Thanks to both of you.

No, the not-writing didn't trigger the depression. But I wondered if putting myself under that extra mental strain (of making myself write every spare second I had) might have pushed me over the edge?

It's interesting that you both say to do it.

I'm not blocked, as such. And the difficult scenes are already written (they nearly killed me).

I'm at the editing stage, which means I have to visualise the whole novel, every part, simultaneously. It's like keeping a thousand plates spinning in the air all at the same time. As soon as I start, I'll be my usual obsessive self with it. It seems like a massive act of concentration to me right now, looking at it from the outside.

It is ironic; writing helps, but hurts too.