Can you sleep at night?
New research may change how we use light to treat sleep disturbance and seasonal depression.
Long ago, people lived according to the cycle of the sun. Ancient people woke up as the sun rose, and went to sleep as the sun set. Humans developed something called a circadian clock in their bodies, which is affected by light, and influences sleeping patterns, body temperature, brain function and hormone levels.
Many people today seem to stay up late, and because of this they have a hard time getting up in the morning. Being exposed to room lights, computer screens, or the light of other electric equipment late at night disturbs your circadian clock. Therefore you may find it hard to get up.
But in a study published 12 May 2010 in Science Translational Medicine, Joshua Gooley and his team announced some surprising results which will affect how we use light to treat sleep disturbance and seasonal depression.
The eyes of humans and other mammals have special cells called ‘melanopsin-containing retinal ganglion’ which are thought to help regulate circadian rhythm. As their name suggests, they contain a certain pigment called melanopsin, which absorbs blue light. So until now many researchers believed that only blue light is involved in regulating the circadian clock, and many devices which use blue light for the treatment of sleep disorders have been developed. However Joshua Gooley and his team showed that the other wavelengths of light can affect the circadian clock.
Our eyes also contain cells called cone photoreceptors which allow us to see color. In this study the researchers discovered that these cells may also be involved with the control of the circadian clock. Researchers exposed people to blue light and green light, and discovered that while blue light has a strong affect on the circadian clock, green light also has an affect under short term, low light conditions. This suggests that not only melanopsin-containing cells, but also cone photoreceptors have a function relating to circadian rhythms.
These results indicate that light therapy for sleep disorders might be optimized by using blue as well as other visible lights.