Light and Cognition

12th May 2015

The relationship between light and cognition starts at a biological level with the circadian rhythms. It follows an approximate 24 hours cycle of physical, cognitive, and behavioural changes responding and adapting primarily to light and darkness. When this system is disrupted it can have dire consequences from anxiety disorders, depression to chronic disease.

We are learning that spending more time in artificial light due to work environments is changing our circadian rhythms. Firstly, we are away from natural light, which not only informs our body of biological timings, but we also prevent ourselves from getting vitamin D, which plays a role in brain function. The less we are exposed to natural light the less we are able to synchronize our biological rhythms with the day/night cycle. Therefore we are out of sync. This may not seem important, but if we are not giving the body its timings, it will be performing functions when it is not supposed to, which has dire consequences to our health. Natural light also, reduces the effects of cortisol, which is impedes cognitive functions like cognitive flexibility, theory of mind, and memory. We cannot prevent stress, but if we had more natural light in workspaces, people would be able to return to homeostasis faster and perform better. For example a change in cognitive flexibility affects how quickly you can adapt to change or new stimuli, which essential for complex problem solving.

Secondly, staying in artificial light at night including the light emitting from electrical devices keeps us in a state of “on” which can lead to depression, anxiety disorders and chronic disease. Studies looking at electrical light emitting from our devices, which most of us use right up to the moment we fall asleep, show that screens like mobile phones and computers emit optical radiation at short wavelengths, close to the “peak sensitivity of melatonin suppression”. What this means is the body will suppress the release of melatonin, because it thinks it still needs to be awake. Melatonin is a hormone released in animals and other biological forms including bacteria in anticipation of the daily onset of darkness. It influences the matching of rhythmic behavioural or physiological events with their appropriate period according to environmental oscillation. In other words melatonin regulates when certain functions are to happen in relation to the onset of darkness such as the regulation of blood pressure and sleep.

The big take away is that nothing is better than natural light or matching the natural light cycle. So as the day progresses move to dimmer light and turn all lights in your sleeping environments, so you can fully switch off and rest.