Subtitles section Play video Print subtitles On average, Americans spend 87% of their time indoors. But what if you ditched that last bit and gave up the great outdoors for good? Odds are you've been stuck at home before, maybe because of bad weather. Maybe there's a pandemic and you're self-quarantining. You probably wouldn't notice a huge difference at first, other than a bit of cabin fever. But after a week and a half, things may start to change. Ironically, after spending all that time indoors, you may start to feel tired, no matter how much sleep you get. You see, being stuck inside limits the amount of sunlight you get. Normally, when sunlight hits your eyes, it signals to your brain to stop producing a hormone called melatonin, and that hormone affects your circadian rhythm, which regulates sleep. Without a reliable sunlight trigger, your body will just keep making melatonin, and it might start to feel tired all the time. Sunlight is also a trigger for your body to produce serotonin, aka the happy hormone. It helps to regulate your mood, among other things. So without enough sunlight, after a few months, your melatonin levels will rise, and your serotonin levels? Those may drop, along with your mood. It's this combination of decreased sunlight and serotonin that's credited as one of the main causes of seasonal affective disorder, or SAD. It's a type of depression that is most prevalent during long, dark months. SAD is relatively uncommon, but it may increase if we all stay locked in our homes. You may be thinking you can just bring in artificial sunlight, like a light box. Well, this has been shown to reduce the effects of SAD, but not cure it. And it wouldn't really matter, because your mood can be affected by another important factor. The great outdoors. Just being outside in general has been linked to lower stress levels. So say goodbye to staying calm, and hello to higher blood pressure. Plus, that inside air is stale. The Environmental Protection Agency says it's up to five times more polluted than the air outdoors. This isn't good news for your lungs. Over time, breathing in that recycled air could increase your risk for illnesses linked to pollution. And four months to a year down the road, your body is going to start missing something vital to your health: vitamin D. This is essential for optimal health, bone strength, and muscular regulation. In order to make vitamin D active, you need sunlight, and artificial won't do. When ultraviolet B rays hit cholesterol in your skin, energy is released, and that fuels the production of vitamin D. Without that production, though, your vitamin D levels will start to drop. And if you don't do anything to counter this decrease, you might find yourself losing strength or getting depressed, while your bones gradually become weaker. Vitamin D is also important for regulating your immune system, so you could be at a higher risk of catching illnesses, too. The next development is a little hard to predict, since vitamin D levels vary from person to person. But you may start seeing some very serious issues in a few years. Lower levels of vitamin D could put you at a higher risk of developing heart disease or strokes, plus an increased risk of cancers, fractured bones, and serious tooth decay. Years down the road, you might feel some pains, specifically in your bones and hips. You could even have difficulty walking, finding yourself waddling or swaying precariously. Now, vitamin D supplements may or may not help replenish that loss of activated vitamin D. But even with that help, you might struggle from a lack of mental stimulation. In other words, you'll be bored. The monotony of everyday life in the same place doing the same things over and over again, without stepping outdoors... that may all start to take a toll. If you don't have to go outside, you're likely to become more sedentary, meaning you'll exercise less. And research has shown that even a short 12-minute walk can reduce symptoms of depression and help you cope with stress. This could be worse if you live by yourself. Social isolation and loneliness have been linked to conditions like high blood pressure, heart disease, anxiety, and depression. And if you're quarantined, you could be dealing with a range of psychological stressors, resulting in undesirable symptoms like low mood and irritability, along with insomnia and depression, all made worse by the fact that you'll be inside day after day doing the same thing. So maybe, if you can, go and take a walk outside. And if you can't, well, try staying active. Open a window to let fresh air in. Find ways to bring more sunlight into your home so you don't mess up your sleep schedule. It also wouldn't hurt to form a support system to keep you connected with the outside world. Set up video chats or call your family and friends. Others might be going through a similar experience, and bonding over it could be validating, giving you what you need to get through.