PITTSBURGH – The most extensive study ever of concussions in college and high school athletes may soon yield the answers to several perplexing questions coaches and trainers have been asking for decades.

Namely, when is it safe for a player with a concussion to resume playing? And how many concussions are too many, and should cause an athlete to retire?

The $3 million, five-year study by researchers and doctors at the University of Pittsburgh and Carnegie Mellon University, funded by a grant from the National Institutes of Health, is designed to objectively study the effects of single and multiple concussions on athletes’ brains.

By the end of the study, researchers hope to draw up a definitive timetable of how long an athlete should wait before playing following a concussion. The determination is critical because an athlete suffering a second concussion while still recovering from an earlier one risks permanent brain injury or death.

A concussion occurs when a person’s brain is violently rocked back and forth due to a blow to the head or the upper body. Concussions disturb brain activity and can cause brain swelling, blood vessel damage and even death; 17 athletes are known to have died between 1992 and 1997 following a second concussion.

“Whether or not an athlete should keep playing has always been based on opinion, not on science,” said Mark Lovell, a neuropsychologist and the director of the UPMC Center for Sports Medicine concussion program. “But this could be is the missing link.”

The findings will be used in professional sports, too. Lovell is the director of neuropsychological testing for the NFL and NHL and is the director of concussion testing for CART and the Indy Racing League.

Lovell is among 25 experts making presentations at a weekend seminar in Pittsburgh on concussions. Those attending will be told that of the estimated 600,000-plus high school and college athletes in the United States, an estimated 10 percent – or about 60,000, 63 percent of them in football – have concussions each year.

Because traditional testing means such as CT scans, MRIs and neurological exams often fail to detect concussions, thousands of athletes with concussions may never know it.

Some findings to be presented this weekend are based on data gathered through computerized tests developed by Lowell and colleagues and administered each year at more than 250 high schools and 70 colleges and pro sports teams.

“We’ve learned more about concussions in the last three years then we learned in the previous 30 years,” said Hermon native Dr. Michael Collins, a neuropsychologist and an instructor at Pitt’s department of orthopedic surgery.

As an example, researchers now believe that amnesia, not unconsciousness, is the most telling warning sign of a concussion, perhaps as much as 10 times so.

Also, while the sports most often played by girls and women, such as basketball, soccer and softball, usually aren’t considered as violent or dangerous as football, wrestling or hockey, females appear to sustain concussions at a higher rate than males.

Because of that, the UPMC Center for Sports Medicine is distributing hundreds of foldable plastic pocket cards to athletic trainers. The cards list 14 questions that should be asked immediately of an athlete who has just sustained a possible concussion.

Among the questions are: What stadium is this? Who is the opposing team? What was the score of the game before the hit?

The athlete is also asked to repeat the words girl, dog and green in order and to say the numbers 63 and 419 backward. If the athlete cannot answer any of the questions, the trainer is advised to immediately consult a physician.

During the study, researchers also want to learn if there are significant differences in the concussions sustained by high school and college athletes. High school athletes are seen as being more at risk because they don’t always have doctors and qualified trainers on site at their games.

“We’re finally finding ways to manage this injury,” Collins said. “But we’ve still got a lot to learn about this injury.”