Yes, a concussion is a traumatic brain injury. Specifically, it’s classified as a mild traumatic brain injury (mTBI), the most common type of TBI. The word “mild” refers to the fact that concussions are typically not life-threatening, not that their effects are insignificant. The CDC uses the terms “mild TBI” and “concussion” interchangeably.
Why Concussions Are Classified as Brain Injuries
A concussion happens when a bump, blow, or jolt to the head (or a hit to the body) causes the brain to move rapidly inside the skull. That sudden movement can make the brain bounce against the skull’s interior or twist, stretching and damaging brain cells. The injury also triggers a cascade of chemical changes inside the brain, disrupting its normal metabolism. In the initial hours after a concussion, the brain burns through glucose at an abnormally high rate before dropping into an energy-depleted state.
This is a real biological injury, even though standard CT scans typically appear normal in concussion patients. Even MRI, which provides more detailed images, often cannot detect the microscopic damage involved. That’s part of what makes concussions tricky: the injury is functional and chemical rather than structural, so it doesn’t show up on the imaging tools most emergency departments rely on.
How Severity Is Measured
Doctors use a scoring tool called the Glasgow Coma Scale (GCS) to classify brain injuries by severity. It measures eye opening, verbal responses, and motor responses on a scale of 3 to 15. A concussion, or mild TBI, falls in the 13 to 15 range. Moderate TBIs score 9 to 12, and severe TBIs score 3 to 8. Most people with a concussion score at or near 15, meaning they’re alert and responsive, which is exactly why the injury can be easy to underestimate.
What a Concussion Feels Like
Concussion symptoms span four broad categories: physical, cognitive, emotional, and sleep-related. They don’t always appear immediately, and some develop over hours or days.
Physical symptoms are usually the most noticeable. Headache is the most common, followed by dizziness, nausea or vomiting, blurred vision, ringing in the ears, fatigue, and sensitivity to light and noise. Some people notice changes in taste and smell.
Cognitive symptoms include feeling foggy or confused, difficulty concentrating, memory problems, and amnesia around the event itself. Others may notice you seem dazed, respond slowly to questions, or repeat yourself. Temporary loss of consciousness can happen but doesn’t occur in most concussions.
Emotional and sleep symptoms round out the picture. Irritability, personality changes, and feeling unusually emotional or depressed are common. Sleep disturbances, whether sleeping too much or too little, frequently follow a concussion as well.
Typical Recovery Timelines
Most children with a concussion feel better within two to four weeks. Adults generally follow a similar or slightly shorter timeline, though individual recovery varies widely depending on the severity of the injury, whether it’s a first concussion or a repeat one, and factors like age and overall health. If symptoms persist beyond that four-week window, a specialist with experience in brain injury management can help guide the next steps.
Early recovery involves a brief period of relative rest followed by a gradual return to normal activities. The most recent international consensus on sport-related concussion, published after the 6th International Conference on Concussion in Sport in 2022, outlines a stepwise approach that includes returning to learning and cognitive tasks before returning to physical activity. The framework emphasizes that recovery isn’t just about physical symptoms resolving. Cognitive and emotional function need to recover too.
Why “Mild” Can Still Be Serious
The “mild” label leads many people to brush off concussions, but there are real risks, especially with repeat injuries. Second impact syndrome occurs when someone sustains another concussion before fully recovering from the first. It causes rapid, severe brain swelling that is frequently fatal. Between 1984 and 1995, the CDC documented 21 cases, most involving male adolescents or young adults in contact sports like football, boxing, ice hockey, and skiing. The true number is likely higher since cases often go unreported or unrecognized.
Even without a second impact, repeated concussions over time are linked to longer recovery periods and potentially lasting effects on thinking, mood, and behavior. The 2022 international consensus statement specifically added “retire” to its management framework, acknowledging that athletes with a history of multiple concussions sometimes need to make career-ending decisions to protect their long-term brain health.
Signs That Suggest Something Worse
While most concussions resolve on their own, certain symptoms suggest a more severe brain injury that needs immediate emergency care. Repeated vomiting after a head injury is one red flag. Others include worsening headache, seizures, weakness or numbness in the limbs, increasing confusion, slurred speech that gets worse over time, and one pupil appearing larger than the other. Any of these signs can indicate bleeding or swelling inside the skull, which is a medical emergency, not a concussion that can be managed at home.