I suffer from depression, I had a complete breakdown seventeen years ago, I was hospitlised for three months, and off work for nearly a year, so I know the difference!
I have a problem with the condition being called 'depression', simply because it confuses people - thinking that 'depression' and being 'depressed' are one and the same - as RATTER15 does. Put it this way - if being depressed is a sprained ankle, then depression is having your leg cut off with a rusty tin lid - honestly, the different is that wide.
Being depressed is part of the human condition. We all have times, maybe a day or two, when we feel a little bit fed up, but it passes. Everyone has it, it's natural.
Depression is a severe mental illness where the sufferer looses all sense of self and purpose. Simple tasks like making tea, crossing a road, bathing, and so on become beyond him. His mind races constantly, going over and over issues that distress and upset him, with no apparent rest or solution. This takes huge amounts of energy, so he will be lethargic when awake, and sleep for very long periods. The condition can be so hard to bear that death becomes an attractive alternative, hence the suicides of a lot of sufferers.
Treatment involves diagonisng particular type of depression - 'clinical' depression is the mind's response to a lack of certain chemicals produced in the brain - this can be balanced by replacing the chemicals artifically by means of medication. 'Reactive' depression is caused by a serious mental trauma, when the brain defends itself by shutting down and refusing to deal with anything evern remotely taxing. This is usually treated by professional counselling.
A person suffering from depression can often be the last to know, because it's part of the illness to loose the ability to think about yourself, and others, rationally, so the symptoms are usually notivced by fridns and family first.