Americans are having less sex.

Should we care? Does it matter?

Experts who talked to Healthline say it does — from the ability to have a relationship to maintaining good mental health.

A recent study in Archives of Sexual Behavior found that people in the United States who were living together or married had sex less often between 2010 and 2014 compared with those who were together from 2000 to 2004.

This includes millennials, too.

Dr. Jean M. Twenge, the 2017 study's lead author, and professor of psychology at San Diego State University, conducted research last year that found millennials had fewer sexual partners than Gen Xers. She is the author of “Generation Me: Why Today's Young Americans Are More Confident, Assertive, Entitled — and More Miserable Than Ever Before.”

“Despite their reputation for hooking up, millennials and the generation after them (known as iGen or Generation Z) are actually having sex less often than their parents and grandparents did when they were young,” Twenge said in a statement. “That's partially because fewer iGeners and millennials have steady partners.”

Read more: Millennials having less sex than Generation X »

Understanding millennials and sex

Her 2016 research found that 15 percent of 20- to 24-year-olds born in the 1990s had not had any sexual partners since age 18, compared to only 6 percent of Gen Xers when they were young adults.

Twenge says the numbers aren’t indicative of the stereotype of the generation that they have a lot of sex with multiple partners.

“Online dating apps should, in theory, help millennials find sexual partners more easily,” Twenge said in a statement. “However, technology may have the opposite effect if young people are spending so much time online that they interact less in person, and thus don’t have sex.”

Dr. Jenni Skyler, a certified sex therapist, sexologist, and a licensed marriage and family therapist with The Intimacy Institute in Colorado, said that electronic distractions are one reason why young people may have sex less.

There are also other barriers.

“People lay in bed on their tablets or phones, isolated from one another in an electronic medium that can be almost addictive. At least when people were lying in bed before with just the TV as a barrier, they could cuddle and watch the same show, upping the odds for sensual contact,” she told Healthline.

Dr. Tammy Nelson, a certified sex therapist and licensed couples’ counselor, who wroteThe New Monogamy,” told Healthlinethat technology may play a factor in how millennials approach sex.

They may depend on pornography, social media, or cyber relationships for instant gratification and uncomplicated relationships.

“Perhaps cyber relationships and even sex with themselves or virtual partners is easier, faster, and less complicated than with their real life committed partner or spouse,” Nelson explained.

If that is the case, it doesn’t necessarily mean that they are any less happy than other generations, she added.

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The ramifications of less sex

In her 2016 study, Twenge noted that 45 percent of millennials had slept with someone other than a partner or spouse when they were in their late teens or 20s. That’s up from 35 percent of Gen Xers at the same age.

“It's hard to say if millennials’ rate of sexual frequency will increase once they get into relationships,” she said.

People getting married at age 30 may have less sex than if they’d married at 22 like baby boomers did.

“Millennials are more likely to spend their years of peak sexual frequency without a steady partner, which might cut down on their total lifetime sexual frequency,” Twenge said.

While they may be having sex less often, more of them are sleeping with people they are not “in a relationship” with.

Does it put millennials more at risk for sexual health complications?

A 2016 CDC report noted a rise in sexually transmitted infections (STIs) such as chlamydia (up 6 percent since 2014), syphilis (up 19 percent), and gonorrhea (up nearly 13 percent).

Nearly 20 million new STI cases happen each year, the CDC says, and more than half of those are in people ages 15 to 24.

Some experts say that social media and technology has fueled this phenomenon.

Dr. Ryne Sherman, an associate professor at Florida Atlantic University who co-authored the 2016 study, said sexual frequency is tied to mental and physical health, though it is tough to confirm that more sex causes greater health, or if greater health causes more sex.

He suspects that it goes both ways.

“Our results are very consistent with the view that mental health is a real problem for millennials [compared with previous generations],” Sherman told Healthline.

Dr. Fran Walfish, a family and relationship psychotherapist based in California, said the less-sex trend could be problematic for marriages — assuming that millennials still have less sex if they do marry. She noted a trend of young people in their 20s and 40s are in sexless marriages.

“Lack of sex has many causes, including ‘we just had a baby,’ to being worn out by the kids, financial strain, or career demands. No matter the cause, at the root is a common denominator. Lack of communication,” Walfish told Healthline. “And, when marital communication breaks down, sex falls apart. Divorce often ensues.”

Millennials also aren’t as focused on marriage and children, and aren’t taking these steps as did the generations before them, she added.

Those that do marry and try to have kids later on could face age-related pregnancy risks and infertility issues.

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Safer sex?

Twenge has said that millennials are “very interested in safety, which also appears in their reduced use of alcohol and their interest in ‘safe spaces’ on campus.”

“This is a very risk-averse generation, and that attitude may be influencing their sexual choices,” Twenge noted.

Millennials do not have drastically fewer sex partners and drastically lower sexual frequency, just lower than other generations given their age and the time in which they live, Sherman added.

Millennials could be one of the safest generations when it comes to sex, he contended.

The CDC reports in its Youth Risk Behavior Survey, that 41 percent of high school students had engaged in sex in 2015, down from 54 percent in 1991.

“This generation appears to be waiting longer to have sex, with an increasing minority apparently waiting until their early 20s or later,” said Twenge. “It’s good news for sexual and emotional health if teens are waiting until they are ready. But if young adults forgo sex completely, they may be missing out on some of the advantages of an adult romantic relationship.”

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How much sex aren’t we having?

Americans also had sex about nine fewer times each year from 2010 through 2014 compared with 1995-1999, the 2017 report found.

Data was derived from the General Social Survey, which includes 26,000 adult participants who were asked about their sexual behaviors since 1989.

“These data show a major reversal from previous decades in terms of marriage and sex,” said Twenge in a statement.

“It is true, older and married people do, in fact, have sex less often. This may or may not correlate to age, being tired, or boredom with a long-term partnership,” Nelson said. “But for the ‘older’ people today, sexual frequency declines, but sex also improves as we age.”

“We get better in bed as we get older,” Nelson added. “We don’t measure sexual performance by the notches on our belts, but with the level of intimacy, the quality of eroticism, the variety, the fantasies we share with a partner, our capacity for helping our partner to orgasm, the loss of body image insecurities, and the delight and pleasure we find in the act of sex itself.”

Nelson encourages young people not to be dissuaded by the report.

“Sex is not going away. We are biologically created to seek pleasure, to be in partnerships of all kinds,” she explained.

People are living longer, healthier lives and can still enjoy sex later in life.

“Focus on sex, at any age, can bring intimacy and rewards for a lifetime,” she added.