ABSTRACT
Seasonal Affective Disorder version (SIGH-SAD) or Hamilton Depression Rating Scale with Atypical Depression Supplement (SIGH-ADS). There is, however, a strong placebo effect associated with light therapy. As reported in a study by Eastman et al. (1998), it may take up to 3 weeks to distinguish the light treatment effect against a placebo effect when treating SAD. This is why in the present review we wish to focus on the biological evidence for BLT efficacy, which is less likely influenced by a placebo effect. In SAD, BLT is recognized to impact several biological parameters such as neurotransmitters and hormonal levels, retinal physiology, and circadian entrainment, to name a few. BLT may also be beneficial for patients affected with other psychiatric pathologies less commonly associated with this therapy such as eating disorders, antepartum and postpartum depression, Parkinson’s disease, and sleep disturbances. In addition, we will briefly describe how light and more particularly natural sunlight may change the neurochemical state of healthy individuals.
