>> negative consequences of facebook use
Do those "academics" also research the positive consequences as well? I'm in touch with my high school and university friends to this day thanks to FB products. I value those friendships highly, but I now live on the other side of the globe, and I can't physically be there myself. My parents (and my wife's parents) are active users of WhatsApp and Instagram. My brother (who's also on the other side of the globe) communicates with me mostly via FB Messenger. I'd say my mental well-being benefits significantly from less isolation. I'd also say there are millions of other people like me, who can still easily keep in touch in spite of vast distances separating them from relatives and old friends.
Would alternatives exist if there was no FB? They likely would. But I don't have a problem with FB, as long as it's used moderately. I my view, however, it's a personal responsibility to moderate use. Part of being a functioning adult, so to speak.