Post concussion syndrome after a car crash: what it is, how long it lasts and how it is diagnosed
Know what lingering concussion symptoms look like and what your care team checks
It has been six weeks since the crash. The bruises are gone and the car has been repaired. Still, a headache creeps in most afternoons, and you read the same email three times before it sinks in.
Maybe the scan at the emergency room was normal, and someone called your injury a mild concussion. Mild can feel like the wrong word when you cannot get through a workday. You may wonder if something was missed, or if people think you are exaggerating.
This guide describes what post concussion syndrome is, how long it tends to last, how it is diagnosed and which warning signs need care right away.
What post concussion syndrome means
Medical teams classify a concussion as a mild traumatic brain injury, or mild TBI. The American Congress of Rehabilitation Medicine (ACRM) published updated rules for diagnosing mild TBI in 2023 [7]. They are meant for children and adults, and for injuries in sports, the military and everyday civilian life, such as crashes [7]. The expert panel agreed that the words concussion and mild TBI can mean the same thing when brain scans come back normal or were never needed [7]. The criteria also let blood tests and tests of thinking, balance and vision count toward the diagnosis [7].
For most people, concussion symptoms ease within about two weeks [1]. Post concussion syndrome, often shortened to PCS, describes the people whose symptoms hang on longer. No single scan or blood test confirms it. A care team pieces it together from when your symptoms began, how they have changed, and what else might explain them.
The names you may see
In the United States, the diagnosis code used on medical records and bills is F07.81, titled postconcussional syndrome [8]. A clinician can add a separate code when posttraumatic headache is part of the picture [8]. Researchers often say persistent postconcussion symptoms [5]. A VA and Department of Defense guideline from 2021 uses the phrase persistent symptoms attributed to mild TBI [9].
Why the terms keep changing
The fourth edition of the DSM, a psychiatric manual, required symptoms to last at least 3 months [5]. It also called for test results showing memory or attention problems [5]. The ICD-10 rules required neither one, and the newer DSM-5 left postconcussional disorder out [5].
Because the rules differ, estimates of how many people have PCS range from 11% to 82% [5]. In one study group, 64% met the ICD-10 definition at 3 months, but only 11% met the older DSM one [5]. Current guidelines tend to set a time point, around one month, and then look at each symptom on its own [2, 9].
Comparison compiled by Safety Behind the Wheel Foundation
Names and time frames compared
| Term | Where it is used | Time frame |
|---|---|---|
| Persisting symptoms | Amsterdam sport consensus, all ages | More than 4 weeks |
| Prolonged symptoms | Living Concussion Guidelines, adults | More than 1 month |
| Persisting symptoms | 2025 Action Collaborative guideline, adults | Beyond 30 days |
| Postconcussional disorder | Older DSM manual (fourth edition) | At least 3 months |
| Postconcussional syndrome | ICD-10 (US code F07.81) | No 3 month minimum |
| Persistent posttraumatic headache | ICHD-3 headache criteria | More than 3 months |
Sources: Patricios et al. [4]; Living Concussion Guidelines [2]; Silverberg et al. 2025 [3]; Polinder et al. [5]; AAPC [8]; ICHD-3 [10].
Symptoms that tend to linger
The CDC says concussion symptoms can change how you feel, think, act or sleep [1]. A tool many clinics use, the Rivermead Post Concussion Symptoms Questionnaire, asks about 16 common symptoms [11].
- Headache, which a 2025 guideline names among the most common problems to treat first [3]
- Dizziness and balance trouble [1, 11]
- Vision problems, including blurred or double vision [11]
- Sleep changes, such as sleeping more or less than usual or struggling to fall asleep [1]
- Fatigue, or tiring more easily than before [11]
- Thinking problems, such as poor focus, forgetfulness or taking longer to think [11]
- Mood changes, such as irritability, worry, sadness or frustration [1, 11]
- Sensitivity to light and noise [1]
Some symptoms start at once. Others surface hours or days later [1]. The CDC notes that a week or two after the injury, you may feel more emotional or have trouble sleeping [1].
These symptoms are not unique to brain injury. People hurt in other ways, and even healthy adults, report many of them too [5]. The Living Concussion Guidelines warn that lingering symptoms can be vague and can overlap with other conditions [2]. A care team weighs when each symptom started and what else could explain it.
A hypothetical example
Imagine a 34 year old warehouse supervisor who was hit from the side at an intersection. In the first week, her neck hurt most. By week three, the beeping of forklifts brought on headaches, and she was awake at 2 a.m. most nights. Each problem seemed small alone, but together they made a full shift feel impossible.
How long symptoms usually last
The answer depends on who was studied and how symptoms were counted.
Among athletes of all ages, a full return to sport usually happens within a month, according to the 2022 Amsterdam sport consensus [4]. A Toronto study followed adults from the general public who went to an emergency room with a concussion, leaving out crash and workplace injuries. They generally recovered over 4 to 12 weeks, which the authors note is longer than reports on athletes [12].
For adults in general care, the Living Concussion Guidelines estimate that 15% to 20% still have symptoms past one month [2]. Another part of the same guideline cites about 20% to 30% [2]. The 2025 Action Collaborative guideline says up to 1 in 3 adults [3].
Studies of people treated in hospitals have reported higher numbers. In a Canadian study of adults seen at three emergency departments, 40% still had symptoms at 90 days [13]. Concussions from car crashes were more likely to last [13]. In the European CENTER TBI study, about 39% of people with mild TBI were hurt in road traffic crashes [14]. Between one third and close to half met a symptom based definition of PCS at 3 and 6 months [14]. A stricter scoring rule cut those rates by about half [14].
Comparison compiled by Safety Behind the Wheel Foundation
How many people still have symptoms, by study
| Who was studied | Time point | What researchers found |
|---|---|---|
| Athletes of all ages | About 1 month | Most back to full sport |
| Adults from the general public, crash injuries excluded | 4 to 12 weeks | Recovery generally took this long |
| Adults at 3 Canadian emergency departments | 90 days | 40% still had symptoms |
| Mild TBI patients at European trauma centers | 3 and 6 months | 34% to 46% met a PCS definition |
| Mild TBI patients at 11 US trauma centers | 12 months | 53% reported some limits, vs 38% with other injuries |
Sources: Patricios et al. [4]; Comper et al. [12]; Rowe et al. [13]; Voormolen et al. [14]; Nelson et al. [15]. Studies used different measures, so compare with care.
What the one year numbers mean
The US TRACK TBI study enrolled about 1,450 patients at 11 level I trauma centers, including a group with orthopedic injuries but no head injury [15]. At 2 weeks, 87% of people with mild TBI reported some limits in daily life [15]. By 12 months, that share fell to 53%, compared with 38% of the orthopedic group [15].
It measured daily function, and its patients came from major trauma centers, so the results may not match people seen only at urgent care. One research review of many studies estimated that symptoms last over the long run in about 10% to 25% of people with mild TBI [5].
Who is more likely to have lasting symptoms
Research points to factors linked with a slower recovery, though none can predict yours for certain. The 2025 Action Collaborative guideline suggests clinicians screen for them and consider specialty care for people at high risk [3].
Factors before and at the time of injury
- A high load of symptoms in the first days, which two expert groups call the strongest predictor [3, 4]
- A history of migraine, a mental health condition or past concussions [3]
- Female sex, which many studies link to more reported symptoms [3, 5]
- Age over 65, which the Living guideline lists as a risk factor [16]
- Signs of a more serious brain injury, such as a lower Glasgow Coma Scale score or an injury seen on a brain scan [3]
A history of repeated concussions is linked to a longer recovery [6]. In athletes, poor sleep in the first 10 days and delays in getting care were also tied to slower recovery [4].
Factors linked to crashes
The Living Concussion Guidelines note that injuries outside sport can be sudden and upsetting, and may come with other injuries, some of them serious [2]. In the Canadian emergency study, crash related concussions were more likely to bring lasting symptoms [13].
A review of 281 records from one outpatient concussion clinic compared crash, workplace and sports concussions [17]. People hurt in crashes or at work came to the clinic later, stayed in care longer and reported poorer physical and mental health [17]. The authors suggested these groups may need different care plans and expectations [17].
Insurance claims and lawsuits can add stress during recovery. One research review advises clinicians to ask about legal matters, along with social support and other life stress, as part of a full assessment [5]. If you have a claim, read your own policy and check with your state insurance department, since rules differ by state and by policy.
Conditions that overlap with post concussion syndrome
Several other conditions cause similar complaints, and each has its own treatment.
Whiplash and neck injury
Whiplash happens when the head is thrown forward and back, bending the neck [10]. Researchers who studied people with chronic whiplash wrote that its symptoms overlap a great deal with PCS [18]. Whiplash can bring neck pain, dizziness, fatigue and thinking problems [18]. The same authors noted that after a crash, care often centers on the neck, and a concussion can be missed [18]. The Living Concussion Guidelines advise a physical exam of the head and neck when headache lingers [2].
Posttraumatic headache
Under the ICHD-3 headache criteria, headache is called persistent when it begins in the first week after a head injury and is still present after 3 months [10]. The 7 day window is somewhat arbitrary, and appendix criteria allow for later onset [10]. When these headaches drag on, the criteria say to consider medication overuse headache [10].
PTSD, depression and anxiety
Some PCS symptoms resemble the hyperarousal of posttraumatic stress disorder (PTSD), that tense, always on guard feeling [5]. Nearly half of people with lasting PCS symptoms had depression or anxiety before the injury, according to one review [5]. The 2025 guideline makes a strong recommendation that clinicians check for mental health conditions after a TBI, both new ones and older ones that have flared [3]. The VA and Department of Defense guideline suggests that these conditions be assessed and treated the same way, with or without a brain injury [9].
Sleep, pain, balance and vision problems
The Living Concussion Guidelines list chronic pain and sleep disorders among the conditions to rule out [2]. They also call for checking the vestibular system, which means your inner ear balance system, along with eye movements [2].
How post concussion syndrome is diagnosed
Your story
Expect questions about the crash, when each symptom started, and how it has changed. Your care team will likely ask about past concussions, migraine and mental health [3]. The Living guideline advises a review of all medicines, along with supplements, alcohol and cannabis [2].
A symptom questionnaire
Guidelines advise a standard symptom scale at each follow up visit until symptoms improve or level off [2]. On the Rivermead questionnaire, you rate 16 symptoms over the last 24 hours, compared with how you were before the accident [11]. Each one gets a score from 0, not experienced, to 4, a severe problem [11]. Repeat scores can show progress that is hard to see day to day.
A focused exam
The Living guideline advises checking your most bothersome problems directly [2]. That can include the head and neck, balance and eye movements, mood, sleep and thinking [2].
Tests that help, and tests that usually do not
The 2025 guideline says clinicians should not order a CT or MRI scan for every patient, though they may order one when something seems unusual [3]. Older adults on certain blood thinners are a special case and should get imaging right away after a new injury [16]. The VA and Department of Defense guideline suggests against computer based concussion test batteries for routine diagnosis [9].
If thinking problems last more than a month, the 2025 guideline says a formal neuropsychological assessment may be offered [3]. This is a longer set of thinking and memory tests. It can help plan a return to work, school or sport [3].
Before your appointment
Checklist from Safety Behind the Wheel Foundation
- Write down each symptom and the date it started.
- Keep a simple daily log for one to two weeks, scoring each symptom from 0 to 4.
- Note crash details, such as where you sat and whether your head hit anything.
- List past concussions, migraine and mental health history.
- Bring every medicine and supplement, and be honest about alcohol and cannabis.
- Ask for copies of any scans or reports from the emergency room.
- Bring someone who has noticed changes in you since the crash.
When to get help and who to see
Most people start with their primary care practice. The VA and Department of Defense guideline suggests this kind of symptom focused care, led by primary care [9]. If you still have symptoms at one month, a referral to a specialist or a team based concussion clinic may be needed, according to the Living guideline [2]. The 2025 guideline suggests that specialty care be considered when someone has a high risk of long recovery [3].
Depending on your symptoms, your team may suggest vestibular rehabilitation for dizziness and balance problems [3, 9]. Thinking problems may lead to neuropsychological testing, and mood symptoms call for screening and treatment [3].
Get emergency care right away
Dial 911, or have someone drive you to the nearest emergency department, if you notice any of the CDC danger signs below [1].
- Head pain that builds in strength and will not fade
- Weakness, numbness, decreased coordination, convulsions or seizures
- Vomiting again and again
- Slurred speech or unusual behavior
- One pupil larger than the other
- Being confused, restless or agitated, or unable to recognize people or places
- Losing consciousness, looking very drowsy, or not being able to be woken up
Questions to ask your care team
Question checklist from Safety Behind the Wheel Foundation
- Do my symptoms fit post concussion syndrome, or could something else explain them?
- Which symptom should we work on first?
- Should my neck be checked for whiplash injury?
- Do I need a balance and eye movement exam?
- Is a CT or MRI needed in my case, and why or why not?
- Should I fill out a symptom questionnaire at each visit to track progress?
- Would neuropsychological testing help me plan my return to work?
- Should I be screened for depression, anxiety or PTSD?
Frequently asked questions
Can post concussion syndrome start weeks after a crash?
Some symptoms can appear hours or days later, and mood or sleep changes may surface a week or two after the injury [1]. Headache criteria usually expect posttraumatic headache to begin within 7 days, though they allow for later onset [10]. Tell your care team about any new symptom, since other conditions can look similar [2].
Will I need an MRI or CT scan?
Probably not. The CDC says a concussion can be spotted without one, though scans may be used when bleeding is a worry [6]. The 2025 guideline advises against scanning every patient and saves it for unusual features [3].
Is post concussion syndrome permanent?
For most people, no. One review estimates that symptoms last over the long run in about 10% to 25% of people with mild TBI [5]. Even then, guidelines call for care aimed at each symptom [9].
Does stress mean my symptoms are not real?
No. The sport consensus says lasting symptoms may come from the concussion, from conditions present before it, or from both [4]. Guidelines advise checking for stress, sleep problems and pain, since each can add to symptoms and has its own treatment [2, 3].
The bottom line
Recommendation from Safety Behind the Wheel Foundation
Post concussion syndrome is a set of real, common symptoms that outlast the usual recovery from a concussion. Most people improve within weeks, but a sizable share of adults, especially after crashes, still have symptoms at one to three months [3, 13].
A clear record of your symptoms gives your care team the most to work with, and not every adult needs a scan [2, 3]. Ask whether your neck, balance, vision and mood have been checked, and get emergency care for any danger sign [1]. If you have an insurance claim, keep copies of your records, read your own policy and check with your state insurance department.
Sources and further reading
- 1Centers for Disease Control and Prevention. Symptoms of mild TBI and concussion. Updated September 2025. cdc.gov/…/signs-symptoms/index.html
- 2Living Concussion Guidelines (Ottawa Hospital Research Institute). Diagnosis/assessment of prolonged symptoms. Updated April 2023. concussionsontario.org/…/diagnosis-assessment-of-prolonged-symptoms
- 3Silverberg ND, Lee K, Mikolić A, et al. Action Collaborative on Traumatic Brain Injury Care: adapted clinical practice guideline. Annals of Family Medicine. 2025;23(6):552-569. doi.org/10.1370/afm.250352
- 4Patricios JS, Schneider KJ, Dvorak J, et al. Consensus statement on concussion in sport: the 6th International Conference on Concussion in Sport, Amsterdam, October 2022. British Journal of Sports Medicine. 2023;57(11):695-711. doi.org/10.1136/bjsports-2023-106898
- 5Polinder S, Cnossen MC, Real RGL, et al. A multidimensional approach to post-concussion symptoms in mild traumatic brain injury. Frontiers in Neurology. 2018;9:1113. doi.org/10.3389/fneur.2018.01113
- 6Centers for Disease Control and Prevention. About mild TBI and concussion. Updated September 2025. cdc.gov/traumatic-brain-injury/about/index.html
- 7Silverberg ND, Iverson GL, et al. (ACRM Brain Injury Special Interest Group Mild TBI Task Force and ACRM Mild TBI Diagnostic Criteria Expert Consensus Group). The American Congress of Rehabilitation Medicine diagnostic criteria for mild traumatic brain injury. Archives of Physical Medicine and Rehabilitation. 2023;104(8):1343-1355. doi.org/10.1016/j.apmr.2023.03.036
- 8AAPC. ICD-10-CM code F07.81: Postconcussional syndrome. Accessed October 2026. aapc.com/codes/icd-10-codes/F07.81
- 9U.S. Department of Veterans Affairs and Department of Defense. VA/DoD clinical practice guideline for the management and rehabilitation of post-acute mild traumatic brain injury, version 3.0. Provider summary. 2021. healthquality.va.gov/…/VADoDmTBICPGProviderSummaryFinal508.pdf
- 10International Headache Society. ICHD-3: 5.2 Persistent headache attributed to traumatic injury to the head. Accessed October 2026. ichd-3.org/…/5-2-persistent-headache-attributed-to-traumatic-injury-to-the-head
- 11King N, Crawford S, Wenden F, Moss N, Wade D. Rivermead Post-Concussion Symptoms Questionnaire. Journal of Neurology. 1995;242:587-592. Form hosted by WSIB Ontario, dated June 2008. wsib.ca/…/mtbi_rivermead.pdf
- 12Comper P, Foster E, Chandra T, et al. The Toronto Concussion Study: a prospective investigation of characteristics in a cohort of adults from the general population seeking care following acute concussion, 2016-2020. Frontiers in Neurology. 2023;14:1152504. doi.org/10.3389/fneur.2023.1152504
- 13Rowe BH, Yang EH, Gaudet LA, et al. Sports-related concussions in adults presenting to Canadian emergency departments. Clinical Journal of Sport Medicine. 2022;32(5):e469-e477. doi.org/10.1097/JSM.0000000000001005
- 14Voormolen DC, Haagsma JA, Polinder S, et al. Post-concussion symptoms in complicated vs. uncomplicated mild traumatic brain injury patients at three and six months post-injury: results from the CENTER-TBI study. Journal of Clinical Medicine. 2019;8(11):1921. doi.org/10.3390/jcm8111921
- 15Nelson LD, Temkin NR, Dikmen S, et al. Recovery after mild traumatic brain injury in patients presenting to US level I trauma centers: a Transforming Research and Clinical Knowledge in Traumatic Brain Injury (TRACK-TBI) study. JAMA Neurology. 2019;76(9):1049-1059. doi.org/10.1001/jamaneurol.2019.1313
- 16Living Concussion Guidelines (Ottawa Hospital Research Institute). Older adults. Updated July 2025. concussionsontario.org/…/older-adults
- 17McPherson JI, Nowak A, Chizuk H, Leddy JJ, Haider MN. Differing clinical characteristics among individuals with concussions sustained at work, in motor vehicle collisions, and sport. Brain Injury. 2025;39(5):420-426. doi.org/10.1080/02699052.2024.2441846
- 18Callan B, Vintimilla A, Gulla N. Subtle ocular motor deficits in people with chronic whiplash associated disorder compared to healthy controls. Frontiers in Neurology. 2025;16:1676654. doi.org/10.3389/fneur.2025.1676654
This article reflects the safety priorities of concussion recovery and road safety education. It offers general education, not medical or legal advice, and it cannot diagnose your symptoms. Guidance on lasting concussion symptoms is updated often, so check official sources such as the CDC and talk with your own care team about your situation. Reviewed October 2026.
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