Millennials are the least sexually active generation in decades. Study after study has shown that not only are millennials less likely to have had sex, but among those who are sexually active, they're doing it less often and with fewer partners.

Naturally, many of are curious about what's going on here—why aren't millennials getting it on more often? A common refrain is that porn is to blame. Intuitively, this explanation makes sense, right? I mean, there's no doubt that millennials have more access to porn than any previous generation. Now that porn can be accessed on demand for free 24/7, it only seems logical that it's starting to serve as a replacement for sex.

Unfortunately, there's one problem with this explanation: It's completely wrong. In a study published earlier this year in the Archives of Sexual Behavior, researchers analyzed a quarter century's worth of data from the General Social Survey, a nationally representative US survey conducted most years that inquires about Americans' sex lives, among other things. Since 1989, participants have been asked two key questions: whether they have seen a pornographic movie in the last year and how often they were having sex during the same time period. This allowed researchers to see whether these two things were related.

It turns out that Americans across the board—not just millennials—were having less sex today than they were in the past; however, millennials were doing it less than everyone else. And while this decline in sexual activity was linked to porn use, the results probably weren't what you were expecting. Specifically, rather than being linked to less sex, watching porn was actually linked to having more sex. In other words, though porn might seem like the logical target to blame when it comes to why millennials—and everyone else—are getting laid less often, it's not the right one.

So if it's not porn, then what else might be going on? Another common sense explanation is that it's due to changes in work-life balance. Working more should translate to a less active sex life. However, the new Archives study also discounts this possibility finding that, unexpectedly, working longer hours (like watching porn) was linked to more sex.

Instead, what we're seeing here likely has a lot to do with changing marriage patterns. Studies have pretty consistently found that married people tend to have more sex than single people; however, given that millennials are waiting longer and longer to get married (the average age of first marriage is now close to 30), perhaps that's part of the reason why they're less sexually active. In other words, if millennials are less likely to have a steady partner, that would help to explain why they're having less sex.

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There's more to the story than changes in marriage, though. Millennials are also more medicated than generations past, especially when it comes to anti-depressants. Young adults today are using these drugs at earlier ages and for far longer periods of time than ever before. It's well known that anti-depressants—especially Prozac and other selective serotonin reuptake inhibitors (SSRIs)—have sexual side effects. Notably, these drugs have a tendency to reduce sexual desire and inhibit sexual arousal.

On top of this, of course, there's also the role of technology, and I'm not talking about porn. More and more of our lives—both personal and professional—are taking place online. As we spend more time interacting virtually instead of in person, this necessarily creates fewer opportunities for sex. In other words, the more immersed we become in our phones and social media, the less likely it is that sex is going to happen spontaneously.

Also, to the extent that this reduced human contact makes us feel more lonely and depressed, this will only serve to compound the negative impact of technology on our sex lives by decreasing our libidos. Indeed, some have argued that this is why the post-millennial generation, or iGen as they're called, is even less sexually active than the millennials.

However, it's important to note that while technology might be partially responsible for the decline in sexual activity, technology is also creating new opportunities for sexual expression, such as through sexting and cybersex. So, when we're talking about millennials having less sex, we need to be mindful of the fact that what "counts" as sex is changing at the same time.