Does Thinking Hard Makes You Feel Tired? Researchers Explain Why This Happens

Researchers explain why thinking hard makes you feel worn out, and what can you do when you experience mental fatigue.

Getting tired after performing some hard physical work or a long workout at the gym is normal. But do you know that thinking hard also wears you out? This is the reason why you feel exhausted even when you're not doing any physical labor but were just sitting thinking hard for hours. Like hard physical labor, hard mental labor makes you tired.

Surprisingly, the reason for tiredness from intense thinking isn't all in your head, according to a new study reported in Current Biology.

The authors explained that when you're engaged in intense cognitive work for long hours, toxic byproducts tend to build up in the prefrontal cortex, the part of the brain that plays key role in cognitive control functions. This alters your control over decisions and makes you stop working to preserve the integrity of brain functioning when cognitive fatigue sets in.

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The findings contradict popular theories that suggest "fatigue is illusion cooked up by the brain to make us stop whatever we are doing and turn to a more gratifying activity" the researchers noted.

What can you do when you experience mental fatigue?

Why understand why thinking hard leads to tiredness, Mathias Pessiglione of Piti -Salp tri re University in Paris, France, and colleagues monitor the brain chemistry of people whose work require thinking hard as well as those who had relatively easier cognitive tasks, using magnetic resonance spectroscopy (MRS).

Only those doing hard work showed signs of fatigue, including reduced pupil dilation. The researchers also found higher levels of glutamate in synapses of their brain's prefrontal cortex. Moreover, their choices shifted toward options proposing rewards at short delay with little effort. This, according to the experts, proves that glutamate accumulation makes cognitive control more difficult after a mentally tough workday.

How to get rid of mental fatigue? Simply take rest and sleep, Pessiglione said, adding that sleep helps eliminate glutamate from synapses.

Don't make important decisions when you're tired, Pessiglione advises people.

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