2What is white light therapy?
White light therapy refers to the daily exposure to bright, full, or limited spectrum artificial light. And the term White light therapy is distinguished from phototherapy. Phototherapy is used in dermatology and in the NICU (Neonatal Intensive Care Unit) for newborns to reduce hyperbilirubinemia. The initial use of white light therapy was in the field of psychiatry in 1981 and arose from circadian rhythm hypotheses for seasonal and nonseasonal depression.
The treatment of Seasonal affective disorder “SAD” is similar to that of other forms of affective disorder, except that white light therapy is recommended as the first-line option for winter SAD. White light therapy conventionally means the administration of visible light producing at least 2500 lx at eye level. Important parameters for light therapy generally include the intensity, duration, and timing of daily light exposure. The intensity of light is usually expressed in lux (lx), a unit of illuminance corrected for the visual spectral responsiveness of the eye.
Many controlled studies of light therapy have been conducted by researchers around the world. Although there are limitations of design to these studies, several qualitative overviews have concluded that white light therapy is an effective treatment for winter SAD. In addition, two meta-analyses also confirm the efficacy of white light therapy against placebo controls.
Whilst the relatively steady head position reduces the usual variability in levels of direct light input relative to that experienced outdoors, fluorescent white light therapy is considered relatively safe for the eyes. A follow-up study did not show any ocular damage after several years of treatment, with a cumulative duration of exposure for up to 1250 hours. There are no documented reports of induced ocular damage resulting from standard light therapy procedures.