Liam Davenport

September 20, 2016

VIENNA — Light therapy of the kind used to treat seasonal affective disorder may significantly improve sexual satisfaction in men with low sexual desire and arousal after just 2 weeks of treatment, new research shows.

A study presented here at the 29th European College of Neuropsychopharmacology (ECNP) Congress showed that daily exposure to a light box on waking significantly increased blood testosterone levels, which may explain the impact of the treatment on sexual satisfaction.

Study investigator Andrea Fagiolini, MD, chairman, Division of Psychiatry, University of Siena School of Medicine, Italy, told Medscape Medical News that although it cannot be said at this time that light therapy "will replace Viagra, we did see a very strong effect."

The investigators plan to repeat the study with larger numbers of patients.

"The good thing is that it's basically safe. Unless people have some eye problems, it's really unlikely that this gives problems, whereas any medication has much more problems in terms of side effects and dangerous interactions with other medications," he said.

"Even if I would recommend not to use it until we have results from larger trials, if somebody wants to use it, it's not going to give too many problems, because it is a treatment that is already used for another disorder, and we know it's pretty safe," Dr Fagiolini added.

To examine the impact of light treatment on sexual function, the researchers studied 38 men who had been referred to the University of Siena with a diagnosis of primary hypoactive sexual desire or sexual arousal disorder.

The patients were randomly allocated to receive either active light treatment or placebo light treatment. Active light treatment consisted of daily 30-minute exposure on waking to a white fluorescent light box fitted with an ultraviolet filter that was rated at 10,000 lux at a distance of 1 meter from the cornea.

Placebo light treatment was the same, but with the addition of a neutral density filter to reduce the light exposure to 100 lux.

Participants were assessed before and after 2 weeks of treatment with the Structured Clinical Interview for DSM-5 sexual disorders and a self-administered rating scale of the level of sexual satisfaction. Blood samples were taken at baseline and at 2 weeks to determine testosterone levels.

After 2 weeks of therapy, individuals who received active light treatment had experienced significant improvements in sexual satisfaction compared with those receiving placebo light treatment (P < .05).

"Before treatment, both groups averaged a sexual satisfaction score of around 2 out of 10, but after treatment, the group exposed to the bright light was scoring sexual satisfaction scores of around 6.3, a more than threefold increase on the scale we used. In contrast, the control group only showed an average score of around 2.7 after treatment," said Dr Fagiolini.

At baseline, the mean testosterone level was 2.1 ± 1.3 ng/ml in the active therapy group and 2.3 ± 0.6 ng/ml in the placebo group. After treatment, testosterone levels had risen significantly in the active therapy group, to a mean of 3.6 ± 1.1 ng/ml (P < .05). There were no significant changes in the placebo group.

"The increased levels of testosterone explain the greater reported sexual satisfaction. In the Northern hemisphere, the body's testosterone production naturally declines from November through April and then rises steadily through the spring and summer, with a peak in October," said Dr Fagiolini.

"You see the effect of this in reproductive rates, with the month of June showing the highest rate of conception. The use of the light box really mimics what nature does. We believe that there may be several explanations to explain the underlying mechanism. For instance, light therapy inhibits the pineal gland in the center of the brain, and this may allow the production of more testosterone, and there are probably other hormonal effects."

Cautionary Note

Commenting on the findings, Eduard Vieta, MD, PhD, chair of the Department of Psychiatry and Psychology at the University of Barcelona Hospital Clinic, Spain, who is treasurer of the ECNP, commented that "light therapy has been used successfully in the past to treat some forms of depression, and this study suggests now that it may also work to treat low sexual desire in men. The mechanism of action appears to be related to the increase of testosterone levels," he said.

However, Dr Vieta sounded a note of caution over its use at this stage for the treatment of low sexual desire.

"Before this kind of treatment, which is likely to be better tolerated than pharmacological therapy, gets ready for routine use, there are many steps to be implemented, including replication of the results in a larger, independent study and verifying whether the results are long-lasting and not just short-term," he said.

The study was funded by the University of Siena. The investigators and Dr Vieta have disclosed no relevant financial relationships.

29th European College of Neuropsychopharmacology (ECNP) Congress. Abstract P.4.b.010. Presented September 19, 2016.


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