During winter when the nights are long and days short, getting up for work in the dark and coming home in the dark can be grim. Some of us succumb to the January blues, leading to increased illness, reduced productivity and a general feeling of melancholy. But can clever lighting improve our sleep patterns and lift our moods? "I only feel like I start to breathe properly again after the solstice," says Jacqueline Hazelton, a professor at the US Naval War College in Rhode Island. She's referring to the winter solstice - usually 21 December - the point after which the days start lengthening again following the longest night of the year.