What is light therapy and how does it help depression?
By Corgan Blosch and Rose George MD
Every human being needs sunlight. Not only does sunlight provide us with Vitamin D, but it also helps us regulate the chemicals (neurotransmitters) in our brain. There is a special area in the brain called the suprachiasmatic nucleus, which controls the regulation of melatonin and temperature. This part of the brain fluctuates cyclically, but it needs external stimulation to maintain a 24-hour cycle. The key stimulant is light and darkness over the course of the day. Our brains produce melatonin, which is helpful for sleep, and serotonin, which is helpful for waking. When the balance of these becomes skewed, it can present depression symptoms such as fatigue, lack of motivation, loss or abnormal increase of appetite, and irritability.
When someone is already suffering from these depression symptoms, the changing of seasons can make those symptoms worse. One way to treat this aspect of depression is called Light Therapy. While Light therapy is most common for Seasonal Affective Disorder, it has shown to have some benefits for those diagnosed with Major Depressive Disorder as well.
Light therapy uses a bright, artificial light to help regulate your circadian rhythm and help produce melatonin and serotonin appropriately. During light therapy, a person will sit in front of this light, usually for around 30 minutes. The person can eat, read, watch TV, or even work on the computer while basking in this light. The lightbox should emit at least 10,000 lux (light intensity) and the person should be about a foot away from the lightbox. Time of day was also evaluated and researchers found that morning light therapy was more effective. Light therapy was more effective for mild to moderate depression with less other mental health issues contributing to mood then for more severe depressive cases.
More scientifically, the light this box produces works through the eyes and activates the circadian pacemaker of the brain (the suprachiasmatic nucleus). This helps regulate the cyclical nature of the brain, alleviating some of those depressive symptoms such as fatigue and low motivation. The precise mechanism of the effect of light therapy is still being researched, and is somewhat elusive. We do know that some studies have shown that light therapy can help decrease the severity of depression in those diagnosed with Major Depressive Disorder, especially around the winter months if they have a seasonal aspect to their depression.
References:
Chang, C.-H., Liu, C.-Y., Chen, S.-J., & Tsai, H.-C. (2018). Efficacy of light therapy on nonseasonal depression among elderly adults: A systematic review and meta-analysis. Neuropsychiatric Disease and Treatment, Volume 14, 3091–3102. https://doi.org/10.2147/ndt.s180321
Perera, S., Eisen, R., Bhatt, M., Bhatnagar, N., de Souza, R., Thabane, L., & Samaan, Z. (2016). Light therapy for non-seasonal depression: Systematic review and meta-analysis. BJPsych Open, 2(2), 116–126. https://doi.org/10.1192/bjpo.bp.115.001610
Sloane, P. D., Figueiro, M., & Cohen, L. (2008). Light as Therapy for Sleep Disorders and Depression in Older Adults. Clinical geriatrics, 16(3), 25–31.