Speaking from personal experience, depression definitely forced me to face my problems and thoroughly analyze them. The focus depression generates is pretty impressive, even the things I'd distract myself with would often take on the feeling of a search for a missing puzzle piece, like the key to making sense of all my sorrows was just out of reach.
Shifting ones mental perspective is not trivial, and probably essential for overcoming certain types of depressions. In the end I was finally able to notice the blind spot in my mind that I'd been avoiding, and from there take a different path that led me to peace and happiness. It took a lot of effort and insight to get to that point so I for one firmly believe depression has its uses.
I second that experience. However, somewhere in the multidimensional spectrum that constitutes depression, there is a cliff where people can fall (for a variety of reasons, or in case of organic causes, for no apparent reason at all) into a deep cycle of clinical depression. That type of depression is characterized by a horrible crippling effect which prevents sufferers literally from accomplishing anything, including changing their lives for the better.
I'd even go so far as to say that clinical depression is probably over-diagnosed in cases where there are clear external reasons for the person having a crisis. Sometimes, having a crisis can be a perfectly normal and even "healthy" response to events. Though it is a bitter experience, it can even be productive, as you described. But at a certain point, when people fall of the previously mentioned cliff, the brain chemistry can change and make them prone to devastating episodes that are rightfully characterized as a disease.
The Ashkenazi are a fascinating case study for this subject. We still don't know whether a tendency towards being depressive is a biochemical tradeoff for heightened mental capabilities, or whether intelligence makes people miserable because it allows them to see the nature of reality more clearly. Maybe high intelligence and a sarcastic sense of realism about the world correlates with depression because it's the only logical response to the way the world works.
Is there really a higher incidence of depression among the Askenazi? I hadn't heard that before. I can see how German or European Jews would have been affected, possibly for generations after WWII, but that set does not include all Ashkenazis, and definitely includes some Sephardics.
I'd agree - depression does force you to see that something is off-kilter and needs changing - but I've found that it doesn't place you in a mindset that makes it easy to see what is wrong, how to fix it, or how to go about identifying those things. Much of that can be learned so perhaps it's a shift in treatment that's called for (along the lines of cognitive therapy, which I have found beneficial, as well as meditation + yoga, which I have found even more beneficial).
However, I've also learned 'do not make major life decisions while depressed' because often depression lurches to radical and likely long-term damaging solutions which may have a short-term benefit of short-circuiting the depression (e.g. thinking 'quit job immediately without having another one lined up and having family depending on the income').
Shifting ones mental perspective is not trivial, and probably essential for overcoming certain types of depressions. In the end I was finally able to notice the blind spot in my mind that I'd been avoiding, and from there take a different path that led me to peace and happiness. It took a lot of effort and insight to get to that point so I for one firmly believe depression has its uses.