If you’re one of those people who can’t start your day until you’ve had that first cup of coffee — you’re doing it wrong. You shouldn’t have coffee right after you wake up, because that’s when your body is producing more of the stress hormone cortisol, and that makes caffeine less effective.

Studies have shown the average person’s cortisol levels peak between 8:00 and 9:00 in the morning. Cortisol prevents caffeine from doing its thing.

So you should get to work and then have your first cup of coffee. Or if you wake up really early, wait an hour.

There are actually three times in the day when your cortisol levels peak — right after you wake up, between noon and 1:00 PM, and between 5:30 and 6:30 PM. So you shouldn’t have coffee then either.

The good news is you can just keep doing what you’re doing, and ignore all this if you want to. Drinking coffee right after you wake up won’t kill you.

Drinking it while your cortisol levels are up does make you more likely to become addicted to caffeine. Because you’ll start needing more and more of it to feel the effects.