Sure.

Well, that's just it though; They appear to be a major causal factor. They might be. But is there any reason for us to believe so, other than the observed correlation of some stressor with the onset of an episode? And even then: do they cause or trigger the illness?

Or maybe that's what you mean - that a life event triggers the episode, not that the traumatic event is the genesis of the illness?

I guess you can never definitively prove it. However, given what we know about how the stress system works, how long-term high cortisol affects the brain, etc., it's pretty well established that long-term stress has certain measurable effects on structure of the brain. Also, there have been studies showing similar changes in brain chemistry in animals to that seen in depressed patients, when put into socially stressful situations.

I'm not entirely sure what your differentiation is between "trigger" and "genesis" in this case. Can you explain?

I'm sorry, I don't think I made myself very clear:P

My point, summed up, is one regarding definition.

Maybe it's just pedantry, but I find that your use of cause (what I also describe as genesis) sort of implies that it is a progenitor - that it is a starting point of sorts.

And what I'm suggesting is that there are other factors at play (biopsychosocial model) long before the culmination of the disease in a major depressive episode - provided we are still talking about the term "depression" as in "major depressive disorder."

In the cases I have witnessed, life events have been the progenitor. There are obviously other factors, such as personality, genetics, etc. However, life events seem to have been the main "cause" of these depressive episodes (and not just the trigger).