I (29F) have had on and off depression for as long as I can remember and further (while my memory of it doesn't go that far back, I've seen photos of myself from when I was 10/11 with signs of self harm)

It will come in phases, and not always linked to stressful situations. The past year has been very full of life stress (work, love, relationships) and while it has been difficult I have not been depressed. However, last year, when these stresses weren't in the picture, for 5 months I was severely depressed and spent most of that time in bed, with no energy to do much else but sleep and sob.

These episodes come in phases, and when I come out of it I can't explain the feeling, it's like one day I wake up and just have the energy again and I'm up and out the door. They have lasted sometimes only a couple of weeks, sometimes will go on for months, there doesn't seem to be consistency.

I'm at a place now where I'm really trying to work through it and work out where it comes from. I have only ever tried therapy this year, but only very short term due to the expense.

Speaking with my only support person, they are of the stance that this kind of episodic depression is always rooted in something that happened. I've always rejected that approach, as as far as I can remember there have been no distinct traumatic events that have happened in my past.

I'm wondering from anyone who has a similar experience, and began the healing, is there always a traumatic root to these moods and phases? 

TLDR; is there always a traumatic root to long-term episodic depression?