Yes and yes.
Let me give you a true example.
When I was a young child a very traumatic even occurred.
I always knew it happened, but with time I was able to push it down when it came into my mind. (not healthy but that's what I did as I did not have access to help -or even know I needed help as a child).
I grew up, married, had children.
When my daughter reached the age in which I was traumatized, I started experiencing nightmares, extreme reactivity, extreme fear, dropped out of my social life, and I was in no way able to control or push down the thoughts of the traumatic event.
I ended up getting help (because I seriously thought I was losing my mind). I was diagnosed with PTSD.
Since I had not had an opportunity to receive any type of help dealing with or processing the traumatic event as a child I had been "shoving it down". The triggering event to the PTSD becoming uncontrollable was my daughter reaching that age. My fear that it would happen to her, made my own trauma come roaring to the surface.
With time and counseling (2yrs) I was finally able to process and move beyond the traumatic event.
In fact, I realized that a lot of things I did in my daily life prior to counseling, most that could be seen as "quirks", were in reality very much connected to the trauma.
I can't really give a lot of examples without letting out more than I am comfortable with about the trauma, but many could seem to a "quirks" but actually were because of a sense of being unsafe. One small example, no matter where I was I always had to sleep on the side of the bed farthest from the door. I never realized it was always the farthest from the door, just thought I was "quirky" that I had a definite side of the bed but it flip flopped depending on where I was.
Depression is often situation and will clear up after whatever issue (divorce, job issue, illness, etc) is resolved. Unless it is a clinical depression, which is an actual brain chemical imbalance which will not go away on it's own and needs to be managed with medication.
Hope that helps.