The same type of high-intensity light therapy used to treat seasonal affective disorder (SAD) and as an adjunctive treatment for non-seasonal depression has been found to boost testosterone and improve sexual satisfaction in men with low libido.
In a study by Andrea Fagiolini and colleagues, men with low sexual desire or trouble getting aroused were exposed to the high intensity light (10,000 Lux) for a half hour upon waking. Compared to men who used a lightbox that filtered the light to only 100 Lux, men exposed to the high-intensity light for two weeks showed increased testosterone in the blood and reported greater sexual satisfaction. Testosterone levels increased from around 2.1 ng/ml to 3.6 ng/ml in the high-intensity light group. (There were no significant changes in the comparison group.) Light therapy is quite safe for people without eye problems.
Fagiolini explained that in the Northern hemisphere, testosterone production declines from November to April and then rises again through the spring and summer, peaking in October. He suggests that the light therapy mimics the effect of summer light on the body, perhaps by inhibiting the pineal gland, which secretes hormones.
Fagiolini and colleagues hope to replicate the study with a greater number of participants and to determine how long the results may last.The study of 38 participants was presented at the 29th Congress of the European College of Neuropsychopharmacology in 2016.
A recent study of 93 adults with bipolar disorder suggests that midday bright light therapy can be an effective adjunctive treatment for bipolar depression. The study by Dorothy Sit and colleagues was presented at the 2015 meeting of the Society for Biological Psychiatry. Participants had been diagnosed with bipolar I or II disorder, were in a current episode of depression, and were taking stable doses of mood stabilizing medication. They were randomized to receive either 7000-lux broad spectrum light for 45 to 60 minutes each day for six weeks or 50 lux dim red light. The comparison was dramatic: remission rates were 56.5% among those exposed to the 7000-lux light, and 14.3% among those who were exposed to the dim light. Those who received the bright light also reported better sleep quality and less suicidality.
Editor’s Note: These results are striking and raise the issue of whether midday bright light is more effective than early morning bright light, the usual recommendation for seasonal affective disorder (SAD) and other forms of depression. Until comparative studies are available, using midday light may be the way to go.
A study by Pinar Güzel Özdemir and colleagues in the Journal of Clinical Psychiatry indicates that bright light therapy may improve the effects of antidepressant venlafaxine (Effexor) in patients diagnosed with major depression for the first time. In the study of 50 inpatients, half received 150mg of venlafaxine at 7am each morning, while half received 150mg of venlafaxine plus 60 minutes of 7000 lux bright light therapy at 7am each morning. Beginning after the first week of treatment, both groups showed significant improvement in depression and negative mood states throughout the eight-week study. However, at weeks 2 and 4, the patients who received bright light therapy showed greater reductions in depression, with 76% reaching the target goal of treatment after four weeks compared to 44% of the venlafaxine-only group.
Both venlafaxine and combined treatment with venlafaxine and bright light therapy reversed symptoms of depression, but adding bright light therapy may produce more rapid, stronger effects. Larger studies are needed to replicate these effects and determine whether they are long-lasting.