Teens with a history of concussions are more than three times as likely to suffer from depression as teens who have never had a concussion, finds a new study in the Journal of Adolescent Health.

"What this study suggests is that teens who have had a concussion should be screened for depression," said lead study author Sara Chrisman, M.D., a pediatrician at Seattle Children's Hospital.

Concussion, considered a mild traumatic brain injury, can also have serious psychological effects. Most prior research on these psychological effects has focused on adults. However, many teens experience concussions through sports injuries or accidents, and less is known about long-term complications in adolescents.

The study used data from the 2007-2008 National Survey of Children's Health and included health information from over 36,000 adolescents ages 12 to 17. 2.7 percent of the sample had had a concussion and 3.4 percent had a current depression diagnosis.

Teens who were 15 years or older, lived in poverty or who had a parent with mental health problems were more likely to be depressed than other teens, said Chrisman, "but what was surprising was when we took those factors into consideration, it didn't take away from the association between depression and a history of concussion."

Chrisman also cautioned that it's not known what exactly might account for higher rates of depression in teens with a history of concussion. It could be the brain injury itself, diagnostic bias due to repeated medical visits for concussion, doctors mistaking symptoms of a concussion for depression, or from the social isolation that they may experience while recovering.

Jeffrey Max, M.D., a psychiatrist who specializes in psychiatric outcomes of traumatic brain injury in children and adolescents at the University of California, San Diego noted, "In our research, we've found that about 10 percent of the kids had a full depressive disorder or subclinical depressive disorder 6 months after a concussion." Children who have a history of concussion are more likely to develop attention-deficit/hyperactivity disorder (ADHD) and have difficulties controlling their moods, especially anger, rather than experience depression, Max added.

Unlike Chrisman, however, Max observed that the actual brain injury associated with concussions is probably a major cause of depression in the first few months after injury. "In the clinic, we've certainly seen cases where within hours [of sustaining a concussion], a kid who's never had depression before is suddenly depressed and suicidal. One of our studies found that the brain images in children with traumatic brain injury and depression were actually quite similar to those seen in adults who develop depression as a result of traumatic brain injury."