I had lunch with an author friend recently, and she mentioned that her editor has twice now commented on the mood of her books, which gets darker in bad times and lighter in better times. The editor has never met my friend but accurately identified times when she was dealing with personal tragedy. The books were different than those which came when life was happily humming along.
Wow. Do we know we're revealing so much of ourselves as we write?
I know from studying literature that great authors' works often grow darker as life buffets them around a bit. Twain got much more satirical after the deaths of his wife and daughter. Shakespeare wrote more tragedies as he aged.
What happens to a mystery writer when life takes a downturn? We already write about murder and mayhem, so what can get worse? Apparently, it's the mood of the writing, the sense that maybe life isn't fair after all. The mental condition of the protagonist can change, too. He or she might not expect justice, or at least not full justice.
In case you're thinking of analyzing me, you should know that I wrote for almost ten years before anyone noticed. Some things just now coming to publication were written years ago; others are being written in the present day, with all its attendant troubles. I can't see much difference, though I've had plenty of ups and downs over that time.
It must be considered that an author's mood might have an opposite effect on her writing. If life tramples us into the dirt and we long for happiness, fairness, and justice, we might simply create it where we can, in our books.