One in three men who played a contact sport in their youth had evidence of chronic traumatic encephalopathy (CET), according to a recent study by the Mayo Clinic.

The study, which was released Tuesday, links contact sports played in school, such as football, boxing, wrestling, rugby, basketball and baseball, with the development of CTE, which can affect mood, behavior and cognition.

A team of researchers examined the clinical records of 1,721 cases in the Mayo Clinic Brain Bank in Florida and found 66 men who had participated in contact sports during their youth and young adult years. Of those cases, 32 percent had CTE pathology, which only can be diagnosed posthumously.

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“The 32 percent of CTE we found in our brain bank is surprisingly high for the frequency of neurodegenerative pathology within the general population,” Kevin Bieniek, the study’s lead author, said in a press release. “If 1 in 3 individuals who participate in a contact sport goes on to develop CTE pathology, this could present a real challenge down the road.”

By comparison, none of the 198 brains of individuals who did not participate in contact sports, including 66 women, had CTE pathology, according to the study.

The Mayo Clinic published its full study in the December issue of Acta Neuropathologica.

“The purpose of our study is not to discourage children and adults from participating in sports because we believe the mental and physical health benefits are great,” Bieniek said. “It is vital that people use caution when it comes to protecting the head. Through CTE awareness, greater emphasis will be placed on making contact sports safer, with better protective equipment and fewer head-to-head contacts.”

Related: Contact Sports Don't Cause CTE, Study Says