Health and online activity are inextricably linked at this point.
Mental health. Cardiovascular health. Health of interpersonal relationships. Work life balance.
I sincerely think we are at an equivalent situation as the tobacco industry in the 1970s. The decisions we make now will affect the lives of generations to come.
Cal Newport's site has a Ledger of Harms [1] at the Center for Humane Technology, and I wrote what I hope is an accessible and lightly challenging overview of the problem of technology overuse in Digital Vegan [2].