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Researchers from the University of Maryland's School of Medicine have determined that just one hour of bright light therapy significantly reduces depression and depressed moods.
Depressed patients were given one hour of bright light therapy or an hour of dim light therapy as a placebo. The researchers found that the patients given bright light therapy had reductions in their depression scores ranging from 120% to 130%, using two different depression-testing systems.
The research is significant because it applied a placebo test against the light therapy system - something previous light therapy studies have not done.
In a related study, some of the same researchers tested 15 depressed patients who were diagnosed with seasonal affective disorder. They administered different lengths of 10,000 lux of white cool fluorescent light for 20 minutes, 40 minutes and 60 minutes and compared the depression scores with the depression scores of the patients prior to treatment.
The researchers found that 40 minutes of the light therapy significantly improved moods among the patients, and reduced their depressed states. The improvement was greater than the 20 minutes of therapy. But surprisingly, the 60 minutes of light therapy did not result in significantly better improvement of depression than either the 20 or the 40 minutes of therapy.
Depression levels in the latter study were measured using the 24-item NIMH scale, a standardized measurement of depression symptoms. The level of seasonal affective disorder depression was gauged using the SIGH-SAD scale (Structured Interview Guide for the Hamilton Depression Rating Scale). They also used Wilcoxon Signed Rank testing. Other studies have used the Profile of Mood States-Depression-Dejection subscale and the Beck Depression Inventory II.
The researchers used a 10,000 lux light box made by Sunbox for the bright light therapy. The patients starred at the center of the light box to receive their therapy.
The findings are consistent with other studies, most that utilized both synthetic light, but some that used natural light. In one, McGill University researchers found that natural bright light significantly reduced acute tryptophan depletion-related depressed moods.
Still other studies have shown that bright light increases cognition, improves sleep and has a myriad of other benefits.
Virk G, Reeves G, Rosenthal NE, Sher L, Postolache TT. Short exposure to light treatment improves depression scores in patients with seasonal affective disorder: A brief report. Int J Disabil Hum Dev. 2009 Jul;8(3):283-286.
Reeves GM, Nijjar GV, Langenberg P, Johnson MA, Khabazghazvini B, Sleemi A, Vaswani D, Lapidus M, Manalai P, Tariq M, Acharya M, Cabassa J, Snitker S, Postolache TT. Improvement in depression scores after 1 hour of light therapy treatment in patients with seasonal affective disorder. J Nerv Ment Dis. 2012 Jan;200(1):51-5.
aan het Rot M, Benkelfat C, Boivin DB, Young SN. Bright light exposure during acute tryptophan depletion prevents a lowering of mood in mildly seasonal women. Eur Neuropsychopharmacol. 2008 Jan;18(1):14-23.