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Why Does Sex Make Men Sleepy?

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Alfred Kinsey, biologist, pioneering sex researcher and founder of the Institute for Sex Research at Indiana University*, once wrote that "a marked quiescence of the total body is the most widely recognized outcome of orgasm," more noticeably among males. Why is that?

Let's get the obvious reasons out of the way first. Sex often, though not always, happens at night in a bed and is physically exhausting. If you're tired to begin with, all that physical exertion only adds to it, and since you're already in bed, it's only natural to be sleepy. Compounding this is the fact that sex dominates your attention when you're having it (and sometimes when you're not), so you don't pay attention to your breathing and wind up breathing shallowly and holding your breath pretty often. These aren't really the sorts of things you want to do during vigorous exercise, as they lead to oxygen deprivation and—all together now—sleepiness.

There's also the biochemistry of the orgasm to consider.

After sex, a man's brain releases a slew of hormones and neurotransmitters. Some of them, like prolactin, oxytocin and vasopressin, have been linked to sleep as well as sex. Prolactin plays a role in sexual satisfaction by counteracting the effects of dopamine** (which is responsible for sexual arousal). It's also been shown that the artificial delaying of an REM sleep period disrupts the rhythm of prolactin release, and that REM sleep is reduced in mice with prolactin deficiencies. Oxytocin and vasopressin have also both been implicated in the body's regulation of sleep cycles. While none of these chemicals are fully understood and their links to sleep aren't concrete, the circumstantial evidence suggests that they may play a part in pulling you off to a post-coital snooze.

What About the Ladies?

The phenomena of men falling asleep soon after sex is a little more well established than women doing the same—at least in that people notice it enough to make jokes about it on sitcoms, and write in to mental_floss asking about it. While I haven't been able to find any science-backed evidence that post-sex sleepiness definitively affects men more than women, there are a few hypotheses floating around as to why it seems that way. In their 2006 book Why Do Men Fall Asleep After Sex?, Mark Leyner and Billy Goldberg, M.D. suggest that exertion during sex depletes the muscles of energy-producing glycogen. Because men usually have more muscle mass, they get more tired. And it's entirely possible that women get just as sleepy, just as fast as men do after orgasm, but women simply have orgasms during sex less often than men do.

*Kinsey left his mark on a different field earlier in his career: entomology. He did his doctoral thesis on gall wasps and researched and published papers about them at the American Museum of Natural History in New York. Of the 18 million+ insects in the museum's collections, about 5 million are gall wasps that Kinsey collected. In return for his collection, Kinsey received $400 and a lifetime membership to the Museum.

**The hormone may also mediate the "sexual refractory period," or the recovery phase after an orgasm during which a man cannot have additional orgasms or achieve an erection.

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Women Suffer Worse Migraines Than Men. Now Scientists Think They Know Why
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Migraines are one of medicine's most frustrating mysteries, both causes and treatments. Now researchers believe they've solved one part of the puzzle: a protein affected by fluctuating estrogen levels may explain why more women suffer from migraines than men.

Migraines are the third most common illness in the world, affecting more than 1 in 10 people. Some 75 percent of sufferers are women, who also experience them more frequently and more intensely, and don't respond as well to drug treatments as men do.

At this year's Experimental Biology meeting in San Diego, researcher Emily Galloway presented new findings on the connection between the protein NHE1 and the development of migraine headaches. NHE1 regulates the transfer of protons and sodium ions across cell membranes, including the membranes that separate incoming blood flow from the brain.

When NHE1 levels are low or the molecule isn't working as it's supposed to, migraine-level head pain can ensue. And because irregular NHE1 disrupts the flow of protons and sodium ions to the brain, medications like pain killers have trouble crossing the blood-brain barrier as well. This may explain why the condition is so hard to treat.

When the researchers analyzed NHE1 levels in the brains of male and female lab rats, the researchers found them to be four times higher in the males than in the females. Additionally, when estrogen levels were highest in the female specimens, NHE1 levels in the blood vessels of their brains were at their lowest.

Previous research had implicated fluctuating estrogen levels in migraines, but the mechanism behind it has remained elusive. The new finding could change the way migraines are studied and treated in the future, which is especially important considering that most migraine studies have focused on male animal subjects.

"Conducting research on the molecular mechanisms behind migraine is the first step in creating more targeted drugs to treat this condition, for men and women," Galloway said in a press statement. "Knowledge gained from this work could lead to relief for millions of those who suffer from migraines and identify individuals who may have better responses to specific therapies."

The new research is part of a broader effort to build a molecular map of the relationship between sex hormones and NHE1 expression. The next step is testing drugs that regulate these hormones to see how they affect NHE1 levels in the brain.

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The Surprising Link Between Language and Depression
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Skim through the poems of Sylvia Plath, the lyrics of Kurt Cobain, or posts on an internet forum dedicated to depression, and you'll probably start to see some commonalities. That's because there's a particular way that people with clinical depression communicate, whether they're speaking or writing, and psychologists believe they now understand the link between the two.

According to a recent study published in Clinical Psychological Science, there are certain "markers" in a person's parlance that may point to symptoms of clinical depression. Researchers used automated text analysis methods to comb through large quantities of posts in 63 internet forums with more than 6400 members, searching for certain words and phrases. They also noted average sentence length, grammatical patterns, and other factors.

What researchers found was that a person's use (or overuse) of first-person pronouns can provide some insight into the state of their mental health. People with clinical depression tend to use more first-person singular pronouns, such as "I" and "me," and fewer third-person pronouns, like "they," "he," or "she." As Mohammed Al-Mosaiwi, a Ph.D. candidate in psychology at the University of Reading and the head of the study, writes in a post for IFL Science:

"This pattern of pronoun use suggests people with depression are more focused on themselves, and less connected with others. Researchers have reported that pronouns are actually more reliable in identifying depression than negative emotion words."

What remains unclear, though, is whether people who are more focused on themselves tend to depression, or if depression turns a person's focus on themselves. Perhaps unsurprisingly, people with depression also use more negative descriptors, like "lonely" and "miserable."

But, Al-Mosaiwi notes, it's hardly the most important clue when using language to assess clinical depression. Far better indicators, he says, are the presence of "absolutist words" in a person's speech or writing, such as "always," "constantly," and "completely." When overused, they tend to indicate that someone has a "black-and-white view of the world," Al-Mosaiwi says. An analysis of posts on different internet forums found that absolutist words were 50 percent more prevalent on anxiety and depression forums, and 80 percent more prevalent on suicidal ideation forums.

Researchers hope these types of classifications, supported by computerized methods, will prove more and more beneficial in a clinical setting.

[h/t IFL Science]

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