1) Being on social media releases a chemical in the brain that give happiness, which is addictive.
2) When a person looks completely calm, while on the inside, their anxiety is raging.
3) It increases anxiety and major depressive disorder, along with other disorders like eating disorders and Bulimia.
4) While they can be useful, they do more harm than good, mainly because of fake news and lack of privacy.
I hope I helped. :)