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Bright light boosts testosterone in men with low libido, study says

Bright light boosts testosterone in men with low libido, study says
A man sits in front of a light therapy box, a full spectrum light box which mimics the sun. A new study suggests light therapy can boost testosterone in men with low libido. (Mint Images - Paul Edmondson via Getty)

For men whose sex drive has stalled, Italian researchers have found in a small study that early morning exposure to bright light – a treatment widely used for seasonal depression --  revs up testosterone production and boosts sexual function and satisfaction.

In a pilot trial that recruited 38 men diagnosed with problems of sexual desire and arousal, researchers at Italy's University of Siena found that after two weeks, participants who spent a half-hour each morning in front of specially designed light box experienced increases in testosterone and a three-fold improvement in sexual satisfaction. Participants who were randomly assigned to get a placebo treatment – a light box that delivered a level of light only 1% as intense – saw no significant change on either measure.

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In addition to offering men a potential remedy for flagging sexual desire, the findings of the preliminary trial add evidence to the surmise that sunlight plays a key role in promoting testosterone production and sexual desire in men.

In the Northern Hemisphere, past research has shown that spring and summer, with their bright sunshine, nudge testosterone production progressively upward, yielding a pleasant autumn surprise — a peak of testosterone production, and with it, surging sexual interest and arousal right about now. But then, as winter's gloom sets in, comes a man's long winter of discontent: Between November and April, men in the Northern Hemisphere typically experience a slump in testosterone production. Reproduction rates generally rise and fall with this hormonal ebb and flow.

"The use of the light box really mimics what nature does," said Andrea Fagiolini, a professor of psychiatry at the University of Siena and lead author of the new study.

Presenting his group's findings Monday at the European College of Neuropsychopharmacology Congress in Vienna, Fagiolini said that a blast of bright light in the morning appears to suppress a man's production of melatonin, which acts as a brake on testosterone production. As testosterone production increased in response, men reported greater interest in sex.

Light boxes have long been used to battle seasonal affective disorder, a condition in which patients  routinely lapse into depressive episodes during the winter. The boxes should have a filter to minimize a user's exposure to ultraviolet rays, and people who've had past or current eye problems such as glaucoma, cataracts or eye damage from diabetes should get advice from an eye doctor before starting light therapy.

Professor Eduard Vieta, chairman of the University of Barcelona Hospital Clinic's Department of Psychiatry and Psychology, observed that for many men, light treatment would be preferable to taking prescription medications, which include testosterone supplements. But he said the value of light therapy for sexual problems still needs to be borne out in a larger, independent study, and researchers need to verify whether the results are "not just short-term."

Follow me on Twitter @LATMelissaHealy and "like" Los Angeles Times Science & Health on Facebook.

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