WASHINGTON -- About 30 percent of traumatic brain injury patients will develop clinical depression, a level three times higher than the general population, according to a new study.

The results, which Vanderbilt University researchers derived from more than 100 previously published studies done over decades, are significant for the military because more than 200,000 U.S. servicemembers have been diagnosed with TBI since 2000. That translates to about 60,000 potential cases of depression as a result of brain injury for military members.

Depression is a mood disorder characterized by feelings of sadness and hopelessness that can interfere with normal life and in extreme cases, lead to suicide.

Among the most surprising results of the study, according to the researchers, was that incidence of depression seems to hold steady for people with brain injuries even years later.

“No matter what time frame you picked to study TBI and depression, whether 3-6 months (after the injury,) 12 months, or 5 years, around 30 percent of people always had depression,” said Dr. Oscar Guillamondegui, study co-author and professor in Vanderbilt’s Division of Trauma and Surgical Critical Care. “The prevalence in the general population is 9 or 10 percent.”

The study didn’t show a distinction between mild and severe injuries, meaning a patient who has had a simple concussion might be just as likely to develop depression as one with a fractured skull and severe bleeding on the brain.

That means military and civilian doctors alike need to educate patients and their families about possibilities of problems in the future, said study co-author Melissa McPheeters, a health-care epidemiologist and co-director of Vanderbilt’s Evidence-based Practice Center.

“Nine months out, they may have developed depression as a result of the injury, but because the injury seemed mild they may not have had a visit with a physician who could pick up on the problem,” McPheeters said.

However, she said, there’s no research to indicate whether TBI-related depression should be treated differently than depression arising from other causes.

McPheeters said the military has great opportunities to contribute to greater knowledge of the TBI-depression link because of its high numbers of patients with brain injuries and because of its ability to track servicemembers who have been treated.

Military TBI experts say depression is just one of the conditions that can be associated with brain injury among troops. Others include post-traumatic stress disorder, substance abuse, chronic headaches and sleep disorders, all of which combine to make it difficult to draw a straight line between the two conditions in a military environment.

“We see a large amount of depression in servicemembers who have TBIs,” said Air Force Col. Stephen Sharp, who develops clinical standards for TBI at the Defense Centers of Excellence for Psychological Health and Traumatic Brain Injury. “But in our population we have the complication of a fair amount of psychological health issues that happen as a result of being deployed in combat situations.”

The Defense Centers of Excellence has issued guidelines to doctors telling them to be aware of the possibility of depression, as well as other conditions, among troops with brain injuries, Sharp said.

“We acknowledge they occur frequently together, but is one causing the other?” he said. “That’s a much tougher issue to deal with.”

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