I made a note about Blask's 2005 work below, which is the main work I was thinking about. We can say that constant light is bad for cancer.
But as I'm refreshing my memory, winter can cut both ways. For some, it makes more darkness and more melatonin (which is thought to be protective of cancer). For others, winter results in not seeing enough light, and so melatonin amplitude goes down. And so this is associated with increased cancer.
But as I'm refreshing my memory, winter can cut both ways. For some, it makes more darkness and more melatonin (which is thought to be protective of cancer). For others, winter results in not seeing enough light, and so melatonin amplitude goes down. And so this is associated with increased cancer.