Increased Water Intake Improves Sleep/Wake Cycle and Mood

Most of us probably hardly pay any attention to how much water we drink per day. And while you may have heard that drinking more water is good for your health, little is known about how water intake affects us, especially our mood? A study by French researchers that explored the effects of changes in water intake on mood state found that increasing water intake can improve one’s overall mood whereas reducing water intake has the opposite effect.

Image: Free Digital Photos

Image: Free Digital Photos

In this inpatient study consisting of 52 participants, habitually high-volume drinkers (who normally drank more than 2.5 liters of water per day) were restricted to drinking less than 1 liter a day and at the same time low-volume drinkers (less than 1 liter of water per day) increased their intake to more than 2.5 liters a day for three days. During the three days, participants in the two groups had the same meals as well as sleep and wake hours. They self-reported their mood states using several scales—which included tension, depression, anger, fatigue, confusion, and calmness among others—five times a day.

Unlike most previous studies that only measured the mood effects within an hour of water intake, the current study measured the effects over a period of three days.

At the beginning of the study the mood states of both groups of drinkers were mostly comparable. Upon reducing their water intake, the high-volume drinkers felt overall negative effects; they reported a decrease in calmness, contentedness, vigor, and positive emotions. In contrast, the low-volume drinkers experienced less fatigue, confusion, and sleepiness after increasing their water intake.

This study suggests that habitually low-volume water drinkers can boost their sleep/wake mood by simply increasing their water intake. But the authors said that the mood-worsening effects observed among habitually high-volume drinkers cannot be generalized because all the participants in that group were female, who may be more sensitive to water deprivation.

Nevertheless, this study shows how the simple habit of water-drinking has a significant impact on our moods and sleep—at least more than we would have thought. So whenever you are thirsty, consider a glass of water instead of soda or other energy drinks.


Pross N, Demazières A, Girard N, Barnouin R, Metzger D, et al. (2014) Effects of Changes in Water Intake on Mood of High and Low Drinkers. PLoS ONE 9(4): e94754. doi:10.1371/journal.pone.0094754


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