Among military veterans who die by suicide, those who experience a traumatic brain injury (TBI) during service take their lives 21% sooner after deployment than those without a TBI history, a new study shows.
Investigators also found that increases in new mental health diagnoses are significantly higher in soldiers with a history of TBI — in some cases, strikingly higher. For example, cases of substance use disorder rose by 100% among veterans with TBI compared to just 14.5% in those with no brain injury.
"We had had pieces of these findings for a long time but to be able to lay out this longitudinal story over time is the part that's new and important to really switch the focus to people's whole lives and things that happen over time, both psychological and physical," lead author Lisa Brenner, PhD, director of the Veterans Health Administration (VHA) Rocky Mountain Mental Illness Research Education and Clinical Center, Aurora, Colorado, told Medscape Medical News.
"If we take that life-course view, it's a very different way about thinking about conceptualizing exposures and conceptualizing risk and it's a different way of thinking about treatment and prevention," added Brenner, who also is a professor of physical medicine and rehabilitation, psychiatry, and neurology at the University of Colorado Anschutz School of Medicine. "I think that definitely applies to civilian populations."
The findings were published online July 31 in JAMA Network Open.
Largest, Longest Study To-Date
Researchers have long suspected that TBI and a higher rate of new mental illness and a shorter time to suicide are all somehow linked. But this study examined all three components longitudinally, in what is thought to be the largest and longest study on the topic to-date, including more than 860,000 people who were followed for up to a decade.
Investigators studied health data from the Substance Use and Psychological Injury Combat Study database on 860,892 US Army soldiers who returned from deployment in Iraq or Afghanistan between 2008 and 2014 and were 18-24 years old at the end of that deployment. They then examined new mental health diagnoses and suicide trends over time.
Nearly 109,000 (12.6%) experienced a TBI during deployment, and 2695 had died by suicide through the end of 2018.
New-onset diagnoses of anxiety, mood disorders, posttraumatic stress disorder, alcohol use, and substance use disorder (SUD) after deployment were all more common in soldiers who experienced PTSD while serving compared with those with no history of TBI.
There was a 67.7% increase in mood disorders in participants with TBI compared to a 37.5% increase in those without TBI. The increase in new cases of alcohol use disorder was also greater in the TBI group (a 31.9% increase vs a 10.3% increase).
But the sharpest difference was the increase in substance use disorder among those with TBI, which rose 100% compared to a 14.5% increase in solders with no history of TBI.
Sharp Differences in Time to Suicide
Death by suicide was only slightly more common in those with TBI compared to those without (0.4% vs 0.3%, respectively). But those with a brain injury committed suicide 21.3% sooner than those without a head injury, after the researchers controlled for sex, age, race, ethnicity, and fiscal year of return from deployment.
Time to suicide was faster in those with a TBI and two or more new mental health diagnoses and fastest among those with TBI and a new SUD diagnosis, who took their own lives 62.8% faster than those without a TBI.
The findings offer an important message to medical professionals in many different specialties, Brenner said.
"Folks in mental health probably have a lot of patients who have brain injury in their practice, and they don't know it and that's an important thing to know," she said, adding that "neurologists should screen for depression and other mental health conditions and make sure those people have evidence-based treatments for those mental health conditions while they're addressing the TBI-related symptoms."
Applicable to Civilians?
"The complex interplay between TBI, its potential effects on mental health, and risk of suicide remains a vexing focus of ongoing investigations and academic inquiry," Ross Zafonte, DO, president of Spaulding Rehabilitation Hospital Network and professor and chair of Physical Medicine and Rehabilitation at Harvard Medical School, Boston, and colleagues write in an accompanying editorial.
The study builds on earlier work, they added, and praised the study's longitudinal design and large cohort as key to the findings. The data on increased rates of new-onset substance use disorder, which was also associated with a faster time to suicide in the TBI group, was of particular interest.
"In this work, Brenner and colleagues identified substance use disorder as a key factor in faster time to suicide for active-duty service members with a history of TBI compared with those without TBI and theorized that a multiple stress or exposure burden may enhance risk," they write. "This theory is reasonable and has been postulated among individuals with medical sequelae linked to TBI."
However, the authors caution against applying these findings in military veterans to civilians.
"While this work is critical in the military population, caution should be given to avoid direct generalization to other populations, such as athletes, for whom the linkage to suicidal ideation is less understood," they write.
The study was funded by National Institute of Mental Health and Office of the Director at National Institutes of Health. Brenner has received personal fees from Wolters Kluwer, Rand Corporation, American Psychological Association, and Oxford University Press and serves as a consultant to sports leagues via her university affiliation.
Zafonte reported receiving royalties from Springer/Demos; serving as a member of the editorial boards of Journal of Neurotrauma and Frontiers in Neurology and scientific advisory boards of Myomo, Nanodiagnostics, Onecare.ai, and Kisbee; and evaluating patients in the MGH Brain and Body-TRUST Program, which is funded by the National Football League Players Association. Full disclosures for all authors can be found in the original articles.
Kelli Whitlock Burton is a reporter for Medscape Medical News covering psychiatry and neurology.