Controlled exposure (by duration, intensity and frequency) to selected light sources has proven to be effective as an elective treatment of SADs (seasonal affective disorders or seasonal autumn/winter depression).

Recently, it has also been proven that “light therapy” is likely to be effective also in other illnesses such as:

• major depression (Non Seasonal Disorder/NSD) and forms of bipolar affective disorders (Yamada, 1995;Lam, 1998)
• premenstrual depression (Lam, 199199)
• post- and ante-partum depression (Epperson, 2004)
• bulimia nervosa (Blonin, 1996;Lam, 1998;Braun, 199199)
• sleep disorders (delayed and advanced sleep phase syndromes)(Abbot, 2003; Reich, 2004)
• Alzeimer’s disease (Alzeimer dementia, Skjerve, 2004).

The efficacy of “light therapy” in major depression was supported by Yamada in 1995 and by Benedetti in 2004, and for bipolar forms by other researchers.

Recent controlled trials appear to prove the efficacy of “light therapy” when combined with the use of Selective serotonin reuptake inhibitors (SSRIs), by reducing time to effect, prolonging effect duration, reducing dose levels and enhancing efficacy (Benedetti, 2004).

According to Kripke (1992), drug latency times drop to just one week when they are used in association with “light therapy” and this theory is currently the object of an in-depth analysis (meta-analysis) (Tunnainen, 2004); Golden, awaiting publication)

Light therapy is particularly useful because it reduces time-to-effect to under a week in seasonal depression (autumn-winter or recurrent depression), when light is provided in the early hours of the morning (dawn light) for no less than half an hour a day for at least five consecutive days, with illumination of at least 5000 Lux, Color Temperature ranging from 4500 to 8000 Kelvin, and a frequency spectrum (electromagnetic wavelength) over 480 A, at the blue-green end of the scale.

The only undesirable effects that could be attributed to Light therapy concerns potential retinal damage (macular degeneration at frequency spectrum values shorter than 480 A (blue-green light).

Optimal exposure times could carry some risk when associated with unusually long treatment cycles.

The recommendation to choose artificial lighting with a spectrum primarily focused in the green band is not beneficial since these lamps do not guarantee the same levels of efficacy and require considerably longer exposure times.

However, it should be noted that there are different types of depression, each stemming from different causes (i.e. genetic, environmental, social, stress, etc.).

Spontaneous Internal Desynchronization may be one cause (or a concomitant cause) of some of these depressions. Light Therapy is particularly effective when used to treat seasonal depression (Seasonal Affective Disorder/SAD).

The use of light with a wavelength longer than 480 nm (because shorter wavelengths could cause retinal damage) is discouraged by some authors, who while admitting that blue light is harmful to the retina, observe that all the evidence points to the fact that the damaging wavelengths are around 450 nm or less. Recent studies show that blue light with a wavelength of 464-480 nm has the greatest impact on the human circadian system.