Disclaimer: The following article is based on personal experience with depression (your experience may differ if you've had it or have it) and some past research. When I make generalizations, I'm correlating my experiences with my research. It is not an all inclusive guide nor is all of the information exclusive to depression. Some can pertain to other disorders as well.
Causes
You seem to have this figured out, but you need to understand that a single tragic event isn't the only cause of depression. It can be, sure. The death of a loved one or another kind of loss can certainly cause it, but sometimes it's not nearly that simple. Depression can be the result of a single large event, a barrage of large events (domino effect) or a lot of small ones over an extended period. What causes the initial sink is going to vary from person to person. And of course, what causes depression in one person is overcome by another.
Depression can happen to anyone. Even those who appear to have it all in life can be depressed.
The Large Event
Loss – This is broad. It can be the death of a loved one, a pet, the loss of a job, having either you or someone you love become permanently injured, the onset of a disease, the break up of a long-term relationship or divorce, childbirth (some women view it as a loss of freedom), losing a custody battle, loss of a parent's love in legitimate cases of abuse and neglect, etc. Anything you can think of that would constitute a serious loss in a person's life fits here and could easily be a trigger for depression.
The Domino Effect
When it Rains, it Pours – Sometimes shit happens in life. We all deal with things that go wrong. Unfortunately, sometimes major loss events happen in close succession. What some call a spot of bad luck is really disaster for others. I would refer to this as a loss of control; when a situation gets completely out of hand and you can do nothing but let it spiral.
The Little Things
They Add Up Fast –Now the definition of "little things" is going to vary between people. For some it can be as simple as a parent or family member forgetting their birthday, not picking them up at school, or missing their dance recital. Seemingly little mistakes can turn into an overall feeling of neglect if they keep happening. For others, it can be a case of favoritism. Perhaps your best friend seems to be favored by the coach of your sports team? Maybe your little brother seems to be the favorite of your parents and could probably get away with murder if he wanted to? Or maybe it's that overwhelming feeling that no matter what you do, the universe is conspiring against you? Whatever it is, that "little thing" isn't so insignificant to the person experiencing it. And sometimes, it compounds.
What Does it Feel Like?
A lot of people would define depression as a constant, overwhelming feeling of sadness, but really, it's so much more than that. There's a reason it's so common and so hard to overcome.
The first thing to know is that depression is cyclic. Everyone has their day to day ups and downs but for people who are depressed, those downs may be more significant to them, and more frequent, than their ups. As an example, the feelings of depression can last for several years, and then something really good might happen to lift your character out, and he may be happy again for a while, years even, but eventually depression comes creeping back again. The cycles are different for everyone of course. Some may only last a few days while others last for weeks or months.
So, what does depression feel like? Well, there's not a single word that can really sum it up because depression is a bombardment of many different feelings, symptoms and attitudes at once. When you're depressed, you may experience some or all of these.
