What is the medical term for sad mood?

What's the word for that persistently sad feeling? You know, that low-level blah that just... hangs around? Dysthymia, apparently. That's the fancy medical term. And honestly? It sounds brutal. Just brutal. I mean, imagine feeling down, not just for a day or two, but for months, maybe even years. It's like having a low-grade, constant ache in your soul, right? Sometimes it gets worse, like a storm on top of an already dreary day, but it's always there. It's not just in your head, either; I remember reading somewhere – maybe it was a magazine article, or maybe a friend told me, I can't quite recall – that it messes with your sleep, your appetite, even your energy levels. It's total body bummer. My aunt suffered from something similar, though they never diagnosed her specifically with dysthymia. She just always seemed…tired. Drained. Like the light was always off, you know? Ugh, just thinking about it makes me feel a little down. Seriously, it sounds exhausting.