Selfishness...hm, I guess it's part of the human experience. I just don't want people thinking that depression is a sin or something. If someone lost a child and got depressed, they are being selfish? Grief and trauma can cause chemical imbalances. Tragedy can cause extreme suffering, like war. IMHO, to suggest that someone who hadn't found a way to deal with their tragedy could be selfish is kinda harsh. I understand about individual experiences and all. I'd say, the average person who is depressed is not selfish but is suffering to find a way OUT of their situation and have not yet found it.
I believe there are legitimate situations that cause hurt and grief but can develop into selfishness that may lead to depression. Kind of like how anger can develop into bitterness when not checked at the door.
1. There is no condemnation in Christ Jesus. So when you sin as a christian that does not mean you are hellbound. This includes unintentional sins. A lot of our actions may be rooted in sins and we dont even realize it. Thats where grace and mercy come in. God knows our hearts so even when hurt causes us to sin unintentionally...God is a loving father that is looking to restore us not to condemn us.
2. Having said that, Im not sure that I would label all selfishness a sin. (Yall know how I am about calling stuff a sin when its not lol). I believe (personal belief) that there are times where selfishness could be a sin, where selfishness is not a sin but may be "inappropriate", and times where selfishness could be an appropriate choice.
Examples: Sin: If I see someone laid out in the middle of the street with no one else around and I simply pass them by without seeing if they need help or dialing 911 etc. cause I didnt feel like it. I think that would classify as having sinned. (It also happens to be against the law).
Inappropriate but not a sin: You want a snack. I have one but choose not to share it with you. (I probebly should share with you but I wouldn't label it a sin if I didnt)
Appropriate choice: I choose to give $35 to a charity a month even though I could afford to give $100. (And no God hasn't lead me to give anything...this was my choice). I have nothing in particular that I spend the other $65 on. Just because I haven't given ALL of my money to the poor doesn't mean I have sinned.
So when we go through traumatic situations we do have a right to mourn, cry, whatever and it doesn't necessarily mean we are being selfish. But when we fall into depression because of it we have become consumed by it and God doesnt want that for us. When we become consumed by situations we have taken our focus off of God and put it on our situation. Its not usually a conscious choice...its often gradual...but that doesnt make it any less selfish. It doesn't mean that you want to be depressed...doesnt mean that you're not trying to find a way out. Its just helpful to know the/a source.
Though I dont think all cases of depression are caused by an initial act of selfishness, I do believe that most likely all have a thread of selfishness running somewhere in them.
I know OP said she was not talking about chemical imbalances but since they were mentioned, I dont have a clear understanding of how they all work and therefore am not sure if the above applies to them. I do know this though...those of us who have experienced PMS, a chemical/hormonal imbalance, are not exempt from exhibiting self-control. We dont get a pass to wild out and have an attitude, God still expects us to be temperate (it just may take more effort and diligence at these times). So we do have power over (at least some) mental/hormonal issues, and therefore dont have to be victims of those strongholds.