Laurie Clarke, on Wired:

For the small subsection of the population who experience full-blown seasonal affective disorder (SAD), it’s even worse – winter blues mutate into something far more debilitating. Sufferers experience hypersomnia, low mood and a pervasive sense of futility during the bleaker months. SAD notwithstanding, depression is more widely reported during winter, suicide rates increase, and productivity in the workplace drops during January and February.

A study looking at three pre-industrial societies – that is those without alarm clocks, smartphones and nine-to-five working hours – in South America and Africa found that these communities collectively snoozed for about an hour longer during winter. Given these communities are located in equatorial regions, this effect could be even more pronounced in the northern hemisphere where winters are colder and darker.

Before moving to Europe, I lived a good part of my life very close to the Equator line, so I had the vague idea how this could affect people’s minds. Now I see it in practice. Winter shakes the whole thing out of us and requires us to act on some matters: from using house lamps that simulate sunlight to taking vitamin D and melatonin pills.