Dehydration corrupts mood on healthy adults in the long run.  

Dehydration occurs when the body losses too much liquid. It can be mild, moderate, or severe. A severe case of dehydration is an emergency, and it can lead to death. The human body can lose a high amount of liquid because of:

• Excessive sweating like exercising in a hot climate.
• Fever.
• Vomit or diarrhea.
• Urinating too much (uncontrolled diabetes or some medication like diuretics can provoke a person to urinate a lot).

Children and older people are the most vulnerable to dehydration. In children, gastrointestinal diseases can lead to dehydration. Generally, the only cognitive sign of dehydration observed in children is diminished physical activity and/or somnolence. In older people, mental confusion, irritability, and somnolence are signs of dehydration.

A study on mild dehydration in healthy volunteers during daily activities, evaluated memory, awareness, speed of processing, and mood. Results showed that levels of dehydration affected man and women differently. Changes in cognitive performance were low between sexes; women showed a variety of adverse changes in mood, like fatigue,  headaches and problems focusing, while man did not show any change.

This suggests, according to researchers, that women are more sensitive to the effects of dehydration. This is sustained by other group of researched, where in a study, they evaluated the effects of severe liquid restriction in mood and cognition of young healthy women. Results showed that fluid privation had harmful effects on mood that were observable only after a few hours of liquid deprivation. An increase of somnolence and fatigue was observed, as well as an awareness decrease and confusion, though it did not affect other cognitive functions. Cognitive performance such as attention, memory, awareness, etc.), was not affected, even after more than 20 hours of liquid deprivation.

The effects of rehydration were also measured. It was showed that most mood alterations were reverted by just an intake of water, but it did not improve fatigue and strength after water intake. This indicates that a 24 hours deprivation of liquids can have effects on mood on the long run.

Mild dehydration in adults can constantly worsen mood and it is characterized by somnolence and a substantial decay of well-being. When dehydration is induced just by liquid deprivation, healthy adults are capable of keeping performance, but in older people, studies showed that mild dehydration affects cognitive performance, like in children.

Symptoms of dehydration can vary according to age:

In adults, excessive thirst, urinating less and in a dark brown color, fever, fatigue, dizziness, and confusion.

Causes can be: diarrhea or vomit, fever, excessive sweating and a constant need to urinate.

Reviewers: Brenda Giselle Álvarez Rodríguez (Public Health Research Unit) and Cassandra Saldaña Pineda (Knowledge Management Unit).

Sources:

• Article: “Effects of Dehydration on Brain Functioning: A Life-Span Perspective”. Ann Nutr Metab 2017;70(suppl 1):30-36
• Mayo Foundation for Medical Education and Research
• MedlinePlus