During my time in college and (protestant) seminary (7 years in all) I have had a number of classes that dealt with psychology and the behavioral sciences. I also have taken a number of classes in history. There is an interesting place where these two disciplines intersect. If we examine the perspective on mental problems in the past and in the modern times, we find a very clear change in perspective; and it is not for the better.
In the modern world the majority of people perceive mental problems as coming not from our own influence but from something more inoffensive. Family, job, health, money, or housing problems are no longer considered to be a reason for feeling down or defeated. If you are depressed today, the claim seems always to be that you have a chemical imbalance. It seems the vast majority are unwilling to consider any personal behaviors or decisions that can impact a person's depression. Thus, doctors give a pill for sadness rather than encourage them to learn how to deal with sadness. Taking a pill because you have a "condition" that was not your fault is much easier to accept than being told you made a bad choice and are accountable to deal with the consequences.
If we examine the biblical testimony about our minds and hearts, and compare that with the modern knowledge about mental illness, we find the two do not fit together very well. The Scriptures blame our bad circumstances on our bad choices. Most of those bad choices come from a selfish motivation; we want something wrongfully, we pursue something wrongfully, or we acquire something wrongfully, and then results come from it; results which we are unwilling to accept.
In actuality, not only the testimony of Scripture, but common experience shows us that fixing a (supposed) chemical imbalance does not change a person's heart, and will therefore not change his behavior. It is our spiritual state that drives our decisions in life and it is therefore that spiritual dimension that has the greatest influence on whether we are depressed or not. The problem with accepting the spiritual dimension of modern man's depression is that pharmaceutical companies do not make any money from spiritual problems, because there is no pill for it. You have to go to a spiritual expert (i.e. an orthodox Catholic priest) to deal with spiritual problems.
This is not to ignore those who do have true mental issues that stem from actual physical infirmities but merely to note that those are not as common as we are made to believe. If, someday, our society turns back to recognizing the real root of the vast majority of our emotional and mental problems, we will find great blessings. In the mean time, let us make sure that we do not merely blindly follow the world's prescription for wellness. Trust me, giving more money to a pharmaceutical company does not heal any spiritual malady.