For both factors, addictiveness and harm, there are large piles of scientific studies.
Apart from magnitude of harm, I don't think it's a stretch to think that social media should be grouped together with tobacco as something we want to limit as a society. There might even be an argument on magnitude given that social media causes loneliness and loneliness causes early death https://press.aarp.org/2016-12-07-AARP-Foundation-Draws-Atte.... While I'm not saying that using facebook reduces your lifespan by 15 years, I think there is cause to assume a real physiological impact.
Sure, social media has had its positive impact - every new technology is mixed - but certainly, we need to find common-sense ways to regulate social media to reduce addictiveness and harm.