Neuroscientists kept rats in the dark for six weeks. The animals not only exhibited depressive behavior but also suffered damage in brain regions known to be underactive in humans during depression.
Further, neurons that produce norepinephrine, dopamine and serotonin, which are common neurotransmitters involved in emotion, pleasure and cognition, were observed in the process of dying. This neuronal death may be the mechanism underlying the darkness-related blues of seasonal affective disorder.
The dark-induced effects may stem from a disruption of the body’s clock. When an organism’s circadian system is not receiving normal light, that in turn might lead to changes in brain systems that regulate mood, the lead researcher said. If you read Daily Sunlight Can Keep Cancer Away earlier this month, you know about the sun’s ability to prevent cancer. But what you may not know is that its influence on your mental health is just as profound.
When the rats in this study were deprived of light, cells in their brains that control emotions like pleasure as well as cognition began to die. In humans, these are also the brain regions that tend to be underactive if you are depressed, suggesting that without any exposure to light, it may be nearly impossible to feel happy.
Why You Need to Get Sunlight, Even as Fall and Winter Are Approaching
You are probably already familiar with seasonal affective disorder (SAD), which is depression that occurs during the fall and winter months when sunlight is scarce. An estimated 10 million to 12 million people in the United States alone suffer from SAD, while about 25 million Americans suffer from the "winter blues," a condition not as serious as SAD but still requiring attention.
Both SAD and the winter blues are directly related to a lack of sunlight.
Serotonin (a chemical that helps regulate your mood) levels are low in people with depression and, at least one study has found, also in healthy people during the winter.
Since serotonin levels rise in your brain on days with a lot of sunlight, bright light may boost your mood by activating neurons in your brain that contain serotonin, leading to increased levels of the chemical in your brain, researchers say.
Serotonin neuron activity also tends to be higher on brighter days than darker days, even within the same season. This suggests that levels of serotonin in your brain are directly related to how much sunlight is available on any particular day.
In this most recent study, the researchers also pointed out similar findings.
“There is a high frequency of seasonal affective disorder in high latitudes where light exposure is limited, and bright light therapy is a successful antidepressant treatment,” the researchers said.
The take-home message here?
Getting minimal sunlight for prolonged periods of time can negatively impact your mood.
In most of the United States this tends to occur for a good portion of the fall, spring and winter, so a great number of people could be at risk of sunlight-related mood changes and even depression.
Your Body is Designed to be in the Sun
This is why most of us naturally feel like waking when the sun comes up, and sleeping when it’s dark. These inclinations are regulated by your body’s natural 24-hour cycle, or circadian rhythm, which has evolved over many years to align your physiology with your environment.
Your internal clock does much more than just help you sleep in the evening. Your body actually has many internal clocks -- in your brain, lungs, liver, heart and even your skeletal muscles -- and they all work to keep your body running smoothly by controlling temperature and the release of hormones, some of which impact your mood.
Your circadian rhythm, meanwhile, depends on receiving sunlight at the appropriate times (during the day) in order to function properly. If you do not get much sunlight when your body is expecting it -- for example because you’re inside working all day or the weather is cold and cloudy -- it can easily lead to changes in your brain that will negatively impact your mood.
For instance, melatonin, the "hibernation hormone," increases with decreased light, which explains that tired feeling that comes on when it begins to get dark outside -- even if it is only 4:00 in the afternoon.
How to Make Sure You Get the Light That Your Body Craves
In the summer, this is a no-brainer. Spend some time out in the sun. I’ve detailed just how long you should spend in the sun in my upcoming book Dark Deception, and also in this past article.
If you live in many areas of the United States, keep in mind that come late September till late March the sun is lower in the sky for most of the day, which means that a light-skinned person may need longer than 20 minutes in the sun each day, and a dark-skinned person could need one hour to 90 minutes to get all of the benefits of sunlight.
Remember, serotonin, the brain hormone associated with mood elevation, rises with exposure to bright light, and falls with decreased sun exposure. So during the winter months or on days when you can’t get outdoors, it’s really important to make up for this loss of bright light.
You can move to a more ideal climate for the winter but that is impractical for most. Fortunately, there’s a relatively easy way to make up for a lack of sunlight during the winter, and that’s by replacing the light bulbs in your home and office with full-spectrum versions that simulate the qualities of natural outdoor sunlight.
In order to achieve natural balanced sunlight indoors, your light bulbs must contain a full spectrum of color (imagine all the colors of the rainbow). Additionally, true full-spectrum lighting must contain infrared (IR) and ultraviolet (UV) wavelengths.
I have personally used full-spectrum lighting for years now, and can honestly say that they have provided an enormous boost in my ability to tolerate the often gloomy days where I live (near Chicago).
In fact, I have my entire home lit with these full-spectrum light bulbs.
I don’t consider them a replacement for real sunlight (nothing can do that), but they are the next best thing when the sun is not out, or when it’s too cold to spend time outdoors.
What Else Can You do to Boost Your Mood?
Sunlight is at the top of the list, but beyond that you can do the following to help improve your mood at any time during the year:
- Optimize your diet using newly revised Take Control of Your Health nutrition guidelines, in combination with nutritional typing, to determine the foods you need to be eating, in the amounts you need to be eating them.
- Pay particular attention to avoiding grains and sugar because of their specific effects on mood.
- Have your vitamin D levels tested and get them to their optimal levels.
- Get adequate exercise.
- Taking a high-quality source of animal-based omega-3 fats such as krill oil.