A look into some ideas that cause people to be depressed

Hey friends!

I have long thought about what it is that drives our human condition. One of the things that is very prominent in our world right now is it seems that so many people are depressed and I think a lot about theories as to why this might be.

Whereas I think that depression is caused by a myriad of things such as diet, not enough time with nature things of that sort; the one theory that always comes back to me is that it's related to how quickly our lives evolved on a technology scale when our physical selves did not evolve at the same rate.

What's this mean? Well basically, I think we came from the womb, got handed a phone and thrown on to a computer and handed a meal in 15 seconds through a window while our bodies will want to connect to nature, and hunt for our food.

The fight or flight response demands a reaction from our sympathetic and parasympathetic nervous systems. Situations cause for adrenaline to build up in our bodies in preparation for a survival function. The world we live in today isn't crawling with animal predators that we have to protect ourselves from or work for our food, everything comes quite easily if we want it to. If you think about that on a grander scale, we have a race of people designed for great physical exertion and power that really has no use for those functions.

So my question to you is, do we store adrenaline without ever really needing to expel it from our bodies? Does the lack of needing to fight to survive cause us to depressed? Is nature one of the keys to feeling better? Following along that train of thought, would expelling excess adrenaline by means of exercise or extreme sports do the trick?
What are your thoughts?