College football players reported having six suspected concussions for every one diagnosed concussion, according to a recent study of 730 Football Championship Subdivision players.

Convincing players to honestly report concussion symptoms vary by the position of a player -- offensive linemen tend to stay quiet the most -- and can be impacted by a coach’s own beliefs about reporting concussions. Those were among the findings in recently-published studies by the Boston University CTE Center and Harvard University.

The survey led by researcher Christine Baugh found that players indicated that for every one concussion diagnosed, there were another 21 “dings” or “bell-ringers,” meaning less than 4 percent of possible concussions were reported. Not all of these additional head impacts necessarily resulted in concussions, yet they went unreported among a cohort of players who participate in Division I's lower classification of college football.

By their very nature, athletes are competitive and want to keep playing even when they sustain concussion-like symptoms. The country saw that Saturday when woozy Michigan quarterback Shane Morris waved off coming to the sideline after a hit to the head. Michigan, which said Morris was diagnosed with a concussion Sunday, has apologized for allowing him to continue to play.

Michigan coach Brady Hoke said medical professionals, not coaches, decide if an injured player stays in the game. Michigan athletic director Dave Brandon told The Detroit Free Press on Thursday that Hoke had no fault in the handling of Morris' brain injury and placed the blame on the school's medical staff.

Some people in the concussion community, though, cringed at Hoke’s statement Saturday when he said, “I don't know if he had a concussion or not, I don't know that. Shane's a pretty competitive, tough kid. And Shane wanted to be the quarterback, and so, believe me, if he didn't want to be he would've come to the sideline or stayed down.”

One study by Baugh of the FCS players found that coaches’ behavior -- or at least players’ perceptions of their coaches’ attitudes -- may play a significant role in whether players report symptoms.

The researchers asked players to what extent they agreed with the statement, “If I report what I think might be a concussion my coach will think I did the right thing.” Freshmen had the strongest level of agreement, then sophomores, then juniors, and least of all seniors. The biggest drop was between the freshman and sophomore years.

The authors noted the perception difference of coaches could be due to freshmen getting more exposure to concussion education in high school than their older college teammates. But the study said it’s “troubling” that non-freshmen players see their coach as less supportive of concussion reporting than freshmen players.

Researchers found that perceived coach support for concussion reporting was significantly related to the number of times players played through concussion symptoms. Players who thought their coach was less supportive of concussion reporting also indicated significantly more undiagnosed concussions than peers who received greater coach support.

Running backs indicated they sustained the most undiagnosed concussions, followed by offensive linemen. Although offensive linemen had concussions diagnosed at a similar rate as other positions, they indicated sustaining 62 percent more suspected concussions and 52 percent more “dings” or “bell ringers.”

The researchers wrote that although conferences and the NCAA have guideline restrictions for full-contact practices, the changes may not benefit offensive linemen as much as other positions. The study wrote that the findings suggest offensive linemen, who experience frequent but low-magnitude head impacts, develop more post-impact symptoms than any other position but don't report them as a concussion.

“Given the known difference in impacts experienced across playing positions, it is possible that athletes experiencing more frequent impacts begin to consider them a routine or normative aspect of their positional role and feel less compelled to report symptoms that may result,” the study said.

Baugh’s team discovered gaps in how the NCAA educates players about concussions. The NCAA requires that schools receive written acknowledgements from players that they have received concussion education and understand their responsibility to report symptoms to the medical staff. These acknowledgments are in part for liability purposes.

Eight of the 10 FCS schools in the study required that athletes acknowledge receiving this information. Approximately 40 percent of the athletes who athletic trainers said provided acknowledgment did not recall having done so, the study said.

Many athletic trainers of schools in the study said athletes may be getting bombarded with so much concussion information that retention is low. Also, the study found some schools provided the education materials on the same form that players had to sign and return to the school. 

“By complying with one facet of the NCAA concussion policy (acknowledgment of information receipt), some institutions may be partially compromising the educational facet of the mandate,” the study said.

The surveys were conducted in 2013 with 10 FCS football teams whose coach or athletic trainer expressed interest in participating. Five teams came from the Midwest, four from the Northeast and one from the South.