This is simply false -- the literature is full of discussion about the health effects of social media.

More generally you're committing I believe two separate fallacies of ambiguity? Like one in going from the institution of social media to its reification in the form of specific websites, and then a second fallacy when you go from the specific websites to all websites in general? Like if you said "Gun ownership is not a thing at all. Gun ownership is a piece of metal. Pieces of metal cannot be healthy or unhealthy." OK but, you owning a gun is known in the scientific literature to significantly correlated with a bunch of very adverse health effects for you, such as you dying by suicide or you dying from spousal violence or your protracted grief and wasting away because your child accidentally killed themselves. Like to say that it's impossible for the institution to have adverse health effects because we can situate the objects of that institution into a broader category which doesn't sound so harmful, is frankly messed up.

[1]: Bernadette & Headley-Johnson, "The Impact of Social Media on Health Behaviors, a Systematic Review" (2025) https://pmc.ncbi.nlm.nih.gov/articles/PMC12608964/ - the content you consume can promote healthy or unhealthy behaviors

[2]: Lledo & Alvarez-Galvez, "Prevalence of Health Misinformation on Social Media: Systematic Review" (2021) https://www.jmir.org/2021/1/E17187/ is notable not just for its content but also like a thousand papers that cite it getting into all of the weeds of health influencers sharing misinformation to make a buck

[3]: Sun & Chao, "Exploring the influence of excessive social media use on academic performance through media multitasking and attention problems" (2024) https://link.springer.com/article/10.1007/s10639-024-12811-y was a study of a reasonably large cohort showing correlations between social media usage and particular forms of multitasking that inhibit academic performance -- more generally there's broad anecdata that the current "endless scrolling constant dopamine hits" model that social media gravitates to, produces kids that are "out of control" with aggressive and attentional difficulties -- see Kazmi et al. "Effects of Excessive Social Media Use on Neurotransmitter Levels and Mental Health" (2025) (PDF warning - https://www.researchgate.net/profile/Sharique-Ahmad-2/public...) for more on the actual literature that has probed those questions

[4]: The APA has a whole "Health advisory on social media use in adolesence" https://www.apa.org/topics/social-media-internet/health-advi... which is pretty even-handed about "these parts of social media are acceptable, those parts can maybe even be downright good -- but here are the papers that say that for adolescents, it can mess with their sleep, it can expose them to cyberhate content that measurably promotes anxiety and depression, it has been measured to promote disordered eating if they use it for social comparison..."

Online age verification is the hill to die on