I view a tendency toward depression, when it has lasted for years, as a chronic condition that can often be managed, but probably seldom cured.

I agree with you that depression probably has it's roots in the past experience of the sufferer. I'm not a big believer in the chemical-imbalance-of-the-brain school of thought. But I would disagree with you that it is a matter of unresolved emotional conflict that can become resolved by the sufferer gaining insight through insight-oriented psychotherapy.

That view was the most popular one for quite a while. It has fallen out of vogue for good reason. Not too many people got "cured" of depression that way. I remember when books would "claim" that people did get cured, but I'm not reading that lately. I'm sure most human beings are walking around psychic conflict. I don't believe that ever does get resolved. I believe we - all of us - die with emotional conflict churning away in our psyches - unresolved.

People who don't get depressed are not necessarily less conflicted than those who do. For whatever reason, their conflict does not make them depressed. Unresolved emotional conflict is one of many of life's stressors. People who tend to get depressed do so, I believe, in response to numerous stressors. One study showed that depressives score higher on reality testing than non-depressives. This study found that optimists with sunny dispositions tend to score lower on reality testing than do depressives.

I think there is something profoundly wrong with the theory that you can "logic" your way out of depression. Believing that you can do that is what underlies the theory you espouse. I disagree. The truth is there is an awful lot, objectively, that is tragic about life. Some people are more mindful of that than others.