A new study conducted by University of Gothenburg in Sweden shows that recovery from sports-related concussion takes longer time than previously believed, according to a statement published on Wednesday by the university.

"It has previously been believed that concussion heals in 7-10 days, and the Swedish Boxing Federation has decided the rest period to be of one month after a concussion, in order to be on the safe side," Sanna Neselius, researcher in the study, was quoted as saying in the statement.

"But our studies show that a concussion, such as may be experienced after being knocked out, can take more than four months to heal," said Neselius.

Neselius is a former boxer and member of the medical commission of the Swedish Boxing Federation, and her previous studies have shown that amateur boxing causes damage to nerve cells, that can take more than two weeks to heal.

In the new study, Neselius analyzed cerebrospinal fluid after concussion and the analysis can be used to determine the magnitude of brain injury and to follow its course.