The Psychological Effects of Lighting

Why is this relevant? It is important to understand that when we are placed into light, we are exposed to a broader range of wavelengths than what we can see with our eyes. Light sources produce bands of wavelength that far exceed the visible light spectrum. Humans can detect IR wavelengths by feeling the heat they generate. UV wavelengths do not produce heat and cannot be “sensed” by the body, but they can damage skin.

The sun produces frequencies throughout the electromagnetic spectrum. By the time the sun’s energy reaches the Earth’s atmosphere, however, the remaining wavelengths are in the range from IR to UV. The atmosphere effectively blocks most of the UV and IR radiation from reaching the earth’s surface, protecting us from most of the sun’s harmful rays. The sunlight that reaches us is a white light, composed of an equal distribution of wavelengths across the visible light spectrum. It is a full-spectrum light, meaning it has a broad, flat, spectral power distribution (SPD).

How We Sense Light

Aside from providing us with an ability to see, the retina contains receptors that respond to light, independent of the visual system’s rods and cones. These receptors send information about the presence or absence of light directly to a different section of the brain called the suprachiasmatic nucleus (SCN), located within the hypothalamus. By sensing light and dark, our bodies can become synchronized to the movement of the Earth’s rotation and its orbit around the sun. Although the SCN receives input from other stimuli, the most potent stimulus for our synchronization to the twenty-four-hour day/night cycle is through the temporal exposure to light. Wavelengths between 460 and 484 nm (blue light) have been shown to be the most effective at stimulating these retinal cells. Light therefore enables us to see and also provides us with a mechanism with which we can generate a biological clock, known as a circadian rhythm, which syncs our bodies to the Earth’s rotation and orbit.

By closing our eyes, it is possible to “turn off” one’s visual system. However, dropping the eyelids is not an effective way to stop light from entering the eye. Eyelids are merely a protective mechanism that keep our eyes moist, help wipe away debris, and allow us a way to turn off visual sensory input. However, depending on the intensity of ambient light, closing one’s eyes may be akin to putting non-blackout curtains on an outdoor window during a sunny day. Napping in a room with ambient light will more than likely stimulate the SCN, telling the body that it is daytime.

All About Melatonin

Why does this matter? A small gland in the brain, called the pineal gland, is also connected to the SCN. If the pineal gland receives information through the SCN pathway that indicates it is nighttime, it will produce and release the hormone N-acetyl-5-methoxytryptamine, also called melatonin, into the bloodstream. Interestingly, the pineal gland has been referred to as the third eye in many cultures for thousands of years. By responding to light via the SCN pathway, it does, in a sense, act like an eye, although it sends the brain no spatial information and can’t stimulate any associative memories.

The pineal gland commonly becomes partially calcified as we age, as often seen on CT exams. Although many think this calcification does not appear to have any effect on the pineal gland’s function, one study found an association between pineal calcification and a loss of directional sense. The pineal gland’s release of melatonin has significant effects on the brain and on maintaining the body’s overall health. Melatonin is synthesized during sleep in the darkness of night, with peak production usually around 2 am, both during the summer and winter. Circadian rhythm is therefore timed to a cyclical production of melatonin during darkness and non-production during periods of light. Melatonin provides the cells in our body with a chemical biological clock that indicates to the body’s systems the length of the night and signals the brain as to when it is dusk and dawn. Longer nights during winter result in greater melatonin secretion, and shorter nights during summer result in less melatonin production. In this way, our bodies can differentiate between the seasons.

Physiological Effects of Melatonin

Melatonin has important physiological effects. Higher levels (longer nights, deeper sleep) strengthen the immune system, while lower levels (shorter nights and/or interrupted sleep) suppress a number of immune system actions. Melatonin is a powerful antioxidant and functions as an anti-cancer agent by interacting directly with cancer cells. Melatonin also affects the production and release of proteins such as reproductive hormones, which may directly or indirectly affect cancer growth. Melatonin has also been shown to be an epigenetic regulator, meaning that the presence or absence of melatonin in a cell can determine which genes in the DNA are switched on and off. Abnormal melatonin levels are commonly encountered in a number of psychiatric and neurological disorders, including depression.

Disruption of Melatonin Production

Melatonin is an important hormone that ties us to our environment, strengthens our immune systems, and even affects our genetic expression. So, what happens when melatonin production goes haywire? First, consider why melatonin production might be insufficient. As mentioned earlier, melatonin production ceases when the pineal gland senses light. Exposure to a room light in the evening, before bedtime, has also been shown to have a profound suppressing effect on melatonin production. Even viewing a lit LED screen before going to sleep has been shown to significantly lower melatonin levels and suppress sleep. The effect is more profound in children and teenagers than in adults. In fact, the degree of melatonin suppression caused by nighttime light exposure in children is almost twice that for adults. Blue light suppresses melatonin to a greater extent than longer wavelengths (redder colors). Insomnia can be attributed in some cases to decreased melatonin production, particularly in the elderly. Perhaps this may sometimes be related to elderly people falling asleep with the television on, or perhaps not being able to fully close their eyes while they are sleeping.

Studies have indicated that exposure to low levels of artificial light in the home or office during the day and/or increased light at night may disturb melatonin production and therefore disrupt circadian rhythms. We are designed to be exposed to sunlight during the day and darkness at night — otherwise, we can become out of sync and lose our circadian rhythms.

Disrupted circadian rhythms caused by light exposure at night have been associated with sleep, gastrointestinal, mood, and cardiovascular disorders, possibly through diminished melatonin production. There is epidemiological evidence that disrupted circadian rhythms and insufficient melatonin production have caused an increased incidence of breast cancer in:

• Night shift workers. Women who do long term shift work have a 40 percent increased risk of developing breast cancer!
• Flight attendants potentially suffering from jet lag and night shift work.
• Increased ambient light at night in the bedroom.
• Increased light in the community at night (light pollution).

Additional studies show that cancer risk in general increases with deficient melatonin, meaning that if one’s circadian rhythms are disrupted, one is at risk for developing many other different types of cancer.

So what should you do if you are stuck with a job where you are required to do overnight work? Quit? Limiting the number of people required to work graveyard shifts throughout the workforce would indeed lead to benefits in society’s overall health.

How to Use Lighting to Your Advantage

For those who are not required to work graveyard shifts, there are several lifestyle changes that can help maintain normal melatonin production and balanced circadian rhythms.

First of all, pick a bedtime, ideally before 1 am, and try to stick with it. When your body senses it is time to go to sleep, it will naturally produce hormones that prepare your body for sleep. If you fight this urge, you may find that your sleepiness will dissipate and you will then have a hard time falling asleep later.

If you like to read before bed, choose your reading light carefully. Consider using a small spot-type LED light that will illuminate your book pages, but not the room. Tablets and computers should not be viewed in bed prior to sleeping, especially by teenagers. The TV should be turned off when you go to sleep. If needed, put a timer on the TV to have it automatically shut off at a specified time, soon after you anticipate falling asleep.

Make sure your bedroom is dark. Many electronic gadgets are equipped with LED indicator lights that faintly glow in the darkness of the bedroom. Put black tape over them or place an object in front of each indicator light so you can’t see them with your eyes open. Studies have shown that even periodic, faint flashes of light in an otherwise dark bedroom can delay and diminish melatonin secretion,22 even if the sleeper does not awaken. If you have an alarm clock with a lighted display, dim the display or turn it off. If you live in an area with light pollution, purchase blackout blinds or curtains. When the window treatment is closed, no exterior light should enter the room.

If these suggestions are not possible, an eye mask can help. These products typically consist of a soft fabric overlying a sponge-like insert with elastic straps. Some masks are filled with lavender or other herbs. It may initially be difficult sleeping with a mask on, but after a few nights, you will more than likely find it easier to fall asleep with them on and your nights will be more restful.

Melatonin Supplements

In most cases, modifications to one’s lifestyle should restore normal melatonin levels. If not, though, a melatonin supplement can be used. Melatonin supplements are produced and marketed as sleep enhancers and treatments for depression and jet lag. Many additional applications for melatonin supplementation exist. Even people taking statins have been shown to benefit from melatonin supplementation as melatonin has a protective effect on the liver. No significant side effects are associated with the use of melatonin.

Excessive melatonin production can occur in people who do not get enough light exposure, as can happen during winter months in the northern latitudes. Too much darkness or insufficient daylight exposure can cause seasonal affective disorder (SAD), a condition resulting from the overproduction of melatonin. Many of us who go to work before the sun rises, stay indoors all day, and then leave work as the sun sets are well aware of how the winter months slowly drag by as we get more and more glum. Regardless of one’s job, it is important to take time every day to bathe in outdoor light. Even on cloudy days, going outside into daylight, even if it is just for ten minutes, will improve your mood and well-being. SAD can be successfully treated without medication by administering daily light “therapy.”

Reprinted with permission from Toxic Home/Conscious Home, by Rob Brown M. D. and published by Healthy Berry LLC.