Many of us commute to and from work in cars or busses, on a subway or by train; we work indoors under fluorescent lighting and then when we finally make it home we spend more time indoors doing household chores, helping kids with homework, using the computer, or watching television. Even when we exercise, our workout is just as apt to be inside as it would be outdoors. No wonder we’re light-deprived!

When we don’t have enough light we may start feeling down and find it difficult to concentrate. Our energy levels can drop, we become less active, oversleep, irritable and even depressed; we may gain weight and even withdraw socially. These are symptoms of Seasonal Affective Disorder (S.A.D.), which is one effect of not getting enough sunlight. S.A.D. can set in as early as November and last through March, or longer depending on lifestyle.

According to scientists, the lack of light we experience in the winter means that the neurotransmitters in our brain fail to suppress melatonin, the hormone that makes us feel sleepy, and fail to trigger enough serotonin – a chemical in our brain that controls our mood.

Melatonin helps trigger the sleep cycle and it slows down our body’s functions down while we sleep. If your body is short of melatonin, you won’t get the deep sleep you need at night. We need light in the daytime to slow down the production of melatonin so that our body clock gets reset and we have proper levels of it at night.

Most people feel more alert, have more energy and are in a more positive frame of mind when they are getting enough sunlight. Time spent in the sun elevates serotonin level and makes us feel happier.

Research has shown that light therapy – simulated sunlight – can offer benefits for S.A.D. as well as sleep disorders, pre-menstrual syndrome (PMS) and non-seasonal depression. What light therapy aims to do is to regulate your melatonin cycle to proper levels — low in the daytime and high at night. It involves regular exposure of a set duration, optimal wavelength and distance from a bright light source.

The degree to which light penetrates our skin depends on the colour (spectral range) and intensity of light. The light around us is comprised of many different colours that have different wavelengths and vibrate at different frequencies. White light is a mixture of all colours, and white light has the same wavelength as sunlight.

LUX is the measurement of intensity of a light source. Sunlight outdoors on a sunny day can be up to 100,000 lux, which is 1,000 times what one might find in many homes or offices. An intensity of more than 2,500 lux for an appropriate duration may provide the benefits of improved mood, increased energy and better sleep.

So next time you’re feeling “sad” consider what type of light you’re exposed to in a day (e.g. full spectrum vs. fluorescent) and for how long. Understand that we all need sufficient beneficial light to synchronize our body clock and transmit energy throughout our body.

If you are considering light therapy be sure to discuss its suitability and possible side-effects with your physician.