[psychphysic]

Yes this is the biggest misconception about depression.

The idea that it is synonymous with feeling "down" and more or less depression is just how "down" you feel.

Depression is much more than just that feeling. And not all unpleasant feelings are pathological.

So the question becomes, why is it in modern times people no long feel able to say "I feel down" or "I don't like winter". Instead they need to wrap it in a medical term that appears unsupported by evidence.