett, G., Grathwohl, D., Parisi, M., Fanari, R., Calò, C. M., & Schmitt, J. (2012). Effects of drinking supplementary water at school on cognitive performance in children. Appetite, 59(3), 730–737.
Katz, A. I., Massry, S. G., Agomn, J. L., & Toor, M. (1965). The role of the kidney in water metabolism. The American Journal of Cardiology, 15(1), 77–84.
Krecar, I. M., Kolega, M., & Kunac, S. F. (2014). The effects of drinking water on attention. Procedia – Social and Behavioral Sciences, 159, 577–583.
Martin Jr., E. B., & Hammerness, P. G. (2014). ADHD, stimulant medication, and dehydration. CHADD.org. Retrieved from https://chadd.org
Perry III, C. S., Rapinett, G., Glaser, N. S., & Ghetti, S. (2015). Hydration status moderates the effects of drinking water on children’s cognitive performance. Appetite, 95, 520–527.