“While this has been posited many times, though, it’s still embryonic research,” says Allsobrook. “The effects of caffeine on ADHD still need to be thoroughly investigated to draw more firm conclusions.”

Caffeine dehydrates you

Finally, have you ever noticed that caffeine makes you feel dehydrated and makes you need the loo? That’s because caffeine is a proven dehydrator and a diuretic, meaning it helps get rid of the body’s water content.

This is an instant ticket to sleepiness. As Steph Norman, founder of Norlo Coffee, explains: “As the body loses water, the body’s blood volume decreases, which results in less overall oxygen being distributed around the body. Less oxygen now equals more exhaustion and feelings of tiredness and fatigue.”

Caffeine is also a vasoconstrictor, says Steph: “It makes blood vessels smaller and slows blood flow, further amplifying the blood flow issues resulting from the diuretic properties of caffeine which, again, makes us feel more tired.”

Can coffee make you sleepy? Here’s why you might have a caffeine slump