“The best thing people should do,” he says, “is get out at lunchtime. There’s a lot of evidence that the light you get in the evening is less important than the dose of bright light you got at lunchtime. And it gives you exercise and makes you feel better.”
“If you go back in time,” says O’Hagan, “as soon as the sun went down you went to bed, and got back up again when the sun came up. It isn’t natural to extend your day with artificial lighting. People are also doing activities in the evenings they wouldn’t have done even 20 or 30 years ago and that stimulation may be having far more effect than the light itself.”