Although we are still far from knowing exactly where and how the pineal suppressive role is exerted, the fact that the gland exerts an inhibitory function on the reproductive axis is widely accepted. In fact, the pineal seems to exert its hormonal effect at different levels of the reproductive axis, both at the hypothalamic-pituitary level and at the gonadal level, where melatonin receptors have also been found.
Furthermore, melatonin appears to increase prolactin secretion, which may contribute to sexual dysfunction. Based on the observations mentioned above a group of italian investigators hypothesized that an inhibition of pineal gland activity via a treatment with bright light could favorably influence sexual function and pilottested the usefulness of bright light therapy in a small sample of 9 male patients with nonorganic sexual dysfunction.
Subjects (age 39–60) were consecutively recruited in the outpatient clinic of the Urology Department of the University of Siena Medical Center on the basis of a diagnosis of primary (i.e. not due to another illness or to a medication or a drug of abuse) hypoactive sexual desire disorder (HSDD, n = 2), sexual arousal disorder (SAD, n = 6), and orgasmic disorder (OD, n = 1) and the absence of a mood disorder, as assessed via the Mini International Neuropsychiatric Interview. Subjects were randomly assigned to active light treatment (ALT) or placebo light treatment (L-PBO) and assessed at baseline and after 2 weeks of ALT/L-PBO treatment via the Structured Clinical Interview for DSM-IV-Sexual Disorders (SCID-S) and via a sexual satisfaction self-report, which asked them to rate on a scale from 1 to 10 their level of sexual satisfaction.
The ALT consisted of daily exposure to a white fluorescent light box (Super-Lite 3S, fitted with an ultraviolet filter and rated at 10,000 lx at a distance of 1 m from screen to cornea) for 30 min as soon as possible after awakening, between 7.00 a.m. and 8.00 a.m. The L-PBO was an identical light box fitted with a neutral density gel filter to reduce light exposure to 100 lx. After 2 weeks of treatment, 3 of the 5 patients randomized to ALT no longer met the SCID-S criteria for a sexual disorder whereas the sexual disorder was still present in all the 4 patients in the L-PBO group. A significant (p = 0.001) improvement in sexual satisfaction was observed in the ALT group, whereas no improvement was observed in the L-PBO group (p =0.39).
The findings of this study suggest a potentially favorable effect of bright light therapy on primary sexual dysfunctions. A larger study is now needed to confirm these preliminary results and to test whether bright light therapy may be of help for the treatment of sexual dysfunctions that are associated with certain psychiatric illnesses, such as major depressive disorder, or with medications that are prescribed to treat those illnesses.
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