Tag Archives: circadian rhythm

Bright Light: Depression, Insomnia, and the sleep/wake cycle


I recently wrote an article for the Natural Medicine Journal about a study that showed the positive effects of wearing bright light glasses to treat depression. Bright light therapy has been popular for the past few decades to treat seasonal as well as non seasonal depression, but this is the first study to utilize a device that is worn like a pair of glasses and shines light down into the eyes of the wearer. In the past, subjects have used light boxes which work equally well, but the glasses have the advantage of allowing the wearer to be able to do other things during treatment.

While this study is interesting in itself, it brings up some fascinating questions about the role of light and dark, the sleep/wake cycle, and the establishment of a healthy circadian rhythm in mood regulation.

In this particular study, the participants (who were all teenagers receiving inpatient treatment for depression) were asked to complete a “Chronicity” questionnaire to establish their most productive time of day. None of the participants were found to be strongly morning people. There are many studies that have found a link between “eveningness” and depression. Additionally, insomnia (which is associated with eveningness) has been found to have an even greater impact on negative emotions.

So how does bright light impact the body to influence emotion and the circadian rhythm? In studies of bright light therapy, the light used emits 10,000 lumens, which is roughly equivalent to sunlight 40 minutes after sunrise on a clear day. When light hits the retina of the eye, the retina itself actually produces serotonin and dopamine, which help to maintain a good mood. The glasses in particular (as well as sunlight) emit blue light, which is the part of the visible light spectrum that is most stimulatory. We can surmise that if a person is spending the majority of their most wakeful hours when it is dark, it is possible that they aren’t making as much of these chemicals.

Conversely, blue light in particular suppresses retinal production of melatonin, which is one of the primary neurotransmitters responsible for sound sleep. Most of us have heard that watching screens such as the computer, TV, or phone before bed can impact sleep. This is because blue light emitted from these screens prevents the body from making melatonin which is necessary for sleep. Studies have found that people who wear blue-light blocking glasses for three hours before bed can correct insomnia and have more restful sleep.

Regardless of your light source, starting the day with exposure to healthy bright light will help you to make the chemicals you need to keep your mind feeling happy and at ease. At the end of the day, minimizing exposure to bright light and blue light in particular will help your body fall asleep more easily and have a more restful night!