A writing addiction?

Another writer friend, Don Monkerud, wonders if there aren't any

"drugs to treat this writing desire. It would help us out tremendously... anyone who can escape this need to isolate oneself in a room and write for hours--toward what end, I keep asking myself--can go on and lead a productive life."

I suppose there isn't any one thing that drives us to write. For me, it's no longer about fame and fortune; I don't expect either (though I won't get out of their way if they come after me). Partly, I do it for the same reason as García Márquez: "So my friends will love me better." That's why I put things up on my blog, to imagine myself in a dialogue (it becomes a real dialogue when somebody answers me, which happens, but rarely). The main reason, though, must be just that I have to try to understand what's going on, including what's going on in my own head. I make journal entries that I don't expect ever to look at again, because the process of writing is itself enough for me to work out some problem. Also I do it for practice: try to describe something, say the dappled water tanks on the roofs I see outside my window, each a barrel of vertical rough wood slats, crowned with a 16-paneled Chinese coolie's hat, against a background curtain of horizontal courses of black and russet brick. Efforts like these are like finger exercises on a guitar or piano. Or maybe more like batting practice, because it's a matter of hand-eye coordination. And why do it? Mainly for the satisfaction of doing it a little better each time, and in the hopes of getting to strut my stuff before a wider audience.