BOSTON – Kaitlyn Greeley burst into tears when a car backfired the other day. She’s afraid to take her usual train to her job at a Boston hospital, walking or taking cabs instead. She can’t sleep.

“I know this is how people live every day in other countries. But I’m not used to it here,” said Greeley, 27, a technician at Tufts Medical Center who was on duty Monday when part of the hospital was briefly evacuated even as victims of the the Boston Marathon bombings were being treated in the emergency room.

Anger, crying jags and nightmares are all normal reactions for both survivors of the bombings and witnesses to the mayhem.

While the injured and those closest to the blasts are most prone to psychological aftershocks, even people with no physical injuries and those like Greeley might feel the emotional impact for weeks afterward as they struggle to regain a sense of security.

What’s not clear is who will suffer lingering anxiety, depression or even post-traumatic stress disorder.

But specialists say that how resilient people are helps determine how quickly they bounce back. The resilient tend to be people who share their emotions before becoming overwhelmed, who know how to cope with stress, and who have the ability to look for a silver lining — such as focusing on bystanders who helped the wounded.

Focusing on the horror, “that’s harder on our body and our mind,” said Dr. Catherine Mogil, co-director of the family trauma service at the University of California, Los Angeles. “People who tend to be able to make positive meaning out of tough situations are going to fare better.”

Among the typical reactions that psychologists say anyone who witnessed the bombings or their aftermath might experience include difficulty sleeping or eating; sweats or stomachaches; anxiety or fear — especially in crowded situations that remind people of the bombing. People may have a hard time focusing on work or other everyday activities. They may feel numb, anger easily, or cry often.

Priscilla Dass-Brailsford, a psychologist at Georgetown University Medical Center, said that if those symptoms don’t fade in about a month, of if they are bad enough to impair function, people should seek help.

For most, “time is a great healer,” said Dass-Brailsford, who served on disaster mental health teams that counseled survivors of 9/11 in New York.

Specialists say only a small number of people are expected to be so severely affected that they develop PTSD, a disorder that can include flashbacks, debilitating anxiety, irritability and insomnia months after the trauma.In Boston’s hospitals, teams of counselors and social workers are telling patients and their families what to expect in the difficult days and weeks ahead.

“Most people are having a lot of flashbacks,” and thoughts of the bombing interrupt their days and nights, said Lisa Allee, who directs the Community Violence Response Team at Boston Medical Center. “These are very typical, normal, expected emotions after any traumatic event or disaster.”

Beyond hospitalized patients, part of coping is awareness about how to take care of the psyche — turning off scary TV coverage and reading a book, going out for a quiet dinner, anything to temporarily cut the stress, says Dass-Brailsford, the disaster specialist.

That’s especially true for parents who are trying to calm their children, added UCLA’s Mogil, because kids take their emotional cues from the adults around them. .

For a lot of people, psychiatrists say, talking about their experience can be cathartic.