Just watching television footage of the terrorist attacks of September 11, 2001, was enough to cause clinically diagnosable stress responses in some people who did not even live near the attacks—let alone the millions of people who did.

Like many other major disasters, 9/11 brought with it a host of psychological repercussions, one of the most severe of which has been post-traumatic stress disorder. PTSD is characterized by trouble sleeping, difficulty controlling anger, losing interest in activities, flashbacks, emotional numbness and/or other symptoms. If not treated, it can be debilitating.

But these reactions are not uncommon after a major disaster—and teasing apart post-9/11 disorders has been tricky for psychologists and researchers. "We tend to use the terminology of PTSD very loosely. A lot of people will have traumatic reactions but not necessarily PTSD," says Priscilla Dass-Brailsford of Georgetown University Medical Center's psychiatry department.

Researchers have been poring over the piecemeal collection of studies conducted over the past decade on the conditions of people after the attacks—how they felt and how well various treatments, and the passage of time, have helped them overcome mental afflictions. And from the literature, we are learning that old styles of early intervention, such as debriefing sessions, are not as effective as once thought—and that more often than not, people are incredibly resilient and can recover on their own and should be given the opportunity to do so.

"Research on 9/11-related PTSD has challenged the ways in which mental health researchers assess exposure to trauma," Yuval Neria, of Columbia University's psychiatry and epidemiology departments, and his colleagues wrote in a new paper published in the September issue of American Psychologist. Those in the mental health field have also borrowed research from other traumatic events to better understand the psychological wounds inflicted by the terrorist attacks. "Despite the fact that the exposure is different, the symptoms and problems are more similar than some people think," Neria says of PTSD sufferers from natural disasters or combat.

The exception, not the rule

During the week after the September 11 attacks, Dass-Brailsford was on one of the first trains to New York City, where she conducted debriefing sessions with a large financial company that had had offices in the World Trade Center. Many of the workers she spoke with in those sessions "were really traumatized," especially those who had been the last persons that friends or colleagues had spoken to before they perished.

But not everyone who was at the scene of any of the attacks on the morning of September 11 wound up suffering from PTSD or an other severe stress response. In fact, the majority did not. After traumatic events, such as 9/11 or Hurricane Katrina, "people expect the survivors or the victims to have PTSD, but that's not necessarily the case," says Dass-Brailsford, who also worked as a psychiatric first responder in the week after Katrina. Even if people experience occasional anxiety or stress having "perfectly normal reactions," she explains.

"We cannot assume that everyone will have trauma reactions, Dass-Brailsford says. "We shouldn't be projecting that." Patricia Watson, of the National Center for Child Traumatic Stress at the University of California, Los Angeles, explains that labeling someone as needing help just based on their exposure also implies "that they don't have the resources to recover on their own, effectively undermining their own abilities and their chances of viewing themselves as a stronger person via having to solve their own problem."

Another reaction frequently projected on survivors of the attacks is the notion of survivor guilt. Although it is no longer recognized as a formal condition—now living, diagnostically, as a part of PTSD—it is especially common among those "who used to fight together or endure adversity together, such as firefighters, police officers or soldiers," Neria says. And for victims of 9/11, it is much more likely to play a role in overall PTSD if the affected individual survived and a close friend or colleague did not.

An uneven recovery

In general, the prevalence of PTSD tends to decline steadily in the months and years after a traumatic event, especially if people can get back to relatively normal routines. Research conducted in New York showed that the rates of PTSD among the general population eased from about 5 percent a year after the attacks to 3.8 percent two years later, according to work published in 2006 in The Journal of Nervous and Mental Disease.

Even many of the first responders and long-term cleanup workers seem to have largely recovered psychologically. But one group of workers has curiously not followed this trend: retired firefighters. In some studies, they seemed to have an increased prevalence of PTSD as time went on.

Some 22 percent of retired firefighters who responded on 9/11 were still suffering from PTSD some four and six years after the event, according to research published earlier this year in Public Health Reports.

Dass-Brailsford suggests that in addition to having to cope with the trauma of the event, having gone on disability or into early retirement "means that you're not working, you're not occupying your time, and you have more time to sit and think about what happened to you, so your reactions become stronger." Additionally, leaving behind a highly active and service-oriented job might result in a feeling that "you're not able to do anything meaningful," she says, which could add to depression and stress levels.

First responders of any type also rely on having delayed emotional reactions to best perform their stressful jobs. "They develop a capacity to contain their reactions so they can deal with it later" and get through the task at hand—whether it is rescuing people from a fire or pulling the injured from a car accident, Dass-Brailsford says.

And in the general population as well, "in the immediate aftermath of a traumatic event, a lot of people are numb," Dass-Brailsford explains. "For some people that state of shock and numbness can last a long time, sometimes for a number of years." After Katrina, for example, widespread mental health problems, such as debilitating depression and suicides, became more widespread several months after the event.

Research has also found that basic differences in socioeconomic status can make big differences in how likely someone is to have sustained PTSD. One study found that 9/11 survivors who earned less than $25,000 a year had a 49 percent chance of having PTSD, whereas those who made more than $100,000 per annum had only a 6 percent risk.

And not everyone who suffered from PTSD or other symptoms the event had any direct contact with the attacks—or even lived in the affected areas. One survey, published in 2002 in JAMA The Journal of the American Medical Association, found that in the month or two afterward, some 4.3 percent of the general population had signs of PTSD. The more graphic television coverage of the attacks a person had watched in the intervening time, the more likely they were to report the major symptoms.

A new kind of psychological first aid

At the time of the September 11 attacks, the accepted protocol for handling large-scale traumatic events was to perform so-called critical incident stress debriefing, like that Dass-Brailsford led in New York, to discuss events and assess how people are reacting psychologically.

In the past decade, however, research has shown that sort of intervention, no matter how well intentioned, is probably not the most helpful response to get victims feeling better more quickly. As Watson notes, these sessions might well "be too brief to allow for adequate emotional processing, may increase arousal and anxiety levels or may inadvertently decrease the likelihood that individuals will pursue more intense interventions.

Since the late 1990s, the trauma-response field has been moving toward what is known as psychological "first aid." This triage approach "is designed to reduce distress, foster short- and long-term adaptive functioning, and link survivors with additional services," Watson and her co-authors explained in a new paper, also published in the September issue of American Psychologist. Psychological first aid's focus is on practical needs so that, the theory goes, other immediate stressors, such as finding a safe place or a way to reach relatives, do not exacerbate trauma from the event itself.

In the days after the 2010 earthquake in Haiti, for example, many public health officials worried that rather than infectious diseases, mental health was going to be a more pressing issue for the country. Sandro Galea, chair of the Department of Epidemiology of Columbia's Mailman School of Public Health, noted at the time that, "psychological first aid is giving people what they need to rebuild their lives. It will mean restoring people to their jobs, restoring people to their schools, restoring families."

Current guidelines, published in 2008, suggest a five-pronged approach to promote mental and emotional well-being after a disaster or during ongoing violence: "promoting a sense of safety, promoting calming, promoting a sense of self-efficacy and community efficacy, promoting connectedness and instilling hope," Watson and her colleagues summarized in their recent paper.

Treating terrorism's psychological wounds

The study of psychological reactions to terrorism is ongoing. But in the past decade researchers have made small steps in understanding how it is similar to other traumatic events, such as experiencing natural disasters, and how it differs. "Terrorism and human-caused disasters can have strong impacts on communities because of their uncertain and long-lasting nature, resulting in long-term stress and disruption," Watson notes.

To treat victims of terrorism, mental health practitioners have been turning to cognitive behavioral therapy, which has gained favor in recent years to treat many common mental ailments, including depression and PTSD. In this sort of therapy, patients work through traumatic events in a safe, supportive setting. This allows them to "reprocess the experience to support the natural extinction of the fear, extinction of the painful memories," Neria says. Taking lessons from the extensive work done with veterans and other survivors with PTSD, researchers have found that "the content of the treatment could be different" when treating terrorist attack survivors "but the strategies and interventions are pretty similar," Neria says.

But cognitive behavioral therapy might not be a cure-all. People experience trauma reactions differently, Watson notes, so the field should not limit itself to cognitive-behavioral approaches entirely. "Interventions should seek to address the multitude of possible effects of disasters," she says.

As Neria points out, as well, "the mental health toll of disasters and terrorism is not limited to post-traumatic stress disorder." They can also trigger major depressive disorder, generalized anxiety disorder, complicated grief (recognized in the mental health world as being unusually strong and long-lasting), substance abuse and a host of other symptoms that might come and go over time.

But diagnosing these conditions and getting the right help to the right people has become much more efficient in the past decade. Researchers have learned to work through schools, workplaces and other institutions to more efficiently screen larger populations of people and address their specific needs.

The hazards of an anniversary

A decade is more than enough time for most witnesses to 9/11 to have recovered from any initial stress response. But that does not mean that the anniversary this year will be smooth sailing—at least emotionally.

A major anniversary of any difficult event—the death of a loved one or a damaging natural disaster—can be a tricky time. And the already extensive rehashing of 9/11 means that, "for many people, they begin to re-experience the reactions they would have had at that time," Dass-Brailsford says. Whether they were at the site of the attacks or not, people might have nightmares, trouble sleeping, difficulty concentrating or a general sense of irritation. These symptoms can be especially difficult because they "can creep up on you, and you will start feeling odd, and you won't know why," she notes.

But there is one event that might help those especially affected by the events of 9/11 to further ease their anxiety. "The new wrinkle this year will be that bin Laden was captured and killed," Dass-Brailsford says. "In doing trauma work, usually when the perpetrator is brought to justice it can be very healing for survivors," she explains. As when a burglar who has been on the loose is finally captured, locals fell safer

But in this instance, "that safety is very relative because we know that the organization that he belonged to didn't depend just on him," Dass-Brailsford says. Nevertheless, now that he has been dispatched, "for some people, now they can start working on healing and recovering.

Fortunately, large-scale traumatic events such as terrorist attacks are relatively rare, but that means that their effects on mental health are tricky to study systematically. And as Neria and his co-authors noted in their paper, "In the immediate aftermath of disasters, it may be both inappropriate and unethical for researchers to assess some of [the] key variables related to exposure [and] short-term outcomes."

In the meantime researchers are pressing on to better understand how major disasters play out in minds across the world. Disasters can leave a vastly different mental health footprint depending on where they happen, Watson notes. "Disasters occurring in developing countries, whether human-caused or natural, cause more numerous and severe mental consequences than do disasters in developed countries," she says.

And despite the new cautions against assuming people exposed to trauma are unable to rebound on their own, Watson says that she and peers in the field are hoping "to get the message across that people may need a little assistance to feel better or function better, without needing formal diagnosis or treatment," to help overcome the stigma that remains attached to seeking psychological help.