Cyclothymia and seasonal variation

Hi everyone, just wondering if anyone knows what current theories are about why moods would vary in people with cyclothymia from season to season. My partner is definitely more depressed between October and March, and less so between April and September. So much so that he's always broken up major relationships in January or February...And I just found some other posts on the forum mentioning the same thing.

I think this is interesting because it's similar to the effects of SAD. But what is actually causing the seasonal oscillation overlaying the shorter, cyclothymic ones? Do light levels change the way the neurones function or something? Is this always a characteristic feature of cyclothymia, or only in some people (like SAD itself)?

...Or in other words, should I buy my partner a lightbox for Valentine's Day?

The reasons for SAD and the seasonal component to other mood disorders are still being studied. However, it may have to do with something a researcher discovered in 2005.

There are cells in the eye that respond to blue light. These cells aren't the same ones that transmit images to the brain. Rather, blue light triggers them to do something that leads to melatonin production. Melatonin is a neurotransmitter. You can take melatonin pills to help you fall asleep. It seems to play a role in mood regulation.

Sunlight on a bright sunny day, especially on summer days when the sun is highest in the sky, carries a lot more blue light energy than household light bulbs. You're exposed a lot less to blue heavy sunlight in the winter. If you use incandescent bulbs, you're exposed to a lot of light that's weak on the blue end. Take a picture indoors with incandescent bulbs using outdoor film or an outdoor white balance setting and no flash. The picture will look ruddy for the reasons I just explained.

Like I said at the start of this, the issue is still being studied. The effect of light on mood disorders varies from person to person, as does the effect of the various medicines one can take. But it seems the quality of the light one's exposed to has a physiological effect that can be manifested in mood disorders.

Fluorescent bulbs are harder to explain because there are actually about six distinct colors that make up the light rather than a continuous spectrum. Some people have a different effect because of fluorescent lights. That kind of light gives them high blood pressure and headaches. They have quite a problem with modern computer screens and cell phones. It's possible their blue sensitive eyeball cells are doing something they shouldn't do instead of or in addition to stimulating melatonin production. Some of them find relief by wearing glasses that block ultraviolet or by putting ultraviolet blocking materials on their computer monitors. That doesn't get rid of the visible blue. But the results suggest those blue sensitive cells also respond to the presence of invisible wavelengths beyond the blue end of the spectrum.

You won't know if a special lighting arrangement will do anything for your partner until you try it. I have a coworker with major depression. She's fortunate to have a desk by a window. She opens the shade during winter. She says it helps.