Researchers suggest men with low sexual desire may benefit from light therapy.
It is estimated that up to one quarter of men have a low sex drive - defined as lack of interest in sex. Anxiety, stress, depression, and other psychological factors can be causes of low sexual desire in men, as well as a reduction in the male sex hormone testosterone.
The new study - recently presented at the European College of Neuropsychopharmacology (ECNP) Congress in Vienna, Austria - found early morning exposure to bright light for 2 weeks increased men's testosterone levels, enhancing their sexual satisfaction.
Study leader Prof. Andrea Fagiolini, of the Department of Mental Health at the University of Siena in Italy, told Medical News Today that the findings came as no surprise.
"As a matter of fact, we already knew that sexual function increases during spring and summer and hypothesized that this might well have to do with the exposure to light," she said.
"Also, a previous study found a relationship between exposure to light therapy and increase in the levels of LH - a pituitary hormone called luteinizing hormone that raises testosterone levels in men."
Threefold increase in sexual satisfaction with light therapy
For their study, Prof. Fagiolini and colleagues decided to further investigate how bright light exposure influences men's testosterone levels, and what impact this might have on sexual desire.
The team recruited 38 men who had been diagnosed with either hypoactive sexual desire disorder (HSDD) or sexual arousal disorder; both conditions are characterized by low interest in sex.
Participants were divided into two groups; one group received 30-minute exposure to a specially adapted light box every morning for 2 weeks, while the other group - the control group - was exposed to a box that emitted much less light.
The men's testosterone levels and their interest in sex were assessed before and after the 2-week light box exposure.
Compared with the control group, men exposed to the active light treatment showed a significant increase in sexual satisfaction, the team reports.
"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," explains Prof. Fagiolini.
In comparison, the control group reported an average score of 2.7 following their 2-week treatment.
What is more, the researchers found men who received the active light therapy experienced an increase in testosterone levels over the 2-week period, from 2.3 nanograms per milliliter to 3.6 nanograms per milliliter. The control group showed no change in testosterone levels.
Increased testosterone may explain improved sexual satisfaction
The team says the increase in testosterone levels among men who received active light therapy likely explains the increase in sexual satisfaction.
Prof. Fagiolini notes that among individuals who live in the Northern hemisphere, testosterone levels naturally decline between November and April, increase steadily during spring and summer, and peak in October.
"You see the effect of this in reproductive rates, with the month of June showing the highest rate of conception," she adds. "The use of the light box really mimics what nature does."
The team proposes a number of ways by which bright light exposure may increase testosterone levels. For example, it may block pineal gland activity in the brain, which can increase testosterone production, and it may also increase LH levels - as noted in previous research.
While further studies in a larger population are warranted to better determine such mechanisms, Prof. Fagiolini and colleagues say their pilot study suggests light therapy may be a feasible nonpharmacological treatment approach for low sexual desire in men.
"We're not yet at the stage where we can recommend this as a clinical treatment. However, if this treatment can be shown to work in a larger study, then light therapy may offer a way forward. It's a small study, so for the moment we need to treat it with appropriate caution."
Prof. Andrea Fagiolini
Prof. Fagiolini told MNT that light box therapy could also help treat women with low sexual desire.
In particular, she cited the importance of an increase in LH as a result of bright light exposure, as low LH has been named as a contributor to low libido in women.
"LH may also trigger ovulation in women, which is also controlled by LH and which may be of interest for the fertility studies," she added.