LINCOLN, Neb. >> College coaches and administrators concerned about their tweeting athletes also should be wary of their tweeting fans.

Social media experts pointed to vitriolic messages directed at football players from Missouri and Nebraska last weekend as examples of why schools should counsel athletes on how to cope with criticism that crosses the line from heckling to hate.

“What I worry about is some of the psychological outcomes. Does it lead to decreased self-esteem? Does it lead to depression? Does it lead to guys not eating and sleeping right?” said Jimmy Sanderson, a Clemson researcher who collaborated on a 2012 study of how college athletes react to negative encounters with fans on social media.

College athletes have always been targets for criticism, whether through the mail, on radio shows or catcalls from the stands. Because of Twitter and other platforms, direct access to college and professional athletes has never been greater. Most interaction is positive. But the messages can get nasty when upset fans type words they surely wouldn’t say to an athlete’s face.

Last Saturday, after Missouri kicker Andrew Baggett missed a short field goal in overtime against South Carolina, he was accosted on Twitter. There were comments about his ability, homophobic slurs and one tweet that said “go kill yourself everyone in Missouri hates you.”

Baggett said this week that supportive tweets outnumbered the negative “20 fold.”

“Nobody’s comment made me feel worse than what I did on that field,” he said.

Nebraska’s Kenny Bell dropped a couple passes, including one in the end zone, during a loss to Minnesota. Like Baggett, Bell expressed appreciation for encouraging tweets, but he clearly was troubled by caustic ones. Especially disturbing was a tweet that played off the fact Bell’s dog had been hit by a car. That person later apologized on Twitter.

“Tonight was the first night that I have been truly bothered by the hateful comments by people,” Bell wrote in back-to-back tweets. “That being said…. It takes so much more effort to be mean an hateful than it is to be positive an supportive. I just don’t understand it.”

It would be unrealistic to cut off players from social media — though some coaches have tried — because online communication is ingrained in the culture and can be beneficial, Sanderson said. An athlete can use Twitter to build an online identity, which helps with networking, job searches and promoting the team and university.

Southern California last year began listing football players’ Twitter handles on online biographies and in weekly game previews available to fans and media.

“This is how people communicate today, especially those from the generation of our current student-athletes. Why not embrace it?” USC spokesman Tim Tessalone wrote in an email to The Associated Press. “It also helps our fans engage with our players and vice versa. Sure, there will be some mistakes, but that’s all part of the learning process for college kids.”

Tessalone said he’s not aware of any USC players having serious problems in interactions with fans.

Major athletic programs typically address social media with their athletes. Athletes generally are told to think twice before hitting the send button so they don’t put out something that embarrasses themselves, the team and the university. At Nebraska, athletes are urged to not lash out at people who criticize them, but there is no policy on what they should do if they are inundated with negativity.

“It might be something we need to get into based on things that have transpired,” said Keith Zimmer, Nebraska’s associate athletic director for life skills.

Kevin DeShazo, who provides social media training for athletes at about 50 schools for Oklahoma City-based Fieldhouse Media, said coaches and administrators need to be aware of online threats and harassment. He said law enforcement and the platform’s administrator should be notified in extreme cases. Illinois coach Tim Beckman requires his players to sign an agreement to notify coaches if they have problems.

DeShazo said denigrating messages should be ignored, even though the inclination would be to respond. “You can never win going back and forth with these people. They want you to do that,” he said.

Some athletes will retweet hateful messages so other fans can take on the source of outrageous comments. “It breeds compassion,” DeShazo said. “Fans will turn on that person.”

Of course, athletes can easily block people who are out of line from posting messages on their platforms.

Though the common perception of college football players is one of toughness, a steady stream of hate directed at a player after a bad game is akin to the cyberbullying that afflicts teenagers, Sanderson said.

Nebraska receiver Quincy Enunwa acknowledged he and his teammates can’t resist looking at their phones after games to see what fans are saying. If comments are too negative, Enunwa shuts his off for a while.

“When people are telling you things after a loss, you hear it so many times, you’re going to start to believe it,” Enunwa said.

Some players aren’t disciplined enough to put their phones down.

“Most kids that age, whether an athlete or not, are invested in what people are saying about them,” Sanderson said. “Love it or hate it, Twitter lets us know what people are saying about us, and when you see stuff like that, it can take a toll on you.”

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Associated Press freelance writer Jake Kreinberg in Columbia, Mo., and AP writer David Mercer in Champaign, Ill., contributed to this report.