Can a Concussion Lead to Depression Years Later?

A recent study looks at how a head injury can lead to depression years after the health issue has healed.

According to researchers from the Institute for Behavioral Medicine Research, this could help explain some of the midlife mental-health issues that certain individuals suffer who have also undergone many concussions as young adults. Researchers note that many of these depressive symptoms are likely to be inflammation-related.

An added complication to the problem is that aging already increases brain inflammation following a traumatic brain injury (TBI) experience, caused by a magnified immune response of "secondary changes," such as a second head injury, infections or other stressors.

Scientists looked at mice to monitor these high-alert cells in the brain, known as the microglia. They showed an exaggerated response to an immune challenge one month after a moderate brain injury. The increased brain inflammation formed with the development of depressive behaviors that were not observed in the uninjured mice.

"If we had waited three, six or nine months, the symptoms probably would have gotten even worse," said lead study author Jonathan Godbout, an associate professor of neuroscience at Ohio State University and researcher in the Institute for Behavioral Medicine Research, via a press release. "A lot of people with a history of head injury don't develop mental-health problems until they're in their 40s, 50s or 60s. That suggests there are other factors involved, and that's why we're looking at this two-hit idea-the brain injury being the first and then an immune challenge. It's as if one plus one plus one equals 15. There can be a multiplier effect."

The researchers compared uninjured mice with mice that had experienced a moderate TBI. The injured mice showed initial coordination problems that resolved within a week. The injured mice also showed signs of depressive symptoms that gradually improved in one month. Researchers believe this is due to the expected neuroinflammation that occurs during a traumatic brain injury.

Thirty days following injury, researchers examined the brains of the injured mice to determine whether immune cells had remained on high alert following the injury. This is what they found:

"The young adult mice that have a diffuse head injury basically recover to normal, but not everything is normal," Godbout said, via the release. "The brain still has a more inflammatory makeup that is permissive to hyperactivation of an immune response."

His lab is now currently investigating potential treatments that could either help or prevent priming of the microglia-the first line of defense that help protect brain cells after injury-immediately following an injury.

More information regarding the study can be found here.