NEW YORK — As our social lives have moved onto social media sites like Facebook over the past decade, there’s been a lot of hand-wringing over what all that screen time might be doing to our health.

But according to a new paper, time spent on social media could be associated with a longer life.

The paper, published Monday in the journal PNAS, asserts that the health effects of active online social lives largely mirror the benefits of busy offline social lives.

“We find that people with more friends online are less likely to die than their disconnected counterparts,’’ the paper says. “This evidence contradicts assertions that social media have had a net-negative impact on health.’’

The study’s methods are detailed at length in the paper, and it was approved by three university and state review boards. But skeptics will note that Facebook itself was closely involved with the paper. William Hobbs, 29, a postdoctoral fellow at Northeastern University, worked at Facebook as a research intern in 2013. Another of the paper’s authors, Moira Burke, worked on it in her capacity as a research scientist at Facebook.

Hobbs, who conducted the research while he was a doctoral student at the University of California, San Diego, said Facebook had not interfered with the results of the paper.

“We had some things in writing that they couldn’t interfere with the publication of the research no matter what the result was,’’ he said. He noted, though, that some at the company had been “pretty confident that we were going to find this result.’’

A news release sent by a spokeswoman at the University of California, San Diego, drives the point home. “The research confirms what scientists have known for a long time about the offline world: People who have stronger social networks live longer,’’ the release said.

The study was based on 12 million social media profiles made available to the researchers by Facebook, as well as records from the California Department of Health.

It found that “moderate use’’ of Facebook was associated with the lowest mortality rate, and that receiving friend requests correlated with reduced mortality, but that sending friend requests did not.

Hobbs and the paper’s other authors matched records from California’s Department of Public Health with those of California Facebook users, preserving privacy by aggregating the data before analyzing it, the release said. All the subjects of the study were born from 1945 to 1989.

The paper found that people with large or even average social networks lived longer than people who had very small social networks. It was “a finding consistent with classic studies of offline relationships and longevity,’’ the release said.

The paper itself acknowledges the study’s “many limitations,’’ saying that Facebook is unique among social media websites and that its data might not be more broadly applicable. It also points out that its findings represent a correlative relationship as opposed to a causal one: There is no evidence in the paper that using Facebook has any direct effect on a person’s health.

James Fowler, a professor of public health and political science at the University of California, San Diego, and another of the paper’s authors, said he had been surprised that requesting the friendship of others was not found to be associated with a longer life span.

“I had hoped we would find that reaching out to others was associated with better health,’’ he said.

The new result, Fowler explained, suggested that researchers who had previously found that people with more friends were healthier might have misunderstood the relationship between sociability and health. It may be, he said, that “the reason why people with more friends are healthier is because healthier people have more friends,’’ which would suggest that “it may be harder than we thought it was to use social networks to make people healthier.’’

Sociological research into Facebook’s effect on health and happiness has not always been as positive. A study published in the journal PLOS One three years ago found that over a two-week period, the more its subjects used Facebook in a certain time span, the worse they rated their own happiness within that time span.