No one has accused Facebook FB 1.37% of causing cancer, but Mark Zuckerberg now stands at a similar crossroads.

In the face of pressure brought by a growing roster of Facebook Inc. investors and former executives, many of whom have publicly stated that Facebook is both psychologically addictive and harmful to democracy, the Facebook founder and chief executive has pledged to “fix” Facebook, by doing a number of things including “making sure that time spent on Facebook is time well spent.”

Mr. Zuckerberg has also recently told investors he wants his company “to encourage meaningful social interactions,” adding that “time spent is not a goal by itself.”

Facebook researchers have acknowledged that while direct sharing between individuals and small groups on Facebook can have positive effects, merely scrolling through others’ updates makes people unhappy. PHOTO:ISTOCK

So here’s the multibillion-dollar question: Is Mr. Zuckerberg willing to sacrifice revenue for the well-being of Facebook’s two billion-plus users?

Mr. Zuckerberg has already said the company will hire so many content moderators to deal with fake news and Russian interference that it will hurt profits, but whether he will go further and change the basic fabric of Facebook’s algorithms in the name of users’ mental health, he has yet to say.

Clearly, Facebook, a company Mr. Zuckerberg started when he was in college, has changed so much that even its creator is playing catch-up to the reality of its globe-spanning power.

In June he changed the company’s mission from “connecting” the world to bringing the world closer together. He said he used to think giving people a voice would make the world better on its own, “but our society is still divided. Now I believe we have a responsibility to do even more.”

In December, Facebook researchers surveyed the scientific literature and their own workand publicly acknowledged that while direct communication and sharing between individuals and small groups on Facebook can have positive effects, merely lurking and scrolling through others’ broadcasted status updates makes people unhappy.

In a survey conducted in early 2017, the Royal Society for Public Health asked 1,500 young people to evaluate the five biggest social networks, to measure whether they are good or bad for mental health. The results showed all but one service had a negative effect on mental health. Facebook, Twitter , Snapchat and the Facebook-owned Instagram all pushed survey participants to contrast their lives with others, a phenomenon known as social comparison. The exception was YouTube, in part because the dynamic is usually one-to-many communication, with person-to-person socializing happening in comments.