Have you heard of Wim Hof, 'The Iceman'? He's been on the Joe Rogan and Tim Ferriss podcasts recently. He's known for his amazing ability to not only withstand cold, but to use his breathing techniques and mind-mastery to control his own immune response. Pretty bad-ass. You can watch a documentary about him on Vice. His courses are now booked months in advance. He just held his first one in LA, a sure sign of his massive popularity. Everyone in the human potential movement LOVES the cold! Tony Robbins and Dave Asprey (of Bulletproof coffee fame) both use cryotherapy (chambers that get you very cold, very fast with no frostbite!) as part of their bio-hacking efforts.
Dr. Jack Kruse calls it cold thermogenesis (CT). The benefits of CT range from improved fertility to weight loss, pain reduction to better blood sugar levels and increasing immune function. Apparently going out in the cold won't give you a cold like your Grandma said, but will make you thin and immune to viruses. Who knew?!
For most of history humans were exposed to the cold on a regular or semi-regular basis. This goes in the 'duh' category. It explains why we came up with clothes and shelter. Even though we are known as the hairless ape, we are still adapted to the cold and it carries benefits. Our current exposure to 68 degrees fahrenheit almost constantly (via our insulated buildings) isn't creating a lot of adaptation pressure, and we don't seem to do well when we make life too cushy. We get fat, unhealthy, slow and dull-witted. Please see the movie Idiocracy for more information on this.
We've been more exposed to the cold in 1 month living in our second-skin (canvas, pop-up home) than any other time in our lives. It's Spring in the mountains, so the weather vacillates wildly from 80 degrees and sunny to sleeting and 48 degrees with howling wind. When the temperature drops, we do what humans have done for a long time; find shelter and layer clothes (blankets, sleeping bags) to simulate fur. Moving from the bedroom to kitchen exposes us to the cold, it takes longer to warm up at night and a trip to the restroom requires a jacket. These small exposures have changed our behavior. We sit closer to each other while watching movies (hey, we aren't trying to re-create the past here!), cuddle more (ahem, in addition to more serious cuddle time between Jon and I) and rely on each other more in some very small ways.
If we design buildings, and then they design us (Winston Churchill's famous quote) consider this: A warm house (while super nice!) does not require you to get next to your fellow human beings to get warm. This is a behavior that is so normal in the animal kingdom, but mostly lost to modern, Western (i.e. rich) humans. A recent very chilly night prompted me to seek extra warmth with my mate (luckily he is a large, heavily muscled specimen who generates a lot of body heat). I haven't spent the whole night cuddling with someone maybe ever? I woke up in the best mood possible, just brimming with good feelings. There is a ton of research about skin-to-skin touch and how it raises oxytocin levels. Oxytocin is our mammalian bonding hormone and it promotes attachment, reduces stress hormones, boosts sexual hormones, triggers protective instincts and helps people sleep.
You don't need to ditch your house or sleep in the snow to get more cuddle time and the big benefits of oxytocin. Turn your heat down at night, leave a window open, sleep with less blankets, go camping more and turn to your people for warmth. And no, it doesn't have to be a sexual partner, cuddling with kiddos is awesome and important bonding time. Additionally, cuddling with friends and siblings is completely normal and accepted in many societies all over the world. We ('Mericans) are one of the least touching groups of people in the world and it isn't good for us.
In whatever way you can, exposing yourself to varying temperatures is good for your metabolism, endocrine system, sex life and your mental health. We didn't become what we are by insulating ourselves from natural pressures. Withstanding the cold (or heat) creates some mental toughness and a flexibility that can only benefit the user. The creativity involved in finding solutions to varying temps, and body awareness (where you start to know your own limits) are other important benefits. So get cold (showers, baths, swimming) or hot (sauna, steam, hot yoga) and let your body adapt, allow your mind grow stronger and use those varying temps to create stronger bonds between you and your loved ones.
Cold Therapy - http://www.mensfitness.com/training/pro-tips/benefits-of-cold-therapy
How To CT - https://www.jackkruse.com/cold-thermogenesis-easy-start-guide/
Wim Hof - http://www.icemanwimhof.com/innerfire