A survey of writers around the world by the PEN American Center has found that a significant majority said they were deeply concerned with government surveillance, with many reporting that they have avoided, or have considered avoiding, controversial topics in their work or in personal communications as a result.

The findings show that writers consider freedom of expression to be under significant threat around the world in democratic and nondemocratic countries. Some 75 percent of respondents in countries classified as “free,” 84 percent in “partly free” countries, and 80 percent in countries that were “not free” said that they were “very” or “somewhat” worried about government surveillance in their countries.

The survey, which will be released Monday, was conducted anonymously online in fall 2014 and yielded 772 responses from fiction and nonfiction writers and related professionals, including translators and editors, in 50 countries.

Smaller numbers said they avoided or considered avoiding writing or speaking on certain subjects, with 34 percent in countries classified as free, 44 percent in partly free countries and 61 percent in not free countries reporting self-censorship. Respondents in similar percentages reported curtailing social media activity, or said they were considering it, because of surveillance.