Not Facebook per se but I'd say social media in general contributes to anxiety, jitteriness, shortened attention spans and depression. The barrage of "likes" and "follows" and other ego ticklers is addictive in the extreme. The worst side of people usually comes out and folks that may be meek in their private lives become obnoxious a...holes on social media. I try to avoid it as much as I can - but I'm not very successful at it. As for FB - I use it only professionally, so it's much less toxic for me than Twitter and Instagram