New York Times Magazine published an article
discussing the ongoing clinical trials of a unique new drug that caught the
interest of Emory University neuroscience graduate student Mallory Bowers. The drug, dubbed “Lybrido”, was being tested
for its ability to improve sexual desire in women. However, Lybrido is not just a female
Viagra-like formulation. That is
apparently one part of it but the other, perhaps more surprising part, is the
pill’s testosterone coating that is designed to melt away immediately in the
mouth. To better understand how testosterone (T) could modulate female desire,
and to discuss the neuroethical implications of pharmaceutically targeting it,
Ms. Bowers chose a recent paper in the Journal of Sex Research by Goldey et al. entitled “Sexual Fantasies and
Gender/Sex: A Multimethod Approach with Quantitative Content Analysis and
Hormonal Responses” for the second Neuroethics Journal Club of the year.
In the present study, Sari van Anders’s group at the
University of Michigan designed experiments to dissect the gender differences
in testosterone’s role in sexual behavior, which has not been well-understood. Although men have much higher levels of T, it
is secreted by the adrenal glands in both men and women. Similarly, men have comparable levels of
circulating estradiol (E2) to women despite that hormone being
typically associated with the female reproductive cycle. However, according to van Anders, the
available evidence suggests that while E2 and T are both associated
with intimacy, E2 is more related to nurturing behavior whereas T is
more closely linked to explicit sexuality. In this study, van Anders’s group explored
these potential differences by quantifying the nurturing and explicit sexual
content of volunteers’ fantasies accompanied by hormonal measures.
The Steroid/Peptide Theory of Social Bonds (S/P Theory), as
presented by van Anders in a recent review1,
is explained through an evolutionary perspective: explicit sexual contexts,
which support reproduction, increase T but nurturant contexts, which support
parent-offspring bonds perhaps at the energetic expense of further
reproduction, decrease T (in men).
However, van Anders argues that social contexts strongly impact T
responses as well: men are socially discouraged from excessive nurturing and
women are socially discouraged from being overly sexual. It is thought that perhaps due to their lower
baseline levels, women may be more sensitive to small changes in circulating
levels of T2, and van Anders
hypothesized that levels of T might be differentially modulated by the content
of sexual fantasies in men and women.
In previous studies, T has been observed to increase most
consistently in the context of sexuality for physical pleasure in men and women,
but nurturing behavior has been associated with lower T in men3. The same group found that sexual fantasy
increases T in women4 but not men5 and the authors
reasoned that sexual fantasies likely include thoughts of nurturing behaviors
in addition to those of an explicitly sexual nature which, according to S/P
Theory, would give a mixed signal in terms of T and could explain gender
differences. These observations and
others have led van Anders to propose S/P Theory to better explain how these
hormones, in conjunction with the neuropeptides oxytocin and vasopressin,
influence social and sexual behaviors in men and women.
 |
| The Steroid/Peptide Theory of Social Bonds (van Anders et al.) |
The study by Goldey et al. was designed to determine whether
fantasy content differs between genders and if the frequency of nurturing or
sexual content predicts hormonal responses. The authors report a significant
negative correlation specifically in men between change in T and frequency of
nurturant content in fantasies. Essentially, the men who included less
nurturing images in their fantasies had larger increases in salivary T during
the test. This was an expected result
and supports van Anders’s S/P Theory.
However, the group also unexpectedly found no overall difference in the
amount of explicit sexual or nurturing content between male and female
fantasies. The authors, as well as our
journal club group, thought that this might result from the volunteers being
mostly young undergraduate psychology students who are not necessarily
representative of even Western society at-large. Moreover, it was suggested that relationship
status and history could strongly impact fantasy content and conceivably the
hormonal response to it. An analysis of
any relationship between these variables might have been very interesting
though the sample size in this particular study might not have provided enough
statistical power to detect differences.
So how does an individual’s hormonal profile impact fantasy
content and how do fantasies affect hormonal fluctuations? There is still quite a lot to learn, but as exemplified by the makers of Lybrido and other potential female
libido-boosters, the impact of this research reaches well beyond academic
journal clubs and the neuroethical considerations are significant. Another approach that this group could have
taken – which likely would have extended these findings – would be to dose
participants with placebo, T, or E2 and then quantify sexual fantasy
narratives under each of these three conditions. It would be very interesting to see if T and
E2 differentially modulate narrative content in men and women but,
even if that is the case, should this be a pharmaceutical target? Both Viagra and Lybrido essentially aim for
the same effect but the latter affects brain function as well as blood
flow. But is lack of sexual desire
really a mood disorder or, is any uneasiness about the prospect of a female
libido-enhancer simply the result of our society being less comfortable with
women wanting to improve their sex lives?
These questions are clearly beyond the scope of Goldey’s paper but may
be important to discuss for future basic science and clinical research.
An innovative aspect of van Anders’s study was the
integration of individual narratives as well as biological measures. As the authors point out, biological measures
are often thought to be more valid than qualitative analyses. In this case the narratives provided a very
useful context to understand the hormonal data and this approach will likely be
useful in future studies. To some, the
idea of a single pill to modulate a complex mood may be offensively
reductionist but van Anders’s multi-method approach offers the possibility to
better understand the nuances of the reciprocal relationship between hormonal
fluctuations and sexual attitudes. One
near-certainty is that a drug like Lybrido will reach the market soon and so in
the meantime, and beyond, studies and discussions such as these should
continue.
For more on Dr. van Anders check out this 2012 interview
on The Neuroethics Blog.
References
van Anders, S. M., Goldey, K. L. & Kuo, P. X. The Steroid/Peptide Theory of
Social Bonds: integrating testosterone and peptide responses for classifying
social behavioral contexts. Psychoneuroendocrinology
36, 1265-1275,
doi:10.1016/j.psyneuen.2011.06.001 (2011).
Sherwin,
B. B. A Comparative-Analysis of the Role of Androgen in Human Male and Female
Sexual Behavior - Behavioral Specificity, Critical Thresholds, and Sensitivity.
Psychobiology 16, 416-425 (1988).
S.M. van
Anders, K. L. G., P.X. Kuo. The steroid/peptide theory of social bonds:
Integrating testosterone and peptide responses for classifying social
behavioral contexts. . Psychoneuroendocrinology,
1265-1275 (2011).
Goldey,
K. L. & van Anders, S. M. Sexy thoughts: effects of sexual cognitions on
testosterone, cortisol, and arousal in women. Hormones and behavior 59,
754-764, doi:10.1016/j.yhbeh.2010.12.005 (2011).
Goldey,
K. L. & van Anders, S. M. Sexual thoughts: links to testosterone and
cortisol in men. Archives of sexual
behavior 41, 1461-1470,
doi:10.1007/s10508-011-9858-6 (2012).
Want to cite this post?
Ryan, P. (2013). Neuroethics Journal Club: Sexual Fantasies and Gender/Sex. Retrieved on
, from http://www.theneuroethicsblog.com/2013/11/neuroethics-journal-club-sexual.html
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