the Pentagon said in a memo released on Friday.

Deputy Defense Secretary Kathleen Hicks also said the armed forces should work to reduce exposure by increasing the distance between service members and weapon blasts during training exercises. She added that all personnel involved in high intensity training that could include explosions or the firing of weapons should be wearing protective gear.

“Blast overpressure is one of many factors that can negatively affect warfighter brain health,” Hicks wrote in the statement, which said her directive “builds on existing efforts” across the services to “mitigate the impacts of blast overpressure.”

Hicks’ directive comes nine months after U.S. Army Reserve soldier Robert Card shot and killed 18 people at a bar and bowling Alley in Lewiston, ME and injured 13 others. An autopsy disclosed that he had an undiagnosed traumatic brain injury which could have been responsible for the incident.

Card had been an instructor in hand grenade training and is thought to have been exposed to potentially thousands of low level blasts over the course of his career, which could have had a traumatic impact on his brain.

Hicks said in her memo that blast overexposure’s effects on the brain are not yet fully understood, but researchers have concluded that repeated blasts, even at low levels, can have negative consequences on cognitive performance and show and other negative impacts on the human brain, which can show up in the form of headaches, trouble paying attending and memory loss.

The U.S. Army put a brain testing rule in place in effect in June. Lt. Col. Randy Ready, spokesman for the Army’s Center for Initial Military Training, told Army Times the service will use the Automated Neuropsychological Assessment Metrics tool.

“All new soldiers going through basic training or One Unit Station Training will take the ANAM,” Ready wrote to Army Times.

Hicks’ directive applies to all branches of the armed services.