The number of former servicemembers enrolled in the Department of Veterans Affairs system who have had traumatic brain injuries spiked considerably in the last four years on record, new data from the department shows.

The figures, which were posted on the VA website last week, demonstrate that the number of reported TBI instances in the VA’s database grew by 26% between 2021 and 2025 — and experts believe this figure understates the total.

The new statistics come in the wake of Congress appropriating 77% less for Defense Department medical research into TBI and psychological health between fiscal 2024 and fiscal 2026.

The VA data shows that over the two decades following the 9/11 attacks — from 2001 to 2021 — 441,639 veterans either screened positive for a TBI, received a TBI-related diagnosis in VA medical records or filed claims for VA disability compensation.

In just the last four years, the number of cases since 2001 grew to 556,502 people, a 26% increase that represents an average of more than 28,000 additional cases per year since 2021, the report indicates.

At the same time, Congress has reduced the amount of funding put toward the Pentagon-funded program to research detection and treatment of TBIs and to understand psychological health issues, including those that can come with TBIs, such as post-traumatic stress disorder.

Spending on this initiative has dropped from $175 million in fiscal 2024 to $40.5 million in fiscal 2026, and the House’s Defense spending bill for fiscal 2027 would not increase the funding. The House Appropriations Committee approved that bill on June 24.

Despite the recent cuts, Pentagon-funded research on TBI and other diseases has strong supporters in Congress, ranging from Sen. Susan Collins, R-Maine, chair of the Senate Appropriations Committee, to Rep. Rosa DeLauro of Connecticut, the top Democrat on the House Appropriations Committee.

“The uptick in reported TBI cases among veterans underlines the urgency to increase funding for the Congressionally Directed Medical Research Program to study servicemembers’ and veterans’ brain injuries,” Rep. Mike Levin, D-Calif., a member of the Appropriations Committee who has been a consistent supporter of the Pentagon’s medical research program, said in an email.

“While the recently passed defense funding bill in the House Appropriations Committee maintains the 2026 funding level for TBI research at $40.5 million, this is a drastic cut from prior years,” Levin added. “We need a substantial increase in research funding to determine the appropriate care and resources for our troops and veterans, and I will continue to fight for that on the House Appropriations Committee.”

The total number of cases only covers veterans who have engaged with the VA system and excludes undiagnosed cases and instances where a TBI was misdiagnosed as post-traumatic stress disorder or another issue, according to a statement Monday from Disabled American Veterans National Commander Coleman Nee and Invisible Wounds Foundation CEO Shannon Connell.

The higher numbers may also be due at least in part to greater reporting and screening, Nee and Connell said.

Regardless, they said, the new statistics underscore the importance of funding research to find diagnostic tools and treatments for TBI.

“Traumatic brain injuries are one of the most prominent wounds suffered in modern warfare, and the number of veterans reflected in the VA data underscores the scale of this issue,” Nee and Connell said. “Congress must act now to drive research to prevent, diagnose and treat TBI in the military and veteran communities.”

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