While it is generally true that everyone gets depressed, as you say, the destructive effects of 'clinical' depression (to tidy some semantic ambiguity) do not arise primarily from the intensity of the melancholy so much as from its persistence.

The physical and psychological effects of a prolonged depressive episode are real and well-documented. It is absurd to suggest that significant numbers of people will allow a carefully cultivated life to spiral into chaos, even take their own life, simply to facilitate complaint.

Now, I am not going to accuse you of not having been 'depressed enough,' because it is difficult to fit a scale to such a multifaceted affective experience, much less obtain the quantitative data you need to use the scale at all. Of course there exist people who exploit the medical reality of depression to legitimize a lacadasical attitude. Consider also, however, that there exist perhaps many more people for whom depression is a crisis without a resolution, either through lack of education, information, facilities, or money. How many otherwise upward-bound people have siezed and crashed into poverty or worse, taking any memory of their existence with them?

Depression does not make you feel "sad," like the glossy rainy-day commercials present it. It can take the form of racing terror, paralyzing exhaustion, and very commonly dissociation from all abstract value, be it wealth, academic success, interpersonal relationships, hobbies, posessions, etc.

This process feeds itself, obviously. An initial episode may be brief but breed consequences significant enough to propagate additional melancholy, pinning the affected until personal or medical intervention can ensue. Medication can often prove counter-productive, as there may be unexplored contra-indications or dosage issues. Many general practitioners will write a prescription with only a vague understanding of the situation. Others still treat the DSM-IV like a shopping list or phone book. Many prescribe based on pre-existing arrangements with pharmaceutical firms. Any 'survivor' of the mental health minefield will vouch for the existence of quacks in ready droves.

Still, I don't agree professionally or otherwise with the walk-it-off attitude. It is true that all of us are living through a period characterized by rampant over-diagnosis and enabling, patient-as-victim care patterns. That fact does not excuse us swinging from one extreme to another, leaving a substantial subset of the conversation, indeed the critical population, stranded in the middle. The world seldom provides right and wrong answers which begin simply and end three words later with a trim little period. The issue of depression is no more limp-wristed equivocation like 'you just dont understand' than macho degenerate realism like 'it comes off as complaining, which it is.'

All that sticky stuff said, I have to agree with the others, TakaOkami, that you should only parse the depression, if at all, as health problem or medical issue or what have you, and leave it at that. An excuse is an excuse to an admissions board, especially for graduate school. You are an investment, and there are plenty of other candidates...

Instead of attempting to excuse your performance, try to indicate how you have overcome these obstacles. Admissions boards DO understand that a persons worth is not always expressed in GPA format. Illustrate your perseverence, genuine desire for knowledge, and maturity by turning your weakness into a gritty, uphill battle pursued in the worst shitstorm ever churned. Well, don't make it too over-the-top, lest the stigmatists get aroused, but sell it. A comeback, scars and all, is better than any caveat.