While you are currently able to prevent posts with certain tags appearing on the feed, there doesn't seem to be an option to hide all posts marked with "adult content".
I think this already happens if you say you are under 18 on registering, but sometimes people over 18 just don't want adult content sometimes too.
Thanks and Merry Eggbug,
You can find this under "Settings -> Display Settings -> What posts you see -> hide adult content behind a clickthrough", unless you mean you would like them to be completely removed from your feed.
Yeah I mean completely remove from the feed.