Why is it that certain girls seem to take forever to get over breakups, ruminating, reminiscing, and obsessing over boys that have long since forgotten about them? Why do some women seem happiest when they are in relationships, and continually find themselves paired up anew within days of breaking up with a boyfriend?

In a study conducted in 2002 by Gordon Gallup and Rebecca Burch, who are both evolutionary psychologists at the State University of New York, the effect of sperm on female reproductive system was examined. The results were surprising—please allow me to apologize in advance for the slew of sleazy comments this will undoubtedly inspire amongst the lewder male readers.

The researchers examined 293 college students from the SUNY campus in Albany, and surveyed them comprehensively in regards to their sexual activity, including frequency of intercourse and condom usage. They wanted to see whether females who regularly had sperm introduced to their system were any different in terms of depression and relative happiness then those who didn’t. The usage of condoms was as an indirect measure of the presence of semen in the female reproductive tract, and the Beck Depression inventory was used to gauge their relative state of happiness. The researchers found that, surprisingly enough, “Not only were females who were having sex without condoms less depressed, but depressive symptoms and suicide attempts among females who used condoms were proportional to the consistency of condom use.” Moreover, sexually active females who didn’t use condoms seem to have developed something of an emotional dependency on sperm—according to Gallup and Burch’s report, the depression scores for these females “went up as the amount of time since their last sexual encounter increased.”

Why would women who don’t use condoms be less depressed and less likely to attempt suicide? Why would they be consistently more depressed as more time elapsed since their last “dosage” of semen?
According to the researchers, there are properties of semen that may help to alleviate depressive symptoms. As we all learned in high school biology, semen is not the same thing as sperm—less than 5% of semen is actually composed of sperm cells, and the count decreases with age. So what is the rest of the sticky mess made of? Many things, as it turns out. According to an article published by Jesse Bering in Scientific American, semen includes prolactin and thyrotopin—both natural antidepressants, estrone and oxytocin—which elevate mood, and even serotonin, a neurotransmitter well-known as an antidepressant and one of the chemicals most often manipulated in anti-depressant medications.

Taken as a whole, the data seems to suggest that women who are regularly inseminated are happier than women who aren’t, and that this is a factor of the chemical properties of sperm, which seem to be anti-depressant in nature. Though some will scoff and say that this is just a correlational study, that it might be the case that females who were more comfortable admitting their lack of condom use share personality traits that make them less susceptible to depression. However, the researchers anticipated this and accounted for these confounds. Firstly, they stressed that the survey was anonymous, so participants had little incentive to falsely represent their sexual behavior. Secondly, they statistically controlled for other possible influencing factors, including if the females were in relationship status and if so, what the duration of the relationship was. They also controlled for whether or not the participants used oral contraceptives. Lastly, in order to ascertain that the presence of semen, not the act of sex itself, was causing the difference in depression scores, the researchers did two things. They controlled for the frequency of sexual encounters, to make sure females who were having more sex were happier. They also compared the depression scores of females who were having regular sex with condoms to females who were not having sex at all, and found that the scores were no different, leading to the conclusion that “it is not sexual activity per se that antagonizes depression.”

Despite all this, one might argue that those females who regularly have condomless sex are those more inclined to high-risk behavior, and it may be something about this risky attitude which makes them less susceptible to depression. However, according to Tiffany Kary, writing for Psychology Today, “studies have found no correlation between high-risk sexual behavior and lower rates of depression.”

All things considered, it appears that there is a direct link between the amount of sperm in a woman’s body and her happiness. This does not mean everyone should throw away their condoms and have unprotected sex with everybody they cross paths with. But it may be something to consider if one is in a committed relationship, both partners are STI-free, and another reliable form of contraception is being used. Don’t kill me, Health Services, but it could be that girls are just happier with semen inside.