The use of light for its antidepressant action dates back to the beginnings of civilization (1)
- in the 1980s, BLT (bright light therapy) was developed in SAD (seasonal affective disorder) to extend daytime photoperiod and counteract winter darkness
BLT is classically delivered through a light box that is equipped with fluorescent tubes and a reflector or diffusing screen:
- patients sit in front of the light box mounted on a table with their eyes open
- BLT may be also administered thanks to light glasses or visors
SAD corresponds to the seasonal pattern of recurrent major depressive episodes occurring during the same time of the year, usually in autumn or winter with spontaneous remission in the spring or summer
- BLT is now considered to be the first-line treatment for SAD in therapeutic guidelines (1)
- the antidepressant effect may be due to light's effect on the biological clock
- by phase advance and alignment of circadian rhythms- and/or actions on non-circadian pathways
- light modulates the activation of efferent serotonergic neurons, decreases the serotonin reuptake transporter (5-HTT) levels, and increases serotonin (5-HT) levels in mood regulatory areas such as the anterior cingulate and prefrontal Cortex
There is evidence that BLT is an effective depression treatment not only to be used in SAD but also in non-seasonal depression and in BD (bipolar disorder) (1).
Results of a systematic review and meta-analysis revealed that BLT was an effective adjunctive treatment for nonseasonal depressive disorders (2):
- additionally, results suggest that BLT may improve the response time to the initial treatment
Reference:
- Maruani J, Geoffroy PA. Bright Light as a Personalized Precision Treatment of Mood Disorders. Front Psychiatry. 2019 Mar 1;10:85.
- Menegaz de Almeida A, Aquino de Moraes FC, Cavalcanti Souza ME, et al. Bright Light Therapy for Nonseasonal Depressive Disorders: A Systematic Review and Meta-Analysis. JAMA Psychiatry. Published online October 02, 2024.