I think caffeine has a different effect on each person. I know people who will be anxious all day if they drink a single cup of coffee, and others who won't feel anything after 8 cups.
I also find that there is a lot of contradictory information about coffee over the internet. There is so many studies about the benefits of drinking coffee, it's almost suspicious, and when you look for it there is also a lot of studies showing it's not healthy. However, everyone seem to agree that green tea is good for your health.
I think the best way to go about caffeine is by observing the reaction of your own body.
What I've personally observed is that coffee, for me, does work as an antidepressant on the short term. On the long term (one coffee everyday for more than a month), it gives me brain fog, increases SA and makes me feel crappy in general.
Green tea or black tea has no negative effect on me though, but you don't have the temporary rush that coffee gives. So it doesn't work for me as an antidepressant, but green tea makes me feel more healthy on the long term. Didn't really noticed anything with black tea.
I probably sound very serious about that matter, but I have a love/hate relationship with coffee, so I did a lot of research, lol