And no, it's not right when you wake up.

A morning cup of coffee has become an integral part of the routine for so many people. It's tasty. It re-energises you. It helps you brace for whatever the day ahead has in store. Basically, it's just short of magical. But if you're one of the people that reaches for a cup of coffee first thing in the morning, we've got some bad news. Not only is it actually counterproductive, it can lead people to build a tolerance for the drug, thereby diminishing its effect down the road. This is all because our bodies create a hormone called cortisol - which is also known as the 'stress hormone', as it often appears when we are stressed out or worried. But it's also a big part of our natural hormonal cycle throughout the day, known as the circadian clock, which is what helps us wake up in the morning - and wind down at night. Basically, when our bodies release cortisol, we feel more awake. Cortisol peaks in the early mornings, which is why drinking coffee during these times is a bad idea - it interferes with cortisol production. The body then produces less of the hormone, relying on caffeine instead. And drinking our coffee while cortisol levels are high leads to the development of a longer-term tolerance for caffeine. This is why it may feel like your morning cup of coffee has less of an effect. Popular YouTube channel ASAP Science explained that it isn't all bad news (thankfully). Cortisol levels peak three times throughout the day: before 9am; between 12pm and 1pm and between 5.30pm and 6.30pm. If you want to get the most out of your cup of coffee, it is recommended you drink it between those times - so between 10am and noon and 2pm and 5pm. Makes sense.