hi missceamypie,

you need to be by your mum's side whenever she's depressed. do not judge and do not ask her "not to think so much" (though this is the tendency for most ppl to advise depressed souls).

it is not their choice that they think too much ... being depressed it's not a choice either and depressed cannot help but be depressed for whatever reasons there are. as someone who knows the depressed victim, you just need to lend them your ears and heart because it is at this moment that they need someone whom they trust to listen to them and possibly console them.

try to understand what's causing her to be so depressed helps. most ppl who are depressed just want to release their tensed feelings to ease themselves... so listening and caring and understanding is the best help you can offer them