I've been there. The best thing you can do is talk to him, hopefully you're quite close to him? I found him reading my blog (which is about depression), which was quite unsettling, but later text him to say I wish you hadn't done that. Thankfully I trust him a lot, so I knew he wouldn't tell anyone; do you trust this friend? As it's in quotation marks, is he not really a friend?
Personally, I'd hope he wouldn't tell no matter how good a friend he is- I see it as something that no-one would really be interested in and therefore not make good gossip. That's just me however! Hope nothing too bad happens!