Can Thinking Too Much Make You Tired

Does Thinking Tire You

Thinking and Tiredness

It isn’t uncommon to find oneself super tired after a day of performing various thinking tasks at the office, but often people assume that it is because they didn’t get enough sleep the night before or they blame it on the long commute back home. As it turns out, being tired after thinking really, really hard might literally be all in one’s head.

Thinking is Hard Work

According to Julia Wilde of, the human brain makes up only about two percent of the body’s weight but the brain uses up about 20 percent of the all of the energy one takes in. And, a study that was published in Proceedings of the National Academy of Sciences USA discovered that about two-thirds of all of the energy used in the brain goes to the “firing of cells” while the other third goes toward “brain maintenance.” (

Some scientists have speculated that when humans work on difficult mental tasks, they burn up a lot of glucose. “Most of the energy powering the brain is in the form of glucose from the things we eat,” says Wilde. “When neurons fire, they absorb extra oxygen and glucose from nearby capillaries.” So, if human burn up a lot of glucose while thinking, then it would mean a lot less of the stuff in the blood to do anything else which then leaves one with the feeling of exhaustion from “just thinking.”

Thinking with One’s Mind, Body and Soul

This theory goes along with another study performed at the Texas A&M Health Science Center School of Public Health and was published in Human Factors: The Journal of the Human Factors and Ergonomics Society. The study found that people generally felt more exhausted when they had to exert energy with both their mind and body. (Science Daily)

When people perform mental and physical tasks at the same time, they activate the prefrontal cortex of the brain. Just like any other part of the body, the brain can be overused with fatigue.

“Existing examinations of physical and mental fatigue has been limited to evaluating cardiovascular, muscular and biomechanical changes,” says Ranjana Mehta, Ph.D., an assistant professor at the school. “The purpose of this study was to use simultaneous monitoring of brain and muscle function to examine the impact on the PFC while comparing the changes in brain behavior with traditional measures of fatigue.”

The studies at Mehta’s school found that the oxygen levels in the blood of the participants in the study were lower when tracked performing both mental and physical tasks. Mehta found that the brain’s resources were divided and may have contributed to the physical fatigue.

Another study performed at the University of Kent pitted two groups against each other for 90 minutes. One group was tasked with watching a documentary about trains and Ferraris while the other had to take a mentally-challenging computer test. Then, both groups were asked to jump onto a stationary bike and peddle for a while. In every case, the documentary-watchers were able to ride their bikes longer than the test-takers. (Like Tracker)


Science Daily – – –

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Thinking process [ID 149397169 © Bulat Silvia |]

Man thinking [ID 109147026 © freephoton |]