A recent study published in Scientific Reports has shed light on the distinct neural mechanisms underlying hypoactive sexual desire disorder (HSDD) in men and women. Researchers found significant differences in brain activity between the sexes, offering new insights into the condition and paving the way for more targeted treatments.
Sexual desire is a fundamental aspect of human life, crucial for emotional connection, intimacy, and overall well-being. HSDD, characterized by a persistent lack of sexual interest causing significant distress, affects about 10% of women and 8% of men. Despite its prevalence, the disorder is relatively under-studied, particularly in men. Current treatments are only available for women in the United States, highlighting the need for better diagnostic and therapeutic options for men.
The prevailing theory of HSDD, developed from studies on women, suggests that excessive activation of higher-level brain regions responsible for introspection and self-monitoring leads to reduced activity in lower-level regions involved in emotional and sexual processing. However, this theory does not account for men with HSDD. To address this gap, the researchers aimed to directly compare the neural mechanisms of HSDD in both sexes using functional magnetic resonance imaging (fMRI).
“We are interested in better understanding the brain regions disrupted in individuals with distressing low sexual desire,” said study author Alexander Comninos, a professor at Imperial College Healthcare NHS Trust and Imperial College London. “A better understanding will lead to better treatments as in men there are no licensed treatments and in women the treatments (only available in North America) have limited efficacy and carry unwanted side-effects such as drowsiness, nausea, and syncope as well as interactions with alcohol.”
For their new study, the researchers recruited 32 premenopausal women and 32 men, all diagnosed with HSDD and free of psychiatric illnesses and medications. The participants, who were in stable relationships, underwent a detailed screening process, including medical history, psychometric questionnaires, and blood tests to ensure normal health and exclude endocrine abnormalities.
During the study, participants watched sexual and control (exercise) videos while undergoing fMRI scans. The sexual videos were selected based on ratings from focus groups of healthy individuals to ensure they were arousing. After each video, participants rated their arousal level. The fMRI scans measured brain activity, focusing on regions associated with sexual and emotional processing.
The study revealed both similarities and differences in brain activation patterns between men and women with HSDD. Both sexes showed similar general patterns of activation in response to sexual stimuli, with increased activity in regions like the striatum, visual cortex, cerebellum, and anterior cingulate cortex. These areas are known to be involved in sexual processing.
However, significant differences emerged in the magnitude and specific regions of activation. Women with HSDD exhibited greater activation in limbic regions such as the amygdala, striatum, and thalamus, which are associated with emotional processing and sexual motivation. In contrast, men showed greater activation in the visual cortex, indicating a heightened sensitivity to visual sexual cues.
These findings suggest that while women with HSDD might experience more emotional and motivational disturbances related to sexual desire, men might have a disruption in processing visual sexual cues into emotional responses. This difference points to a potential disconnect between visual and emotional systems in men with HSDD.
“In this study, we compared the brain responses to erotic videos in women and men with distressing low sexual desire,” Comninos told PsyPost. “Broadly speaking, the brain regions disrupted in distressing low sexual desire appear similar in women and men. However, our data suggest some interesting sex differences. In women, the predominant finding is a top-down inhibition of the sexual response, consistent with the previous literature in women. This was demonstrated by the hyperactive frontal gyrus and associations with lower sexual function on psychometric testing in women.”
“However, in men we observed increased activation in the visual cortex (compared to women), suggesting that visual attention to the erotic cues is not effectively relayed to emotional centres involved in sexual responses. Collectively, these data have clinical implications for the development of new diagnostic and therapeutic approaches to women and men seeking help for distressing low sexual desire.”
But, as with any study, the new research has some caveats. The lack of a control group with normal sexual desire limits the ability to fully understand the differences between individuals with and without HSDD.
Future research should include a control group to compare brain activity patterns directly. Investigating therapies that target specific brain regions or connectivity patterns could also lead to more effective treatments. For instance, therapies enhancing the connection between visual and emotional centers in the brain might benefit men with HSDD, while approaches reducing hyperactivity in higher cortical regions or boosting activation in limbic regions could be effective for women.
“Our primary goal is to develop much-needed better-tolerated and effective treatments for individuals seeking help for their distressing low sexual desire,” Comninos said. “We have previously shown that kisspeptin, a reproductive protein, when administered can improve sexual brain processing in both women and men with distressing low sexual desire. In fact, in men with low sexual desire it even appears to even have a pro-erectile effect from our studies and is very well-tolerated.”
“The current study advances our understanding of the core neural disruptions in low sexual desire and gives us confidence that kisspeptin may indeed have therapeutic potential in both women and men as their disruptions are broadly similar. However, these are early days and we continue to work tirelessly on it as funding allows, as it is a hugely significant issue for many people, negatively affecting their quality of life, relationships and in some cases fertility.”
The study, “Women and men with distressing low sexual desire exhibit sexually dimorphic brain processing,” was authored by Natalie Ertl, Edouard G. Mills, Matthew B. Wall, Layla Thurston, Lisa Yang, Sofiya Suladze, Tia Hunjan, Maria Phylactou, Bijal Patel, Paul A. Bassett, Jonathan Howard, Eugenii A. Rabiner, Ali Abbara, David Goldmeier, Alexander N. Comninos, and Waljit S. Dhillo.
