Psychologists have developed a test to determine if one is at risk for Seasonal Affective Disorder (SAD). It's a bit complicated, and you certainly can't do it for yourself.
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SAD depression brought on by less light during the winter months. Do you suffer from this?
I dont but I have a few coworkers who do. One of them brings in this light to work, that they place on their desks, and turn on for 20 minutes at a time. It is supposed to give the brain the feeling that there is more light around than actually present. Not sure how well that works though, they still seem pretty depressed.
There is a Sister at my old Branch that suffers from this. She has replaced all of her incandescant bulbs in her house with true light bulbs. I use them too ~ I have found that GE Reveal bulbs to be the best for the price.
I have gone to these bulbs too and have even changed out all of the fluorescent bulbs too with the Bath and Kitchen true light ones. They do make a remarkable difference.
Incandescent bulbs give off a yellow light, and in the winter time it can be depressing. I switched because I wanted a truer light to see colors by, and I really liked them.