New York magazine reached out to several sleep and stress experts to explain why it is that mental fatigue can feel so… physical.

Dr. Steven Feinsilver, the director of sleep medicine at Lenox Hill Hospital, stresses that mental fatigue is very much legitimate. He explains that the human body reacts to stress in many of the same ways regardless of whether the source is mental, like a difficult math problem, or physical, like running.

Get the full story at nymag.com