Does coffee increase anxiety? What research has been done on this subject?
There's a lot of studies/articles, but when it comes down to it it's just like any other "drug": it affects each person differently. I drink almost a pot a day, and have since I was around 17/18, and have no worsened conditions if I don't consume coffee. Some months I go with only a cup a day, and others its ~3-4 cups - and nothing changes drastically. As with anything else, especially "drugs", moderation is key.
This is, of course, anecdotal, so...
I think coffee can not increase anxiety but if you drink too much coffee, probably, you have been in a busy time. This means the stress of your life can increase anxiety. It's not related with coffee. However some people does not consider all the parameters related to their stress. Because they're used to their life and may judge the other stuff.
I only have anecdotal evidence. For me, coffee produces anxiety at first, until I acclimatize to a regular amount. For me, that's 2-4 cups a day. My body adjusts to that new "normal". I also exercise off any nervous edge coffee gives me.
In any case, I don't think coffee ever eases anxiety, even after you acclimatize. However, as a person with a tendency to be anxious, I can tell you regular exercise certainly does ease anxiety!