On the great depression

I'm depressed. Like as many as one in ten other people, I know I'm depressed. The fact is, because I know I know, I can carry on as normal knowing why.
Depression is one of those things that people would class as mental illness. I personally think depression is two completely separate illnesses (I'm sure Bryn would back me up here), but both with the same symptoms.
Some make reference to depression as being the black cloak. As if it's being dragged over you, everything becomes dark and lonely. I personally think that it feels like a black blood, running through you, lowering your personal feelings and making you lethargic and not wanting to move. I also believe that this isn't the depression people associate with being depressed, but more a physical reaction to a chemical or other imbalance somewhere in your body. So, it's a physical thing leading to a mental state. We all know that alcohol is a depressant. We also know (ladies) that chocolate in small doses is an anti-depressant. Maybe these things enhance or combat the unidentified chemical that leads to the depression in the first place.
The other kind of depression, which in my opinion is completely separate, is caused by external factors. The soldier who's returned from Iraq, the recently widowed, the bereaved. These are all factors that lead to depression, but not the same depression. This is a depression that is part of the mental process of healing the mind. It is not however a chemical imbalance. It is there for a reason.
One can be combatted with medicine, the other with time and love. They aren't inter-changeable, and I don't think they should be. I do, in contradiction to my own theories however, believe that they can cross into each other's paths. Someone or something upsetting you can lead to the trigger that means that a slight imbalance that went undetected now means that you are feeling the effects of the depression.
I do not however, as the great Ronnie Barker put it, "let the bastards grind you down."