Study reveals sex differences in brain responses to low sexual desire

In a study recently published in the journal Scientific reportsResearchers examined the neurofunctional determinants of Hypoactive Sexual Desire Disorder (HDSS) in women and men. The condition, colloquially referred to as “distressingly low sexual desire,” has previously been studied in women, but never in men. In the present study, researchers used functional magnetic resonance imaging (fMRI) coupled with psychometric questionnaires to assess men’s and women’s neurofunctional responses to sexual and non-sexual video presentations.

This study found that women with shockingly low sexual desire follow the “top-down” theory of the HDSS, which suggests that hyperactivity in higher-level cognitive brain regions suppresses lower-level sexual brain regions. In contrast, this neurofunctional pattern was not observed in men, highlighting a sexual dimorphism in the way male and female brains process sexual stimuli. While this study is unable to elucidate the cognitive mechanisms underlying HDSS in men, it highlights the need for additional male HDSS research and suggests that clinically low sexual desire interventions in women may not contribute to desired outcomes lead their male colleagues.

Women with HSDD have greater limbic activation for sexual videos than men. (A) The female and (b) Average results of the male HSDD group showing activation (red/yellow) and deactivation (blue-green) of the brain for sexual purposes compared to control (exercise) videos. (C) Brain regions that are more sexually activated in women (compared to men) compared to control videos are shown in purple. Brain regions that are more sexually activated in men (compared to women) compared to control videos are shown in green. Results are cluster corrected and have a threshold of Z = 2.3, P < 0.05, N = 64 (32 women, 32 men). Study: Women with HSDD have greater limbic activation for sexual videos than men. (A) The female and (b) Average results of the male HSDD group showing activation (red/yellow) and deactivation (blue-green) of the brain for sexual purposes compared to control (exercise) videos. (C) Brain regions that are more sexually activated in women (compared to men) compared to control videos are shown in purple. Brain regions that are more sexually activated in men (compared to women) compared to control videos are shown in green. Results are cluster corrected and have a threshold of Z = 2.3, P < 0.05, N = 64 (32 women, 32 men). Study: Women and men with distressingly low sexual desire exhibit sexually dimorphic brain processing

What is HDSS and what do we know about the disease?

The Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Revised (DSM-IV-TR) defines Hypoactive Sexual Desire Disorder (HSDD) as “persistent sexual fantasies and desires for sexual activity that cause significant distress or interpersonal difficulties.” Commonly referred to as “disturbingly low sexual desire,” “hyposexuality,” or “inhibited sexual desire,” HDSS is a sexual dysfunction whose symptoms include a significant lack of sexual fantasies and arousal even in sexually active men and women. Given the significant social and interpersonal anxiety that HDSS causes, the disorder is often accompanied by depression and similar emotional disorders.

HDSS was first identified in 1980 (DSM-III) and officially defined in 1987 (DSM-III-R). HDSS is a clinically distinct condition that is distinct from conditions such as asexuality and erectile dysfunction, sex hormone levels, or other diseases such as cancer, diabetes and multiple sclerosis. Despite its relatively new description, HDSS is now one of the most common sexual disorders worldwide, affecting an estimated 10% of women and 8% of men. Worryingly, given the social stigma associated with the condition, these figures are believed to be greatly underestimated, highlighting the need for interventions to address the impact of the neurofunctional condition on quality of life (QoL).

Unfortunately, despite limited research on HDSS to date, the available scientific literature on this topic is almost exclusively aimed at women, and there has only been one study on men, albeit using controversial methods. This disparity in research is reflected in treatment options: Two medically approved procedures are available for American women, but none are available for American men. Notably, the vast majority of HDSS incidents in men are misdiagnosed as erectile dysfunction, exacerbating the burden and mental health impact of the condition.

About the study

In the present study, researchers aim to use functional magnetic resonance imaging (fMRI) in conjunction with several psychometric questionnaires to assess the neurofunctional responses of men and women with HDSS to sexual and non-sexual stimuli (here video presentations – visual sexual stimuli). . The study cohort consisted of men and women with clinically confirmed HDSS (ICD-11) recruited via advertisements across London (print and online media). Participant screening consisted of a telephone interview followed by an in-person medical examination (blood and questionnaire) to differentiate between acquired and generalized HDSS. To avoid confounding due to pre-existing clinical illnesses, individuals with a history of psychiatric illness or those currently taking medication were excluded from the study.

“…participants had to live in a stable, communicative and monogamous relationship for >6 months. Participants were excluded if they had a history of unresolved sexual trauma, abuse, or aggression, had taken medications (prescription or over-the-counter) or herbal preparations to increase sexual desire, arousal, or performance, or had a contraindication to an MRI scan.”

The experimental intervention involved the presentation of 20-second silent sex videos (cases) alternating with neutral, non-sexual exercise videos (controls) over a 12-minute standard validated (using Likert scale) block design. Participants were required to complete a Sexual Desire and Arousal Inventory (SADI) questionnaire immediately before and after the experimental intervention, measuring 54 descriptors in the domains of “evaluative,” “negative,” “physiological,” and “motivational.” During the experimental intervention, participants underwent concurrent fMRI and pulse oximeter assessment.

Data processing included the correlations between questionnaire results and fMRI stimulus images, overlaps between male and female activation patterns (via Dice coefficients) in sexual and non-sexual visual stimuli, and analysis of regions of interest (ROIs) of the brain, particularly those corresponding to the sexual neural network (amygdala, hypothalamus, insula, precentral gyrus, striatum and thalamus).

Study results and conclusions

After the screening process, the study sample group included 32 men and 32 women with clinically confirmed HDSS. While the men were, on average, nine years older than their female counterparts, the Dice coefficient results suggest that age did not skew the study results. In addition, 20 “healthy” men and women were recruited to validate the differences between sexual and non-sexual stimuli and to establish bases for response patterns to neural activation stimuli.

“The results are somewhat consistent with previous research in individuals with normal sexual desire, suggesting that women and men have similar general activation patterns to visual sexual stimuli.” However, notable differences in limbic activation were observed in women and men with HSDD Brain regions observed, particularly the hypothalamus, amygdala and thalamus, which are key structures related to emotional processing and sexual motivation.”

The present study highlights that the sexual neural network in women with HDSS shows activation during the presentation of sexual stimuli; However, these “lower” neurofunctional centers (limbic regions) are masked by the simultaneous activation of higher-level cortical regions, supporting the “top-down” inhibition hypothesis proposed by Cacioppo. In contrast, men with HDSS did not show activation of the sexual neural network, suggesting that visual sexual cues are not effectively relayed to emotional centers associated with sexual responses. This study is the first scientific work to elucidate the sexual dimorphism between male and female neurofunctional HDSS. It highlights the need for additional research, particularly in men, before effective therapeutic interventions against the condition can be formulated.