Thanks, Alex, but do we know there is a lower incidence of depression in third world countries, or do we know there is a lower incidence of REPORTED depression? The fact is, when you have to struggle every day to put food on the table, are you going to go and complain to the doctor that you are depressed? Besides, the rather 'direct' way of living which many people in poor areas are forced to live, does not allow 'depressed' behaviours such as lying aorund on the couch all day. Also, even if people in third world countries ARE less depressed, I don't think a causal link between mass media and depression has been established. There could be many, many more factors at work here.
The nursing home study is interesting, but again it shows no causal link between watching tv and getting depressed. Some people (like, for example, women) are more prone to depression than others, and perhaps these people might be more inclined to watch TV because of that or other personality traits. What came first, the personality or the TV?
Either way, though, I do think many of us watch way too much TV. It may or may not cause depression, or trigger it or exacerbate it or whatever, but life is short and there may be better things to do with our time. Like reading.... 
