"Winter is coming!" is the fearful catch-cry of TV series Game of Thrones. And historically, there's good reason to be afraid. In ancient communities, the months following the winter solstice were famine months. While starvation may not be something to fear in contemporary Australia, the season can have a profound effect on our well-being, influencing our mood, mental health, hormones, fertility, brain function and activity levels.
We're now in the depths of what demographers call "the season of death", meaning you are more likely to die in winter than in any other season. Death rates in Australia are higher by an average of 20 per cent in the months of June, July and August compared with the monthly average, according to McCrindle Research.
Come winter, the number of people contemplating solutions to mental-health problems appears to rise. A study conducted between 2006 and 2010 found the number of people in the US and Australia searching the internet for specific mental-health terms was higher in winter. In summer, search queries within Australia for the term "suicide" dropped by 29 per cent compared with winter searches. Using the same time-period comparison, searches for "schizophrenia" fell by 36 per cent, "bipolar" by 17 per cent, eating disorders by 42 per cent and obsessive-compulsive disorder by 15 per cent.
Blood pressure is more likely to rise in winter because blood vessels narrow in cold temperatures. Feeling cold may also trigger the fight/flight response, increasing the heart rate. This combination is a problem for people with serious cardiovascular and respiratory health problems.
Winter marks flu season, and viruses and respiratory illnesses increase. A popular theory is that indoor heating dries out nasal passages making it easier for viruses to enter our system. The colder temperatures also favour the survival of viruses: Research by the National Institutes of Health in the US found that temperatures around freezing point are beneficial to the membrane of viruses, enabling them to survive longer and to be transmitted from person to person.
And winter darkness has a mental toll in the form of seasonal affective disorder (SAD), also known as winter depression.
If this all sounds a little grim, take cheer from the following: your brain is sharper and more productive on those gloomy, cold days of winter. A study published in the Journal of Experimental Psychology found people had superior memory recall on cold, cloudy days compared to bright, sunny days. Likewise, a study by Harvard Business School found productivity to be higher on days when the weather is "bad", because people are less distracted by recreational possibilities outside work.
And although winter is typically the time we put on weight, studies suggest we could harness the winter cold to lose it. This might involve turning the heating down. Research published in Obesity Reviews indicates that obesity may be related to indoor heating. Maintaining body heat when cold requires burning energy, a task indoor heating negates.
It's called non-shivering thermogenesis, whereby cooler weather generates fat-burning tissue called brown fat (which is better than the white variety).
And research shows male fertility is at its peak in winter with men producing healthier and greater numbers of sperm. Therefore, winter seems like a good time for making babies or knuckling down to work. For those wanting to lose weight, turn off the heating and fast - not feast - for a slim winter bod.
Above all, stay optimistic. Spring is just around the corner.