The curious case of penile vaginal intercourse and depression in women

I'm starting to worry that the last few Friday Weird Science write-ups by Scicurious (who seems, these days, to be the primary blogger at Neurotopia) have been of papers that I happen to have read. Just so you know: Thousands of papers are published per week across the diverse sciences, and although Scicurious tends to deal with life science and I tend to read life science, the chances of this particular harmonic convergence across bloggers regarding papers published over the last decade is statistically almost zero. More likely, Scicurious and I just have similar taste ... or lack thereof.

The latest paper written up by Sci is on the relationship between certain kinds of sexual intercourse and reduction of depression in women, suggested by a study by Gordon Gallup and others.

You should go read Scicurious's analysis first. Briefly, in this study, women who had regular sexual intercourse not using condoms were less depressed than women who had regular sexual intercourse using condoms. The study did in fact account for a number of different possibilities, and the authors did a pretty good job of eliminating many of the alternative explanations, though much of that is done with verbal reasoning rather than re-experiment with new design. The whole study is said to be preliminary, of course.

Scicurious, however, identifies a number of leftover questions, and I'd like to address them (somewhat unevenly and randomly):

1) You're telling me that "possible semen in the reproductive tract" with hormones absorbing through the vaginal wall, has a significant effect on how depressed women are, but oral contraceptives, which are taken every day and contain enough hormone to suppress ovulation, have NO significant effects on mood? This issue alone actually made me doubt the study. But perhaps they were looking at the wrong questions.

The original hypothesis proposed in 1986 by Ney was actually that prostaglandins affect mood. Gallup et al considered both prostaglandins and hormones. I would agree that oral contraceptives may be more significant with respect to hormones than vaginal deposits, but I would not assume that, nor would I assume that oral contraceptives have no effect on mood without experimental evidence designed to compare the two effects.

2) Sexually active women who do not use condoms are assumed to have semen in their reproductive tract after sex. I would highly doubt this, due to the popularity of "pulling out" and other methods sometimes used instead of condoms. I don't think a questionnaire could have adequately detected this.

I think the key word here is "popularity." I don't know what was going on in the Gallup study, but this particular variation in practice would not be something one could assume one way or another. What we do know is that variation in sexual practice of this type is great within and across American culture, changing across time sometimes quite quickly, and one cannot make this assumption. I would have thought Gallup would think of this, and I agree that it is not addressed in the study.

3) They state that females who didn't use condoms might be more likely to be in a committed relationship, but don't provide any data. I find this odd, it seems the questionnaire would certainly have asked that question. A committed relationship certainly could make a difference in mood.

This depends on number 2. It is logical, but not addressed adequately.

This was a preliminary study, but to my knowledge it has not been followed up, or if it was, not by Gallup (or at least not yet published). There have been a number of studies that have shown that women in sexual relationships have lower rates of depression or other affective state issues. One could infer that there is a sort of "ideal" (biosocially speaking) sexual relationship, and divergence from that (whatever it happens to be, contextually determined) may result in greater or lesser levels of something that can be measured psychometrically. One recent study (Miguel, 2008) looks at this issue from a Freudian perspective, and concludes that condoms, like masturbation, cause an increase in neurosis. Or something. (Journal of sexual medicine, 5(11) 2522-2532)

Interestingly the Gallup study has found its way into a few places as a citation indicating a relationship between sex and depression. In one Planned Parenthood document, the study is mentioned (uncritically) along with a number of other studies suggesting that sex is good for you, one way or another. No mention of the problem that Planned Parenthood may, through their condom distribution programs, be ruining it for everyone because of the depressive nature of this practice!!!!!

As Scicurious points out, regardless of if this study is valid or not, there are other factors related to depression that are surely more important. Like, I would suggest, overall physical activity levels.

So if you are depressed, get a membership to the nearest gym and start going on a regular basis. And who knows, you may meet someone nice! (Probably not, though.)

Gordon G. Gallup Jr., Rebecca L. Burch, Steven M. Platek (2002). Does semen have antidepressant properties? Archives of Sexual Behavior, 31 (3), 289-293 DOI: 10.1023/A:1015257004839