More than half of US Facebook members have taken breaks from the leading social network, with the top reason being they are just too busy, according to a study released Tuesday.

About 61 percent of US users said they had taken time off from Facebook at some point, with 27 percent planning to spend less time on it in the coming year, the Pew Research Center said.

The largest group -- 21 percent -- said they had taken a break because they were too busy. Other reasons included being "tired of stupid comments," "crazy" friends, boredom, and having it cause love life problems.

"These data show that people are trying to make new calibrations in their life to accommodate new social tools," said Pew Internet Project director Lee Rainie, a co-author of the study titled "Coming and Going on Facebook."

"They are adding up the pluses and minuses on a kind of networking balance sheet and they are trying to figure out how much they get out of connectivity vs. how much they put into it."

Slightly more than two-thirds of adults in the United States who use the Internet belong to Facebook, according to Pew.

A fifth of those who were not Facebook members said they once belonged to the service but quit, the study said.

Reasons given for leaving included getting tired of "minding everybody else's business" and it "takes my time away."

The survey, which has a margin of error of plus or minus 3.6 percentage points, was based on telephone interviews between December 13 and 16 with 1,006 adults living in the continental United States.