Researchers Look for Link Between Brain Injury, Psychiatric Illness

Traumatic brain injury, the hallmark wound of the war in Iraq, may cause a number of neurological and psychiatric disorders, but more prospective research is needed to understand its long-term effects, a committee of the Institute of Medicine (IOM) reported in December 2008.

“There is a paucity of information in the scientific literature regarding the sequelae of blast injury, and there is a need for prospective, longitudinal studies to confirm reports of long-term effects of exposure to blasts,” said the report, commissioned by the Department of Veterans Affairs and based on an analysis of 1,900 peer-reviewed studies.

“There has been little information on the psychiatric history or psychological testing of troops before they are deployed,” said committee member Carol Tamminga, M.D., a professor of psychiatry and chief of translational research in schizophrenia at the University of Texas Southwestern Medical Center in Dallas, in an interview with Psychiatric News. “We would like to see more information gathered from soldiers in advance to establish a baseline and see if we can determine who is susceptible.”

The study covered penetrating traumatic brain injuries (TBIs)—those caused by, say, bullets or shrapnel—and closed-head injuries—those caused by the concussive force of a blast or explosion. The former were more common in previous wars, while the latter are more characteristic of injuries sustained by troops attacked with roadside bombs in Iraq and Afghanistan. Studies reviewed by the committee also included those documenting the effects of injuries caused by motor vehicle accidents and other nonmilitary events.

The IOM committee, chaired by George Rutherford, M.D., a professor of epidemiology and biostatistics at the University of California, San Francisco School of Medicine, found sufficient evidence that penetrating TBIs could cause unprovoked seizures and an average five-year decrease in lifespan. Severe or moderate closed TBIs could also produce unprovoked seizures in victims.

The IOM also found “sufficient evidence of an association” for several other neurological problems in severe or moderate cases of closed TBI and the same level of evidence for depression, aggression, and postconcussion symptoms (headache, dizziness, and memory problems) among severe, moderate, and even mild cases of TBI.

“The causes are quite complex,” said Tamminga. “Not every TBI has psychiatric consequences, so the context and nature of individual studies is critical.”

The IOM looked at four primary and five secondary studies associating TBI with mood disorders and found that post-TBI depression was not entirely explained by previous diagnosis of the disorder, but that rates were higher among patients with prior depression. The report found no evidence associating TBI with mania or bipolar disorder. There was limited evidence connecting it to completed suicide, and inadequate evidence for a link to attempted suicide. There was also sufficient evidence for an association between TBI and aggressive behavior, primarily when there was frontal-lobe damage. Severe, but not mild, TBI was associated with poorer social functioning and later unemployment.

The incidence of posttraumatic stress disorder (PTSD) varied in opposite ways for civilian and military patients, said Rutherford, at a news conference in Washington, D.C.

“For civilians, TBI was protective against PTSD, apparently because amnesia extinguishes memory of the event,” he said. “But among military personnel, repeated exposure to traumatic events surrounding a bomb blast increases PTSD risk.”

PTSD and depression most commonly occur within a year after a TBI occurs, but limited evidence suggests that cases of psychosis, while rare, become evident only two or three years following the incident, said Tamminga. That delay in onset can present problems in establishing the etiology of any post-TBI psychosis.

Recall bias engendered by self-reports of blast incidents, and outcomes appearing months or years after the event detracted from the strength of many studies, in the eyes of IOM reviewers.

“Soldiers don't report TBI because they don't want to complain and want to stay with their units,” said Tamminga. “We can't always be sure if they've had one TBI, and if they have a second, it potentiates the effects [on psychiatric outcomes].”

More long- and short-term data are needed to fill the gaps identified in the report. For one thing, everyone exposed to a blast should be evaluated by a medic or corpsman as soon as possible using the Brief Traumatic Brain Injury Screen and the Military Acute Concussion Evaluation, the IOM committee recommended.

“We need better accounting of mild brain injuries as they occur,” said Rutherford. “The idea is the closer to the event you record the information, the more accurate it will be.”

The Department of Defense and the Department of Veterans Affairs (VA) should also support longitudinal studies of TBI and associated trauma in humans and experimental studies using animal models. The VA should also create a registry of veterans with TBI and develop comparison groups to allow valid controls in future studies, said the report.

Soldiers with a TBI should be compared with injured people without TBI or blast exposure, with uninjured deployed veterans, and with uninjured nondeployed troops who have served on active duty, said the report.

“The worst kinds of studies are those that compare TBI [military] patients with the general population” because the context of the events is so different, said Rutherford.

Information on “Gulf War and Health: Volume 7: Long-Term Consequences of Traumatic Brain Injury” is posted at<www.nap.edu/catalog.php?record_id=12436>.▪