Writers are often among a society’s boldest, most fearless voices—the ones most willing to make statements that challenge the status quo.

But that could be changing, according to a report by PEN American Center, the largest branch of the literary and human rights group PEN International. In a new survey of 772 writers living in 50 countries, the organization found that 34 percent of writers in free nations and 61 percent in authoritarian ones either avoided speaking up about a topic or seriously considered staying quiet because they were concerned about government surveillance—particularly after the National Security Agency’s PRISM program was exposed by Edward Snowden in 2013.

The results, reported in “Global Chilling: The Impact of Mass Surveillance on International Writers,” are more pronounced in social media: 42 percent of writers in free countries and 53 percent in not-free ones have reduced their participation in social media or eliminated it or have seriously considered doing so. And 31 percent of writers in free countries and 68 percent in not-free nations have self-censored in phone and email communications.

The finding that self-censorship is occurring even in free societies was of particular concern to PEN American Center.

“The levels of self-censorship reported by writers living in liberal democracies are astonishing and demonstrate that mass surveillance programs conducted by democracies are chilling freedom of expression among writers,” the report states. “Awareness of mass surveillance in democratic societies is prompting many writers to behave similarly to those living in countries with histories of widespread state surveillance, indicating that these writers are not confident that their governments will not abuse the information collected under these surveillance programs.”

The reach of the NSA programs has raised significant concerns in numerous sectors of the business world, such as cloud computing. But writers often feel the pressure before others do, PEN officials say.

“Writers are the ones who experience encroachments on freedom of expression most acutely, or first,” PEN American Center Executive Director Suzanne Nossel said in comments to The New York Times. “The idea that we are seeing some similar patterns in free countries to those we’ve traditionally associated with unfree countries is pretty distressing.”

PEN America, which has 3,700 members worldwide, is calling on Congress to pass reforms to federal surveillance programs.

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