0556.2 Assessment
Research Question (Clear, unambiguous) "[W]hether the social use of Internet is associated with increases in adolescent depression."  The description of the research question suffers from vagueness and ambiguity.  Asking in a general sense if the amount of time spent using social media is related to the amount or severity of depression symptoms (which is what the vague wordings seem to imply) among adolescents is simply to general of a question to be meaningful.  Peoples' emotional states are as much an influence on their use of social media as the reverse.  Also, beyond some extreme behavioral differences, the time spent on social media cannot tell us much without knowing how that time is spent.  Social media are not all the same. 
Relevant Literature Relying on two articles that are 20 years old for a topic that is highly dependent on current technology is not really workable.
Causal Interpretations (clear, all parts defined, mechanisms, controls, plausible) The brief discussion of causal connection ignores social media use.  The causal discussion should focus on the causes that the research is supposed to investigate, even when it is posing alternatives.
Data (variables, sample, comparison) The NLSY seems appropriate for the research as defined.  However, while you might find that adolescents with higher depression symptoms spend more or less time using social media, it is not clear that you can develop the data analysis to the point that you could make sense of such findings.  
Research Value If you could find a way to examine how social media use compared to local networks seems to distinguish outcomes for those showing depressive symptoms at some earlier age, it would certainly be worthwhile.  The project description does not show that the ideas are sufficiently developed along these lines and it is questionable whether the data would support this effort.
Overall A worthy general question, but doubtful specification and research plan.