One minute I was waving hello to the neighbors during a typical Rollerblading session with my dog, and the next I was flying down a newly paved hill at a runaway speed. Aiming for a soft landing, I steered up a driveway toward a lawn. My feet hit the grass, and I flew about 10 feet through the air before landing and rolling on the ground. I had the wind knocked out of me—a truly painful experience I hadn't had since childhood—but I could tell I hadn't broken any bones. I was just congratulating myself on avoiding a serious injury when I passed out.

I didn't know it at the time, but this incident last fall was my personal introduction to the frightening and sometimes baffling experience of having a concussion. As a science editor, I had handled a number of stories on mild traumatic brain injury (TBI), as concussions are officially known, but I was not prepared for the pain and debilitation that came over the following weeks and months. That is because—for all its prevalence in the news as a danger to massive NFL players and tiny soccer tots alike—concussions remain subject to a remarkable amount of myth, mystery and misinformation. Even among well-meaning doctors. The good news is that concussion research has surged in recent years, thanks to concern from the athletic and military communities—so we are starting to learn more about the underlying causes of its symptoms and how best to treat them. And we are beginning to clear away some of the fog around who is at greatest risk for serious repercussions. Here are six key things you should know about concussions—things I wish I had known when I hit the ground.

1. You don't have to smack your head to get a concussion.

After my skating accident, I went to my local hospital because my abdomen hurt and one of my arms was rapidly swelling into a purple, football-sized balloon. The emergency room staff x-rayed my arm and did a CT scan of my midsection to rule out internal bleeding. As we were getting ready to go, my husband asked the doctor why he didn't assess me for a head injury. “Because she said she didn't hit her head,” the doctor replied. And that was that. I went home and went to bed.

The next morning the symptoms hit: excruciating headache, nausea, sensitivity to light, confusion. I thought I was having a bizarre and terrible migraine. I went the next day to see an associate of our family doctor, who promptly diagnosed me with a concussion. He reminded me that a sudden deceleration of the type I had undergone—from, say, 20 miles an hour to zero in less than a second—could damage the brain by causing it to slosh around within the skull.

In fact, doctors are seeing more and more concussions that do not involve a direct blow to the head, especially among military personnel exposed to bomb blasts. The shock wave from an explosion can send the brain bouncing perilously within the skull. Thousands of service members report concussions every year. Among U.S. civilians, the Centers for Disease Control and Prevention estimates about 1.36 million concussions a year. But that number is a bit shaky, in part because greater awareness of concussions has probably led more patients to seek medical attention and more doctors to notice and diagnose mild TBIs in recent years. As a result, the incidence has been rising.

Another reason the true incidence of concussions is not easy to pin down is that the diagnosis itself is based mostly on subjective symptom reporting [see “Do I Have a Concussion?” below] rather than any definitive test. Doctors diagnose a concussion if a person has had a blow or jolt to the head and reports at least a couple of the well-known symptoms, including dizziness, confusion, short-term memory loss, headache, and sensitivity to light or noise. But these symptoms can also be caused by a number of other factors, and unless there are clear neurological symptoms such as delayed pupil reflexes, which show up in some concussion cases, there is currently no way to know for sure whether symptoms are arising from a brain injury rather than, say, a migraine, the flu or post-traumatic stress disorder (PTSD). Most emergency room doctors will not order scans unless bleeding or more serious injury in the brain is suspected. Unlike these more dangerous complications, injury from a mild TBI is usually too microscopic for MRI, CT or PET scans to pick up.

There are simple steps to take if you do notice the telltale symptoms of concussion after you bump your head or after you are in any situation in which your head is jolted suddenly—including a fender bender or even a roller-coaster ride. “First, pull yourself out of risk so you don't hit your head again,” says William P. Meehan III, director of the Micheli Center for Sports Injury Prevention at Boston Children's Hospital. “Second, see a medical professional to get some guidance. And third, follow that guidance, which should be a few days of rest followed by gradually increasing activity.”

2. If you think you might have a concussion, make sure you don't hit your head again.

When the primary care doctor warned me about this risk, I thanked my lucky stars I had not decided to get back on my skates the day after my ER visit. Experts agree that minimizing the risk of a second concussion is key because getting two in a row can lead to long-term complications or, rarely, death. The mechanism behind this effect is unknown, but cell studies suggest it might have something to do with sodium.

The brain maintains a delicate balance of sodium and potassium ions to facilitate the electrical signals between neurons. When the head is jolted, cells react by suddenly taking up more sodium, which immediately shuts down the electrical signaling. That is why a concussion can cause a loss of consciousness so much faster than asphyxiation does. “It's a blackout of the brain's electrical grid,” explains Douglas H. Smith, director of the Center for Brain Injury and Repair at the University of Pennsylvania.

Experimental evidence is starting to suggest that one way brain cells react to this blackout is to quickly add more sodium channels along their membranes to help restore the balance. “That might be a great way to get the lights back on, but it also might come at a huge cost if you get hit again,” Smith says. With all that additional access to sodium now available, getting hit again “is like pouring saltwater over live circuits,” he says.

Many decades of studies in youngsters and adults confirm that suffering a second concussion while still experiencing symptoms from the first puts a person at a hugely increased risk for long-term symptoms lasting months or even years. In some rare cases, it can even lead to permanent brain damage or death. Second impact syndrome, as this most severe reaction is known, is diagnosed when a second concussion in the minutes, days or weeks following the first causes sudden and often fatal brain swelling. The exact mechanism behind this catastrophic cascade is unclear, but confirmed cases of second impact syndrome are fatal more than 50 percent of the time.

Most reported cases of the syndrome have been in children, prompting the strict guidelines regarding student athletes returning to play after sustaining a concussion. Prevalence is hard to measure because of the rarity of cases and the fact that the bleeding may be misdiagnosed as a direct result of the blunt trauma, but studies estimate that second impact syndrome kills about three to four people a year in the U.S.

3. It's okay to fall asleep after getting a concussion.

The familiar advice to keep a concussed person awake shows up in pop culture so often it has become a cliché. In reality, going to sleep a few hours after a concussion is fine and probably even helpful to your recovering brain. Here is what you should know about how much monitoring a concussed person truly needs.

Before brain-scanning technology, the only way to know if a blow to the head had caused a dangerous complication such as bleeding within the brain was to interact with patients in the minutes and hours after injury to see if their speech or motor coordination went downhill. Such interactions require a patient to be awake. That's all—there is nothing inherently dangerous about sleep, just the difficulty of assessing someone's neurological health if the person is unconscious.

Nowadays doctors can order a CT scan if major injury is suspected in the brain—for instance, if any bruising is visible under the scalp or if the patient has a severe and worsening headache. We also know a lot more about which symptoms are predictive of bleeding. In a landmark 2009 study published in the Lancet, physician Nathan Kuppermann of the University of California, Davis, and his colleagues studied 42,412 children and adolescents younger than 18. They found that for children older than two who did not have any of six specific symptoms, such as vomiting or dysfunctional cognition, there was a less than 0.05 percent chance of having a clinically important brain bleed or other dangerous complication. Four of these six symptoms did not correlate with dangerous complications when present in isolation without any of the other five. The two higher-risk symptoms, abnormal mental state as identified by the Glasgow Coma Scale or evidence of a skull fracture, suggest the need for a CT scan even in isolation.

The conclusion, as usual, is to get to a doctor as soon as possible so the call can be made about whether a CT scan or close observation is needed. But if the bump to the head was minor, and you're not sure it even caused a concussion, don't worry about falling asleep after a few hours have gone by. “Observing a person after head injury for four to six hours is a very helpful and useful strategy, but the advice to ‘wake a person up every so often to check on them’ is more aggressive than necessary,” explains physician Danny Thomas, a concussion researcher at the Medical College of Wisconsin. If the patient is breathing normally, not having a seizure, not vomiting or waking up with a worsening headache, there is no need to wake the person up fully and interact with him or her, Thomas says.

After six hours the danger has passed, according to much research. For example, a large Canadian study in 2010 in Pediatrics followed nearly 18,000 concussion patients and found that after six hours the chance that patients without altered consciousness or severely impaired cognition would have a brain bleed was 0 percent.

4. Prolonged “brain rest” is not necessary—and it may even be harmful.

When I finally saw that primary care physician and was diagnosed with a concussion, he told me to “rest my brain” for at least 10 days—no work, no socializing, no physical exertion, no reading or watching TV. I was instructed to lie in a dark room and perhaps listen to calm classical music if I could do so without my symptoms worsening. Needless to say, I became bored and frustrated very quickly. And I now know that such a long rest period probably did me no good—in fact, it may have slowed down my recovery.

My doctor is one of many—perhaps most—who advise patients to rest for a week or more based on outdated information that was never evidence-based in the first place. The original idea was to prevent a concussed athlete from getting back into the game too soon and risking a second concussion. Athletes are often so eager to get back on the field, Thomas says, that “they underreport and lie about symptoms.” Unfortunately, a recommendation intended to protect these overeager athletes got misapplied to the general public. “Athletes tend to recover much more quickly, so the timeline the experts had in mind was a couple of days,” says concussion researcher Noah Silverberg, a visiting assistant professor of medicine at Harvard Medical School. But people like me are often told to rest until their symptoms go away—which can be weeks or even months. “I think that's not what the original recommendation meant,” Silverman says.

Prolonged rest may not merely be boring, it flies in the face of what we know about healing an injured brain. “If someone has a stroke and then sits around and doesn't do anything, the person will never get better,” Thomas observes. He recently led one of the first randomized controlled clinical trials of varying rest periods in 88 concussed patients aged 11 to 22. He and his colleagues found that those who were put on strict rest—no school, no exercise, no screen time—for five days postinjury reported more symptoms at 10 days out than those who rested for only two days, according to results from the trial published in February 2015 in Pediatrics. The handful of other studies that have attempted to look at the effect of different activity levels postconcussion tend to line up with Thomas's findings—a day or two of rest following the injury is helpful but more than that is probably not.

Concussion experts believe there are several potential explanations for why more rest is not better. Sitting around thinking about symptoms can make them seem worse, for one. Moreover, when people are told they are too ill to do anything, they sometimes take on a sick role psychologically. It is even possible that resting too much causes a deconditioning of sorts in the brain, so that very little mental effort then triggers symptoms. “We need to take guidance from the physical therapy world: push up to the pain but not through it,” Thomas says. In other words, after the initial day or two of rest, a concussed person should try to go about daily life until symptoms show up and then stop, rest and repeat. Think of it as getting your brain back in shape.

5. Rest is not the only treatment available.

After enduring my interminable rest period, I tried to get back to work and discovered, much to my dismay, that reading anything on paper or a computer screen immediately triggered an excruciating headache and nausea. My physician had advised me to see a neurologist if I was still having symptoms after all that rest, so I did. The neurologist assessed my symptoms, offered some sympathy and prescribed sumatriptan, a migraine drug that has been shown to help ease postconcussion headaches and perhaps even speed up recovery. And that was it. I saw her every couple weeks; she verified that my symptoms were improving slowly and re-upped my prescription when necessary. Three months passed before I could tolerate a full day's work.

When I told this story to the various concussion experts I interviewed for this story, the universal reaction was disappointment but not surprise. “What you're describing is so common, so frustrating for patients and family,” Smith says. “You're shown out of the ER and left in the wind.” People with chronic symptoms end up diagnosing themselves, he says, and unfortunately many are never referred to a concussion specialist or clinic. Concussion clinics are becoming more common, especially in major metro areas and regions with large hospitals, and they usually bring together a team of practitioners that includes neurologists, psychiatrists, sports medicine or physiology specialists, and physical and occupational therapists. They offer a variety of physical and psychological treatments, many of which seem to successfully treat certain symptoms. Headache, memory and cognition issues, vestibular problems and visual symptoms—if only I had known!—are all treatable to some degree. Scientific data about the efficacy of these programs are scarce, however, because figuring out which concussion patients to enroll in trials—which ones will have a complicated recovery—is currently almost impossible, Smith says. Yet by borrowing treatments from other fields and specialties, concussion specialists are able to ease many symptoms.

The bottom line: “You can do something to speed up your recovery, especially if you're having a difficult time,” Silverberg says.

6. It's impossible to predict which symptoms a person will have and how long recovery will take—but that may change soon.

Up until a few years ago, doctors believed that being knocked unconscious indicated a more severe concussion than simply getting dazed. That idea is outdated. The majority of research findings have now shown that passing out has no relation to the severity of postconcussion symptoms or to recovery time. In fact, nothing about the incident seems to have any consistent predictive power—the type of accident, the location of the blow on the skull, the symptoms immediately following the event.

Recent research from Smith's team and others has finally homed in on an explanation for why some concussions are so much harder to recover from than others. These concussions, in addition to causing a sodium flood, do permanent damage to the brain's axons, the long tendrils that neurons use to communicate with one another and with different regions throughout the brain. In these more serious injuries, the sudden rotational acceleration caused by a blow or jolt to the head causes some axons to break. “Axons are like Silly Putty,” Smith says. “If you make a cylinder of Silly Putty and stretch it slowly, it will stretch forever. But if you take the same cylinder and stretch it rapidly, it snaps. That's what happens to axons under sudden rotational acceleration.”

When the axons break, they release a cascade of proteins and chemicals, some of which can trigger additional damage in nearby cells. Although the broken axons never grow back, the brain is adept at finding work-arounds and creating more connections—which is why even people with axon damage recover eventually.

One type of brain scan, called diffusion tensor imaging (DTI), is designed to specifically investigate the connections between cells—the axon tracts. As such, it has shown promise in small studies for identifying the extent of damage in a concussed patient's brain. Another promising diagnostic test looks for axon proteins in the blood, which can indicate the level of damage. Smith is hopeful that one or more of these techniques will be ready for use in larger studies fairly soon. “We're on the verge of developing much better diagnostics,” he says. “Then we can have highly powered studies, so we can look at drug therapies or other types of rehab strategies.”

A rash of brand-new studies are suggesting that certain red flags in the patient's medical history—migraine and motion sickness, for example—might be indicators that recovery will be arduous. But the most robustly supported risk factor is the presence of psychiatric symptoms, manifesting either before or after the concussion. Two studies in 2015, one that looked at 72 soldiers with blast-related injuries and the other that followed 77 civilians with sport- or accident-related injuries, both found that the presence of depression, post-traumatic anxiety and other mental symptoms predicted a prolonged recovery from concussion. A major review of the literature by Silverberg and his colleagues, published in April 2015 in the Journal of Neurotrauma, concurred: the factors that most robustly predicted a slow recovery were a history of mental health issues and postinjury anxiety.

“When a patient comes into a clinic, there are lots of questions asked about the nature of the injury, the mechanics, how and where you hit your head. As far as we know, none of that matters,” Silverberg says. “Clinicians should actually inquire about how concerned patients are about the fact that they've had a concussion and whether they've struggled with mental illness in the past.” As he points out, these data are cheap and easy to collect (unlike brain scans) and could be far more helpful in flagging people at risk for complications. Doctors should also try to be encouraging about patients' potential for recovery, he says—yet another reason why telling patients they must lie in a dark room for two weeks is counterproductive.

The last thing to note about concussion symptoms is that they can vary widely from one person to the next and even for the individual patient. During my recovery I found that one minute I could be conversing normally, even energetically, and the next I would suddenly feel sluggish, confused and nauseated. I heard many stories from the doctors and patients I interviewed about people being very suspicious or dismissive of patients' postconcussion struggles: bosses handing out pink slips, professors giving Fs, friends and family making accusations of malingering. People recovering from a concussion look totally normal, after all, and their symptoms are usually noticeable only to themselves.

“These are subtle deficits,” cautions Daniel Corwin, a concussion researcher and physician at Children's Hospital of Philadelphia. “We don't have objective tests, so we have to take the patient's report of symptoms at face value.” Corwin and other experts hope that recent media attention to concussions will lead schools, workplaces and the general public to recognize how difficult recovery can be. “It's tough,” he says. “And it's a great point for those in the community to consider.”

As for me, I have felt blissfully myself for several months now—except for a newfound nervousness about slipping on ice, falling off my bike or otherwise knocking my noggin. I hope I never have to go through the ordeal of a concussion again—but if I do, at least I now know more about how to help my brain heal.

Do I Have a Concussion?

If you have banged your head, been in a car accident or taken a spill, your doctor will probably assess you for a concussion. The diagnosis is not an exact science; a neurological examination might reveal issues with balance, reaction time or pupil dilation—but many concussions come without these obvious problems, or else these symptoms may have passed by the time of evaluation. For that reason, scientists are working feverishly to develop easy tests that can be conducted on the sidelines of a sports field to reliably identify a concussion no matter what symptoms are present. Many of these tests have shown promise in early trials, especially in cases in which a healthy comparison measurement is on file, making it easy for parents and coaches to quickly assess whether there has been a change in a player’s visual reaction time, counting or addition speed, or even ability to discriminate smells on a scratch-and-sniff card.

For those of us without reaction-time test results on file, however, doctors must rely heavily on the symptoms we report. One day blood tests or brain scans may be available, but right now the only common tool other than the neurological exam is a symptom inventory, such as the one below, developed by neuropsychologist Keith Cicerone. When doctors administer such surveys, they ask patients not only to indicate whether they have a given symptom but also to rate its severity (for example, on a 1 to 5 scale) and report how many days out of the past week it has occurred. Doctors mainly use such lists to track symptom burden over time. If mood, anxiety or sleep-related symptoms appear in the days or weeks after a brain injury, they can be a warning sign that a patient might be experiencing post-traumatic stress disorder or post concussive syndrome, which occurs when concussion symptoms linger for many months or even years. These inventories can also be helpful in the initial diagnosis—especially the first five symptoms, which are some of the classic signs of concussion. —K.S.S.

  • Feeling dizzy
  • Loss of balance
  • Poor coordination, clumsy
  • Headache
  • Nausea
  • Vision problems (blurring, trouble seeing)
  • Sensitivity to light
  • Hearing difficulty
  • Sensitivity to noise
  • Numbness or tingling on parts of body
  • Change in taste or smell
  • Loss of appetite or increased appetite
  • Poor concentration, easily distracted
  • Forgetfulness, not being able to remember things
  • Difficulty making decisions
  • Slowed thinking, difficulty getting organized, not being able to finish tasks
  • Fatigue, loss of energy, easily tired
  • Difficulty falling or staying asleep
  • Feeling anxious or tense
  • Feeling depressed or sad
  • Irritability, easily annoyed
  • Feeling easily overwhelmed by things