I've seen studies saying things either way but from personal experience it has always been weird to me that friends will literally not be themselves until they have their coffee and they are completely addicted to it and their entire morning revolves around it. If it was booze or weed or something people would say they have a problem.

But this drug is normalized in society so you'll see a line of 40 grumpy, twitchy people in the morning waiting for their fix and people dont bat an eye. A lot of people who drink coffee drink wayyy too much for it to be healthy as well.

>A 250 mg dose of caffeine has been shown to reduce resting cerebral blood flow (CBF) between 22% and 30%

That's a few cups of coffee

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2748160/

Also the teeth staining/sensitivity isn't great either