One might think that all kinds of sexual activity are alike in terms of sexual satisfaction, relationship satisfaction, mental health, and physiological effects. An orgasm is an orgasm is an orgasm. It turns out that this view is not supported by scientific research. Numerous studies have pointed to significant differences between, on the one hand, coitus (i.e. penile-vaginal intercourse or PVI) and, on the other hand, noncoital sexual activity such as oral sex, anal sex, and masturbation with or without a partner. Given that this research is relatively unknown among non-experts, it may be helpful to make this information more widely known.

In his Journal of Sex Medicine article, “The Relative Health Benefits of Different Sexual Activities,” Dr. Stuart Brody summarizes a number of studies stating that “[a] wide range of better psychological and physiological health indices are associated specifically with penile–vaginal intercourse. Other sexual activities have weaker, no, or (in the cases of masturbation and anal intercourse) inverse associations with health indices.” Multimethod evidence points to better psychological and physiological health benefits associated with coitus but not with other sexual behaviors.

Researchers also found differences in mental health satisfaction when comparing coitus with noncoital activities. Brody writes:

In a large representative sample of the Swedish population, PVI [penile-vaginal intercourse] frequency was a significant predictor of both men’s and women’s greater satisfaction with their mental health. In contrast, masturbation was inversely associated with mental health satisfaction in the multivariate analyses that controlled for other sexual behavior frequencies, and partnered sexual behaviors other than PVI [penile-vaginal intercourse] were uncorrelated with mental health satisfaction.

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Differences also existed regarding intimate relationship quality: “noncoital sex frequency was associated with less global relationship satisfaction, and noncoital partnered orgasm frequency was associated with less love.”

Likewise, researchers found differences with respect to rates of depression. In Brody’s words:

The association of masturbation with depression is unlikely to be a result of simply a lack of PVI, because more masturbation and less PVI make independent contributions to less satisfaction with relationships, sex life, life in general, and one’s mental health (the multivariate analyses also examined some partnered sexual activities other than PVI, and revealed that anal and oral sex frequency also have independent inverse associations with some of the satisfaction indices). It is likely that only unfettered, real PVI has important mood-enhancing benefits.

In the words of another study:

The findings demonstrate that sexual satisfaction is strongly related to PVI but not to other sexual behaviors (some of which are significantly inversely related to sexual satisfaction). A similar pattern applies to satisfaction with relationships, life in general, and one’s mental health. This evidence contrasts with assertions that masturbation and other sexual activities are as satisfying as PVI.

The difference may be due to greater release of prolactin which is associated with sexual satiety: “the prolactin rise after PVI orgasm is 400% greater than following masturbation orgasm.” Coitus and other kinds of sexual activity are not equivalent. “[S]atisfaction with sex life, life in general, sexual partnership, and mental health correlates directly with frequency of penile-vaginal intercourse (PVI) and inversely with frequency of both masturbation and partnered sexual activity excluding PVI (noncoital sex).”

One might be tempted to account for these psychological differences in satisfaction in terms of underlying differences in attitude among those who do them. People with more strict moral codes might feel guilty in doing noncoital sexual behaviors, and so might not experience the same psychological benefits that persons with less strict moral codes would experience. However, in a study entitled, yes, this is the real full title, “Satisfaction (Sexual, Life, Relationship, and Mental Health) Is Associated Directly with Penile-Vaginal Intercourse, but Inversely with Other Sexual Behavior Frequencies,” Brody and Rui Miguel Costa point out, “The exploratory finding that a rigid attitude toward variety in sexual activities was completely unrelated to the satisfaction indices suggests that it is indeed sexual behaviors (and the underlying psychosexual motives that guide them) that are related to satisfaction, rather than inflexible attitudes.”

In other words, it was not guilt about perceived failure to adhere to moral norms that undermined satisfaction. Those without so-called “rigid attitudes” had similar experiences as those with more traditional attitudes. Brody and Rui found that “[t]he results are consistent with evidence that specifically PVI frequency, rather than other sexual activities, is associated with sexual satisfaction, health, and well-being. Inverse associations between satisfaction and masturbation are not due simply to insufficient PVI.”

In addition to psychological benefits, physiological benefits are also associated with coitus but not other kinds of sexual behavior. Researchers found that, “specifically PVI but not other sexual behavior was associated with an important measure of better homeostasis, better parasympathetic tone, lower mortality risk, and better psychological function (including better relatedness).” The research suggests “not only that it is specifically PVI (rather than other sexual behaviors) that is associated with optimal cardiovascular ‘protection’ from stress, but also that the benefits are not simply due to having a partner.” Similarly, Brody cites studies showing the benefits of coitus but not other sexual activities in reducing the likelihood of prostate cancer, breast cancer, hot flash symptoms, pre-eclampsia, low sperm count, and high blood pressure.

Might all these associations be mere associations? Dying in motorcycle accidents is merely associated with and is not caused by wearing leather jackets. Or is it that the case that noncoital sexual activity actually causes the adverse effects found in the research? It may be impossible ever to know with certainty without control groups and placebos of various kinds of sexual actions. Nevertheless, as Randall Munroe once said, “correlation doesn’t imply causation, but it does waggle its eyebrows suggestively and gesture furtively while mouthing ‘look over there.’”  What we know about addiction is learned not through controlled laboratory experiments but through the extensive empirical evidence of associations and the ruling out of possible confounding variables. We can, presumably, learn about the empirical effects of various kinds of sexual activities in a similar way.

Indeed, the evidence suggests that coitus produces health benefits: “It is specifically PVI, competently performed and sensitively experienced, that is associated with . . . and produces . . . aspects of better mental and physical health. This is not the case for other sexual behaviors (masturbation and anal intercourse are associated with poorer health indices, effects not attributable simply to lack of PVI).”

What might account for these differences? A number of mechanisms might account for the differences between coitus and noncoital sexual behavior. For example, Brody writes:

Evolutionary pressures strongly reward behaviors and mutations even slightly associated with increased likelihood of gene propagation. The difference between PVI and other sexual behaviors is not slight. The mechanisms by which such evolutionarily mandated rewards might operate range from direct physiological mechanisms (responding favorably to PVI but neutrally or unfavorably to other sexual activities) to mechanisms secondary to the evolutionary behavioral ‘success’ of specifically PVI being rewarded by better physical and mental health (and perhaps the evolutionary behavioral failure of other sexual activities such as masturbation being punished by poorer physical and mental health).

To conclude, here’s what the science suggests:

Based upon a broad range of methods, samples, and measures, the research findings are remarkably consistent in demonstrating that one sexual activity (PVI and the orgasmic response to it) is associated with, and in some cases, causes processes associated with better psychological and physical functioning. Other sexual behaviors (including when PVI is impaired, as with condoms or distraction away from the penile–vaginal sensations) are unassociated, or in some cases (such as masturbation and anal intercourse) inversely associated with better psychological and physical functioning.

A number of other studies point to similar conclusions.

Both the natural law and the Catholic Church teach that sexual activity should be of a kind that is “of itself suited to procreating human life.” The empirical evidence suggests that following this teaching is associated with significant psychological and physical benefits and that violating this teaching is associated with significant psychological and physical harms.