Why some of us get Seasonal Affective Disorder (SAD)

Researchers at Johns Hopkins and the UK may have discovered why some of us get Seasonal Affective Disorder (SAD) in the winter and others don't. This new discovery may also help with insomnia, depression and other circadian rhythm disorders.

For almost a hundred years, scientists believed that the rod and cone cells of the eye were responsible for sight and how our body reacts to light. Recently however, a new protein photoreceptor, called melanopsin, was discovered, and it may hold the key to why some of us suffer from SAD and other body clock problems while others don't.

Melanopsin is a light sensitive protein that lies in the retina of the eye. Under normal light conditions, melanopsin doesn't respond, but in bright light, like sunshine, melanopsin cells become very active. The melanopsin cells are 'responsible for telling our bodies that it is daytime - daylight is always bright light,' according to Dr Rob Lucas at the Imperial College in London . Melanopsin cells help regulate a healthy body clock, and among other things, help keep us active and alert in bright sunshine.

Why we get SAD

Apparently those of us who have body clock problems like SAD may have fewer melanopsin cells in our eyes. Those with few melanopsin cells don't react to brighter light and so their body clocks can't tell the difference between bright, daytime light and darkness. This may be the reason that very bright light and longer duration of bright light is necessary for SAD sufferers to feel normal. Because they have fewer melanopsin cells, it takes more light for their body clocks to work properly.

We were wrong!

For decades SAD researchers assumed that the rod and cone cells were responsible for mediating light, and so they created light boxes designed to stimulate rod and cone photoreceptors. But melanopsin doesn't respond to the same light that rod and cone cells do, and that discovery has dramatically changed the way we deliver light therapy.

Blue not white

While rod and cone cells respond best to white, full spectrum light, melanopsin cells do not. As a matter of fact, they only respond to a specific bandwidth of blue light, in the range of 446-477nm (nanometers). This discovery is critical for SAD sufferers, because it means that they will respond much stronger and quicker to this effective bandwidth of light than to full spectrum. Indeed, studies at Thomas Jefferson and Harvard suggest that this new wavelength of light is not only safer, but more effective as well.

"Our results imply that shorter wavelengths may be more effective and energy-efficient compared to higher energy polychromatic white light for phase-shifting the human circadian pacemaker...Exposure to the optimum balance of light wavelengths may also reduce the undesirable side-effects associated with therapeutic use of light exposure such as glare, visual discomfort, headaches and nausea."

Steven W. Lockely, MD
June 2003, J. of Endocrinology & Metabolism

Apollo has worked with researchers at TJU to develop this new light technology, called BLUEWAVE ® . Because this technology is patented, only BLUEWAVE ® products produce 100% of the effective bandwidth of light without the unnecessary full spectrum light.

The problem with 10,000 lux, full spectrum light

This new discovery may also give us some insight into why some people experience side effects with 10,000 lux, full spectrum light. In traditional light therapy, bright light at 10,000 lux intensity is used. This is because full spectrum is inefficient at producing enough blue light on its own. But by increasing full spectrum enough to stimulate the melanopsin photoreceptors, we may also be over stimulating the rod and cone cells and eye muscles, which result in headaches, eyestrain, excessive glare, nausea, etc. Although BLUEWAVE ® is bright, it is only 1/25 th as bright as full spectrum light, and is much easier on the eyes.

Where is BLUEWAVE Available?

BLUEWAVE® is only available through Apollo's hand held goLITE ™ . The goLITE ™ produces the optimal intensity of BLUEWAVE® light at 20-30 inches. The goLITE's compact design also allows it to be used anywhere.