Basically everyone who consumes caffeine is a chronic user. Everyone I know of drinks it daily, and skipping one day is very unpleasant until your brain gets used to lack of it again (a couple miserable days).
There goes HN with the health quackery again. Citation needed other than your opinion on you circle of acquaintances.
Drinking 300mg vs 50mg of caffeine a day are not the same, and lumping everyone under chronic just because you have a strong opinion on the topic is silly.
In this case they define chronic as someone who consumes over 200mg per day but the article and paper itself is very weak as they did not accurately measure subject's caffeine intake, they just went on subject's self reported data("I drank a coffee and a red bull") and built estimations on that which is weak science as there's not a fixed amount of cafeine in a cup of coffee but can vary wildly.
https://www.statista.com/chart/19524/cups-of-coffee-drunk-by...
"The average American coffee drinker drinks just over 3 cups per day."
https://www.ncausa.org/newsroom/nca-releases-atlas-of-americ...
200 mg is about two cups of coffee.
https://www.healthline.com/nutrition/how-much-caffeine-in-co...
What about those who consume it in small moderation?
Just because other people abuse it doesn't mean those who do not suffer the exact same negative effects in the same manner.
Of course studies will mostly focus on the cronic consumers as those will generally show the biggest symptoms and will be easier to study and draw conclusions versus the non coffee consumers, but that doesn't mean everyone is chronic consumer.
Not as defined in the study we are discussing, which labels "chronic consumers" those who take more than 200mg of caffeine per day.
200mg is not the highest number but the threshold they seem to define for chronic. There are definitely people who drink way more than 200mg as that's only about 2 cups of coffee. I assume heavy cafeine users go above 300mg.
Before learning about caffeine psychosis, my peak caffeine consumption was probably 8 cups/day where each cup was 2 table (not tea) spoons, so, ah, in retrospect terrifying: http://www.wolframalpha.com/input/?i=caffine%20in%2016%20tab...
I've known people who are completely unproductive if they're not on Adderall, or on cannabis, I can't think of any reason there aren't people who are entirely useless without caffeine.