I don't quite believe depression to be an Illness rather I think it's the effect of a habit developed overtime and here is why.. human beings tend to experience negative emotions like sadness, anxiety, jealously, anger, hatred etc because of the WAY IN WHICH THEY PROCESS EVENTS that occur around them. Now when a person continues to process things in a manner that causes them to feel negative emotions, they inevitably manifest the effects of these emotions. So a person feeling angry will lash out and act erratically so too a person that constantly CHOOSES to think in a way that makes them to feel sad will end up manifesting depression... and the solution to this so ridiculously simple one only needs to ask themselves "HOW CAN I?" rather than "WHY ME?"