Quite a few papers from the last 6 years or so which suggest that with certain intake limits caffeine has many beneficial and few harmful effects.

Look at the paper by Poole, Kennedy et al on the benefits or Morales-Brown.

The accepted wisdom that coffee is bad for you is slowly being challenged and the orthodoxy changed to it having benefits rather than being neutral.

4 cups a day seems to be well within ‘safe’ limits .

Whilst it is a stimulant it is not hugely addictive with no cravings etc outside of a 24 to 48 hour window. Habituatuon means you should have days with lower consumption if you want to get the full benefits later.

A lot of critics have been converted by some of the new evidence - eg Prof Tim Spector.

Caffeine intake is hard to isolate to test it by itself as you can’t just consume caffeine. Historically, a lot of the research seems to have failed to exclude the effect of other foods or habits such as smoking.

Like anything some people will be more or less affected (I have mates who don’t drink caffeine in any form after midday) and some people may have conditions a or risk factors than mean they need to be very careful but for the rest of us - time for another cup….