By Dr. Mercola
When you climb into bed for the night, is your bedroom “littered” with dim light from streetlights, passing traffic, a computer, night-light or television set?
Even if the light is so dim that you can easily sleep through it, light pollution can prompt biological changes that have a very significant, and potentially serious, impact on your physical and mental health.
Obvious examples would be the glow that can be seen from miles outside of a big city, or the absence of stars in the night sky if you live in an urban environment.
More subtle examples of light pollution are the strips of light that come in around your curtains at night, or even the glow from your clock radio.
All of these light sources disrupt the natural rhythms of nature, as like most other creatures, humans need darkness. When this natural rule is violated, the consequences can be steep …
Dim Light at Night May Lead to Depression
A study done with hamsters at Ohio State University Medical Center has found that chronic exposure to dim light at night can cause signs of depression after just a few weeks.1 The study also showed changes in the hamsters’ hippocampus similar to brain changes seen in depressed people. They pointed out that rates of depression have risen along with exposure to artificial light at night:
“Exposure to artificial light at night (LAN) has surged in prevalence during the past 50 years, coinciding with rising rates of depression.”
The link could be due to the production of the hormone melatonin, which is interrupted when you’re exposed to light at night. There are many studies that suggest melatonin levels (and by proxy light exposures) control mood-related symptoms, such as those associated with depression -- especially winter depression (aka, seasonal affective disorder, or SAD).
In a study published by researchers at the Oregon Health and Science University (OHSU), it was found that melatonin relieved SAD.2 The study found insomniacs have a circadian misalignment in which they are “out of phase” with natural sleeping times.
This misalignment can be corrected either by exposure to bright lights (during daylight hours), or by taking a melatonin supplement at a certain time of day. While your body will begin to produce melatonin only after it’s dark outside, the level of melatonin produced is related to the amount of exposure you have had to bright sunshine the previous day; the less bright light exposure the lower your melatonin levels.
Yet another study about melatonin and circadian phase misalignment found a correlation between circadian misalignment and severity of depression symptoms.3
Studies have also linked low melatonin levels to depression in a variety of populations, including multiple sclerosis patients4 and post-menopausal women.5 Clearly, anything that negatively effects melatonin production is likely to have a detrimental effect on your mood. Melatonin’s immediate precursor is the neurotransmitter serotonin, which is a major player in uplifting your mood.
Too Much Light at Night May Also Contribute to Cancer
Normally, your brain starts secreting melatonin around 9 or 10 pm, which makes you sleepy. These regularly occurring secretions thus help regulate your sleep cycle.
The good news is the condition appears to be reversible by simply going back to regular light-dark cycles and minimizing exposure to artificial light at night. But when light receptors in your eyes are triggered, such as by the glow from your television set, they signal your brain to 'stay awake.' To do that, your brain stops secreting melatonin, which is not only a hormone but also a potent antioxidant against cancer.
Melatonin is secreted primarily in your brain and at night it triggers a host of biochemical activities, including a nocturnal reduction in your body's estrogen levels. It’s thought that chronically decreasing your melatonin production at night -- as occurs when you’re exposed to nighttime light – thereby allows your body to be exposed to higher estrogen levels, which increases your risk of developing estrogen-sensitive cancers, such as breast cancer.6 >
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