Depression like most matters has many causes and reasons and no one approach of counselling/therapy has the complete picture.
Some models propose that depression is repressed anger and the inability to allow anger/rage and shame with appropriate expression.
Buddhism suggests that it is a loss of heart and courage to face the trials of life.
The existential school might consider depression a loss of meaning and purpose and without meaning depression expresses itself as a sense of meaningless.
Other models propose that we are depressed because we don't think right.
Jung's work proposes a loss of soul and therefore a loss of adequate spirituality and most scientific circles consider Depression as a matter solely of the chemistry of the brain.
All are valid for depression- the flattening of feelings and its hopelessness etc are a world wide issue.
There are depression scales and tests which can be used to assess one's level of Depression and they are freely available on the internet.
I have suffered from reactionary depression from time to time and it is always a call to go within and learn the lessons of Depression.
Depression speaks to us through its symptoms and we need to learn the language of our symptoms and not just merely medicate them away. Many are aware of the problems with antidepressants yet they too have a place.
Enter into a relationship with your Depression be creative and playful, sit with it -running away will increase depression, medication solely will numb the soul, and in my opinion and experience- Depression is a matter of the soul's heart not being listened to.
We are depressed in a world full of depressing things and this is a realistic perspective for the Depressive is not wrong about their view of themselves in situ with the world.
Depression is much more than low self esteem- this animal makes a bad master when we try to be positive while affirming that the negative feelings, emotions,thoughts and behavious are ignored, for these thing are talking to us.
The sickness hold the cure within its very nature like it or not.
There are a plethora of things one can do with Depression and again they are valid but few counsellors/psychologists et al know how to plumb the depth of Depression- the current paradigm is that Depression is bad and it must be gotten rid of at all costs but Depression doesn't go away so easily does it.
Depression is neither good or bad it is what it is and most people know its call.
Where we fail is in heeding and responding to its call- it will always call for us to really look at our lives and find the way out of this Darkness.
A good article to find on the internet comes from www.jrhaule.net and his article called Depression and soul-loss.
When our lives are depressed its fundamental call is to say that the ways in which we live are failing us.
How then do we live when we seem to be failing in many aspects of our lives- that's the question Depression wants to answer?