A fascinating question, a fascinating result and a poor study

Using Ecological Momentary Assessment to Determine Media Use by Individuals With and Without Major Depressive Disorder
http://archpedi.ama-assn.org/cgi/content/full/165/4/360

Small sample size, crappy counting, poor reliability of diagnosis, lack of seeing the opportunity of digital for research (though I think the boys might not have been happy with the researchers knowing how much porn they look at), measurement of race as white or non-white, the whole internet as a discrete category of media (it's a conduit) and a few other complaints are why I reckon this isn't a great study.

However...it uses a novel research technique: Ecological Momentary Assessment  It's sort of like an annoying partner ringing up every so often to find out what the subjects were doing. In this case the annoying partner was a researcher who could contact the subjects at the weekend to find out what media they were using at the time.

The question is great but more research is necessary: is their a causal relationship between media consumption (here media includes electronic entertainment, for example computer games) and mental illness (specifically depression and depression with anxiety in this study).

The author's conclusions...well...I'm not sure.
"
Despite its limitations, this study provides valuable insight into potential associations of media exposure with MDD. In particular, it lends additional support to previous theoretical concepts and empirical studies linking MDD with increased popular music use and decreased print media use. Although this study helps clarify some of the theoretical relationships of our conceptual model, it also suggests the need to further elucidate the directionality and strength of those relationships. Determining the potential role of media use in the development or perpetuation of MDD may lead to interventions designed to better screen for and prevent MDD.
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