The Genetics of Concussion Recovery

genetic-concussionOf the more than 2.5 million concussions that occur every year in the US (source: CDC), the majority of people who have concussion symptoms can typically return to normal activities within 10 days to a few weeks after the event that caused the concussion.

For an unfortunate minority, however, concussion symptoms such as headache, dizziness, fatigue, irritability, impaired memory, and insomnia can last for months or years in a condition known as post-concussion syndrome (PCS).

The risks for PCS include a prior history of concussions, prior history of depression and anxiety, and an emerging concept of personal genetics.

A Definition of Concussion

A concussion is a type of brain injury caused by a bump, blow, or jolt to the head or by a hit to the body that causes the head and brain to move rapidly back and forth. This sudden movement can cause the brain to bounce around or twist in the skull, stretching and damaging the brain cells and creating chemical changes in the brain:

These chemical changes in the brain cause an acute energy crisis in the brain, resulting in lowered glucose metabolism (the brain’s fuel) for a period of 7-10 days post-concussion.

In addition, glutamate, glutamine, and choline levels rise in the brain after a concussion. Especially for people with a history of multiple concussions, elevated levels of these chemicals are indicative of neuroinflammation and diffuse axonal injury.

Can Your Genes Affect Concussion Recovery?

The emerging answer appears to be yes. Although concussion genetics research is still very new, current evidence points to a number of genetic variants that can influence concussion recovery, including the apolipoprotein E (“APOE”) gene, and the GRIN2A gene.

The APOE gene, which codes for a protein that is involved in brain recovery after injury, has three variants: E2, E3, and E4. People with the E4 variant (about 25% of the population) who sustain a concussion may be at greater risk for experiencing post-concussion symptoms, according to ongoing research.

The GRIN2A gene codes for a protein that works with the NMDA receptor, which is involved in controlling neurotransmission, synaptic plasticity and memory function. Recent research points to the possibility that different variants of the GRIN2A gene can dramatically affect post-concussion recovery times.

Both the APOE and GRIN2A genes already have established links to increased risk for other brain disorders – GRIN2A for epilepsy, and APOE for Alzheimer’s disease, so there is probably a good degree of overlap for “latent” cognitive problems and “acute” events like concussion.

Looking into the future, we will probably see the concept of “concussion-resistant” vs. “concussion vulnerable” genetic profiles, which will inform parents, coaches, and employers on the suitability of an individual to a particular sport or high risk job (think firefighter, military roles).

The future probability of genetic profiling will also bring up a host of legal, ethical, and public policy issues that will need to be acknowledged and addressed in the years ahead.