New study of 1,787 adults ages between 19 and 32, finds a significant relationship between depression and social media usage. Specifically, the more social media someone uses the more likely it is that they suffer from depression even after controlling for relevant covariates.
http://www.ncbi.nlm.nih.gov/pubmed/26783723
http://www.ncbi.nlm.nih.gov/pubmed/26783723