Concussions that occur in the teen years increase the risk of adult-onset multiple sclerosis (MS) in people with a genetic susceptibility to the disease, according to a new study published in the journal Annals of Neurology. No link was found between MS and concussion in younger children.

MS is a disease in which the body’s immune system attacks parts of the central nervous system. It is caused by a combination of genetic susceptibility and other factors that are incompletely identified.

The new findings show just how important it is to protect teenagers from head injuries. “Bicycle helmets is one way, and we should consider head injury risk in sports played by adolescents,” says Professor Scott Montgomery at Örebro University in Sweden.

The research comes from a collaborative study between Örebro University and Karolinska Institutet, which showed concussion in adolescence increased the risk of MS in later life by 22 percent for one concussion. Teens who experienced two or more concussions were at more than a doubled risk of MS at 133 percent. But not all teenagers run the same risk.

“MS is caused by a combination of genetic susceptibility and environmental exposures. Most of the young people who experience a head trauma should not worry as they will not carry the necessary genes and other risks that will result in MS in later life,” says Montgomery.

The researchers used medical records to identify children and adolescents who had been treated for concussion in the hospital. They divided the subjects into two groups: birth to age 10 years and adolescents from ages 11 to 20. The risk of MS in later adulthood was examined for both groups.

“We think that concussion among adolescents can indicate the processes that cause the body’s immune system to attack the insulating layer of nerve cells which, over time, prevents them from functioning correctly,” says Montgomery.

Differences in brain development during childhood and adolescence may shed some light on why concussion in these two age groups does not carry the same risk of subsequent MS.

“The rapidly developing brain in earlier childhood may be more able to avoid some delayed consequences of trauma than in later teenage years,” explains Montgomery.

He believes these new findings strengthen the arguments to protect young people from head injury. “Teenagers often take risks, like cycling without a helmet. If they knew about the possible long-term consequences, they might think again; perhaps they wouldn’t think it’s so cool to ride without a helmet,” he says.

Still, Montgomery adds that he absolutely does not want young people to avoid sports and physical activity. “We should consider ways to reduce the risk of head injury, especially repeated head injuries, when participating in sport.”

Next, the researchers plan to study genetic influences, including how genes interact with other factors to determine MS risk. This will involve looking at how genes influence the risk of MS associated with concussion in adolescence, as well as examining other exposures among teenagers, such as infections.

Source: Örebro University