Bright future: Sweden's light therapy school
For people living near the Arctic Circle, winter means enduring long, dark nights and as little as two hours of sun each day.
This can have wide-ranging effects from depression, to disturbed sleep, obesity and even cancer.
But now two projects in Sweden are trying to brighten things up.
Sweden's first "light therapy" school, in the northern town of Umea, has installed full spectrum lighting that teachers hope will improve results.
And the Swedish Healthy Homes project is testing a more personalised approach to ensuring that citizens receive the right dose of sunlight.
Malcolm Brabant reports.