U.S. soldiers who suffer a moderate or severe traumatic brain injury (TBI) are more likely to suffer other mental health woes than those with other serious injuries, a new study finds.

It also showed that the rate of mental health disorders among seriously injured soldiers is much higher than previously reported.

"A central takeaway is that severe TBI is associated with a greater risk of mental health conditions — not just PTSD [post-traumatic stress disorder]," said lead investigator David Chin, an assistant professor of health policy and management at University of Massachusetts Amherst.

Our findings suggest that patients who are critically injured in combat and sustain severe TBIs have particularly high rates of mental health disorders," Chin said in a university news release.

He and his colleagues analyzed the records of nearly 5,000 U.S. military members — mostly from the Army or Marines — who were severely injured during combat in Iraq and Afghanistan between 2002 and 2011. Nearly a third suffered moderate or severe TBIs.

Overall, 71% of the severely injured soldiers in the study were later diagnosed with at least one of five mental health conditions: post-traumatic stress disorder (PTSD), anxiety and mood disorders, adjustment reactions, schizophrenia and other psychotic disorders, and cognitive disorders.

While previous research concluded that far fewer (42%) seriously injured combat soldiers were later diagnosed with mental health disorders, Chin noted that this study defined mental health diagnoses more narrowly.

Diagnoses for all five mental health conditions were higher among soldiers with TBI than among those with other severe injuries, according to the findings.

The new study also found that the rate of PTSD is higher among soldiers with more severe TBI, not lower as reported in previous research.

"There was a common belief that having a severe TBI resulted in an amnestic effect on PTSD — the injuries were so severe that the patients have no memory of the event and that put them at lower risk of having mental health outcomes. This data showed to the contrary," Chin noted.

The findings were published recently in the journal Military Medicine.