Experts have further suggested widespread anxiety and depression, environmental hormone disrupters, and concerns over sexual misconduct in the wake of the #MeToo movement as possible factors in the decline in sexual activity.
The General Social Survey also found a significant gender disparity in results reported by young people. In 2008, the numbers of men and women ages 18-30 who had gone a year without sex both hovered around 10%. In 2018, 18% of women in this age group said they had not had sex in the past year, compared to 28% of men.
In her comments to the Washington Post, Twenge noted that more young men than women are living with their parents.
Pornography could also be playing a role. Pornhub, the most-visited pornography site in the U.S., has seen its daily visits triple from 2012 to 2017.
In a series of studies examining pornography use, "The Social Costs of Pornography: A Collection of Papers" published by the Witherspoon Institute, researchers found that those who viewed pornography became less satisfied with their sex lives, and that viewing porn just once can lead to feelings of dissatisfaction toward a human partner.
According to a 2012 article in Psychology Today by clinical psychologist Tyger Latham, Psy.D, erectile dysfunction, once considered an issue plaguing old men, is arising more in young men who rely heavily on pornography to become sexually aroused. A study by the Italian Society of Andrology and Sexual Medicine surveyed 28,000 men on their internet porn habits, and found that porn use over time led to a lower sex drive and an eventual inability to become aroused at all.
Pornography could also be contributing to the continuing decline in marriage rates.
Mark Regnerus, an associate professor of sociology at the University of Texas at Austin and a Catholic who has studied religion and sexual behavior, cautioned against assuming that correlation equals causation – but said that pornography use is likely part of a more complex reason for dropping marriage rates.
"We know that both things are occurring, but it's difficult to establish a causal connection," he told CNA in a 2015 e-mail interview. "A variety of things are contributing to the declining marriage rate."
"I don't think porn use necessarily causes that, but contributes to it (together with diminished earnings power, diminished confidence, etc.)," he added. "To be sure, porn use doesn't help build confidence in men, something that's pretty necessary (but not sufficient) to be considered marriageable. So I'd say porn use is a suspect here, but connecting the dots is hardly straightforward."
In a new comments to CNA this week, Regnerus pointed to "the flight from marriage" and satisfaction derived from both social media and pornography as major factors driving the decline in sex.
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This situation is aggravated, he said, by "the increasing 'similarity' of men and women in the modern marketplace…We're settling for something less than the age-old pursuit of wooing, or being wooed by, our spouse."
"I doubt that a surge in human happiness is ahead," he commented.