How many Ways does it Take to Shed Light on the Lows_

by Marwan Hamed, MPH

Studies from around the world have shown that light therapy works as well as pills for treating seasonal and non-seasonal depression — the lows. But are you curious about how light counteracts the lows? Read on!

Light shifts your biological clock

One of the strongest explanations for how light might counteract the lows is by shifting the timing of your biological clock. This makes sense, because light is the most powerful time-setter, especially during the first hours of the day and the last hours of the night. This information is helpful when treating conditions like SAD, where early daylight is most potent for treating the winter blues. When repeated over time, early daylight exposure leads to a needed speed up of the inner clock, which may have slowed down in winter due to later sunrises. This can help people struggling with the winter blues to wake up earlier and feel more refreshed!

Did you know?

Light is the most powerful zeitgeber!

A zeitgeber is a natural cue for the internal biological clocks of the body.

Originally coined by German scientists, English readers can understand zeitgeber as time-setter.

But this explanation doesn’t apply to everyone since some people need bright light therapy in the evening to adjust their fast biological clocks later, while some people with bipolar disorder do best with midday bright light therapy, when the clock is less sensitive to light.

So, even though light shifts your biological clock, it’s not the only explanation of why light is excellent at counteracting the lows.

Light signals also bypass the clock, right into your brain

A recent study from the US National Institutes of Health hints that light can counteract the lows without shifting the biological clock. They found that light signals go straight to brain centers that directly affect mood state. Until now, these routes into the nervous system have been studied only in animal experiments, and since the animals were active mostly at night, and slept during the day, the findings still need to be extended to people with mood disturbances, which will take years of new clinical research.

But still, the finding that non-clock brain centers can influence mood state gives us something to think about as we continue to find ways to learn more about how we function physically, mentally, and emotionally.

Both light to the clock and to the newly identified mood centers signal the brain through light to the eyes. The light-sensitive cells in the eyes are different from other cells that pick up visual responses. In fact, a person could be visually blind, but their eyes would still send light signals to their brain, affecting the speed of their biological clock and their mood state.

Light to your blood

Did you know that our eyes have a rich blood supply? This knowledge suggests another route for light signaling the brain in ways that could affect our mood and behavior.

Recent research by CET’s Dan Oren, MD, has provided the first evidence of light’s direct action on circulating blood in the eyes.  If carried out in additional lab research, it would add to the theory that light can counteract the lows by acting on blood passing through the eyes.

Dan’s theory is based on known similarities between chlorophyll — plant molecules used to absorb light for energy — and hemoglobin molecules in human blood that bind and release gases needed for our survival. There are already test-tube studies using human blood, and animal studies of blood-rich eyes of pigs — which are like human eyes — that support this theory, but still more research is needed before we can confidently conclude that the light/blood effect acts in the brain to counteract the lows.

Light shines on eyes


Blood gases released


Blood sends signals to the brain, counteracting the Lows




Should you use light therapy?

Though scientists still have a lot to learn before we can understand exactly how light works to counteract the lows, one thing for sure — it works!

The effect may involve independent or combined actions on our biological clocks, other brain centers, blood, or other ways yet to be discovered. But one thing for sure is that it can work very well for people who follow CET’s guidance on light therapy, which is based on years of clinical trials for seasonal and nonseasonal depression. And we have selected the best research-based light box to recommend to CET visitors. Before starting light therapy, it is wisest to have a personal consultation with a clinician who already knows when and how to use this drug-free approach or is willing to sit down with you to jointly learn the ropes. Prepare for the session by completing our online confidential self-assessments and printing out the results for discussion.

So, if you think that you are struggling with your mood, then there’s likely a light treatment that can help to brighten you up! If you’re exploring this option for the first time, you’ll have highest success by engaging your doctor or therapist, until you have worked out the details and can proceed on your own.  Need help figuring out how to get to the right people? A call to your nearest university medical center mental health program can often produce the lead you need. Although CET has limited referral information outside major metropolitan areas, contact us if you need further advice.

At CET, we love finding ways to help people, but we rely on your feedback and help in return. So please participate and help us to help more people!

Marwan Hamed is a freelance writer for CET.