Is “Depression” Real?

Question by Anthony N: Is “Depression” Real?
I rarely watch television, but whenever I am “lucky” enough to I also manage to run into one or two commercials regarding depression and its alleged symptoms. Now, from what I believe, depression is just a state of sadness caused for whatever reason, but I looked at a dictionary definition and I found two related descriptions from Wiktionary:

“2 (psychology) in psychotherapy and psychiatry, a state of mind producing serious, long-term lowering of enjoyment of life or inability to visualize a happy future
3 (psychology) in psychotherapy and psychiatry, a period of unhappiness or low morale which lasts longer than several weeks and may include ideation of self-inflicted injury or suicide”

Now I am no doctor nor do I claim to have much medical or psychological experience, but why has depression become some sort of sickness? Are people just not able to be happy for whatever reason? Is this a case of technical definitions gone too far?

A direct answer is not necessary; any information is welcomed.

Best answer:

Know better? Leave your own answer in the comments!