@Chrome I think you are being to harsh on @SarahA, most of the points she made will not have statistical evidence behind them, and this forum has never been about vigorous and evidence-laden arguments anyway. If you have an argument or statistical evidence to the contrary, then provide it, but merely shouting  at every point she makes just ruins the debate.
I like how sarah draws a distinction between 'depression' as a mental illness and 'sadness' or 'anxiety' individual instances of negative emotions, and I like how she ties our post-materialist developed society as a reason that people worry more and appreciate less. However, I think she fails in identifying the nature of the diagnosing of mental illnesses as socially dependent, by which I mean that mental illness doesn't really exist in an objective sense like other diseases do. If I want to know if you have the plague, I can test your blood to see if you are infected with the bacteria Yersinia Pestis, and objectively prove that this is the case. If I want to know if you 'have' depression, I have to ask you about your subjective experiences, and judge whether those experiences are having a detrimental impact on your life (which is a subjective criteria dependent upon what you consider to be a 'normal' life, and therefore based on a subjective opinion informed by a myriad of ideologies and values and social norms and economic processes). This is why I think the language that surrounds mental illness is misguided, it treats depression as a kind of disease which you either 'have' or 'don't have', when in fact our emotional well being and personal outlook on life is so immensely complex and multifaceted it is irreducible to simple categories like 'depression'. I think people who feel like their emotional well-being is having a damaging impact on their lives should be thought of not in terms of illnesses and spoke of in pathological language but in social/lifestyle terms, a depressed person is someone whose lifestyle choices, social patterns and circumstances are inadequate in allowing them to feel happy and fulfilled; and thus needs to make changes to those patterns. I think it makes sense that first world kids with no issues surrounding food, shelter, work, clothing, education and other basic rights are going to care a hell of a lot more about whether their lifestyles are making them as happy and fulfilled as they can be, I think that explains the massive spike in mental health issues, and I think that's a good thing. I'm not trying to devalue mental illness, on the contrary, I think the recognition of this fact can help people overcome depression.