Does Twitter have a word filter that censors some words?

[Lissy]

I'm a new user, but I just noticed earlier that topics like "Diarrhea" were trending (After reading a few posts, it seems to be beacause the pop star Justin Bieber had diarrhea thrown on him... Which is awful).
An hour later or so, I got some bad news and thought it might be nice to lick my wounds, so I typed in the search bar "sad", my results showed maybe 1 every hour or so. "Depressed" was the same.
Do they filter those results? I know I can't be the only person feeling this way at the same time as others?
What's going on?
Not saying that's accurate, this is only my first experience with Twitter. It could be some dumb piece of gossip.
I just don't know what to trust from it though. I'm a newb.. :-P

[Sarita]

I cant find any article saying that justin bieber had diarrhea thrown on him.