So what can we learn from this example? I would suggest at least three lessons:
The cure for the depression Cain experienced is obvious from the causes, isn't it? All Cain had to do was confess his sin and ask for God's grace. But he refused to do so.
We can also learn from Cain's example that sometimes depression is a signal of pride and unresolved sin in a person's life. Sadly, most people today resent even the suggestion of this possibility when they seek help with depression. Yet, isn't this the very issue God Himself raised with Cain in response to his depression? Indeed it is, and it is the very issue many who struggle with depression need to confront in themselves as well. In fact, although I risk sounding insensitive to many, and even cruel to some, when I say this, nevertheless I must say that in my experience some of the most depressed people I have known are also some of the most prideful or angry people I have known. I include my own past struggles with depression in this assessment.
Now, I would of course never say that this is the only – or even the primary – reason for depression for many who struggle with it, but I do believe it is a far more common source of depression than many want to admit. And the reason they don't want to admit it is the very same reason that Cain didn't want to admit it, because they would rather blame God or some other person for their dilemma than take responsibility for themselves. This tendency toward refusal to take personal responsibility for one's actions or the state of one's own heart is a growing problem in our culture, and it has made significant inroads into the churches as well.
In addition, even where unresolved sin such as pride and anger are not readily identifiable as the source of one's struggle with depression, these sins are often present as a response to depression. I have dealt with many a person who responded to their struggle with depression by becoming angry at God, for example, and who have pridefully refused to let go of their anger, and it has only made their battle with depression even more difficult.
Therefore it is all the more important that we do not shirk from raising the issue of sin when dealing with depressed people. Although we may not know their hearts the way God knew Cain's heart, we do know that they were born sinners just as Cain was, and thus we also know that sin will likely be a crucial factor in their struggle with depression, whether as its source or as a complicating factor.