The very public trials of the Boston Marathon bomber, Dzhokhar Tsarnaev, and the Colorado theater shooting suspect, James Holmes, put images and stories about these traumatic events once again in front of the public.

During both phases of the Boston Marathon bombing trial, testimony from survivors and first responders, as well as graphic images of the bombing, were front and center on television, the internet, and print media. And survivors of the Colorado theater shooting have vividly described in their trial testimony that night in detail and their terror and anguish seeing loved ones next to them dead or dying.

So what are the psychological and health effects of exposure to traumatic events like these?

What is trauma?

Traumatic events are those experiences that are perceived to be threats to one’s safety or stability and that cause physical, emotional and psychological stress or harm. In other words, these are events that fall outside the range of normal human experience and to which reactions vary according to the individual person.

Trauma is defined by the American Psychological Association as the psychological and emotional responses to those terrible events.

Traumatic events aren’t always violent. They can range from moving somewhere new to a mass disaster or even war.

For most people, trauma is experienced during and immediately after the event. But for many, the trauma may be relived for months or even years, as has been the case, for instance, with the aftereffects of the September 11 attacks.

Common psychological and emotional reactions to traumatic events include intense emotions, nightmares and flashbacks, eating and sleeping disturbances, panic reactions to smells or sudden noises, relationship problems, irritability and physical symptoms. While it may feel like you are going crazy, it’s important to remember that these are normal reactions to abnormal and traumatic experiences.

There is also evidence that one doesn’t have to be directly exposed to the traumatic event to be affected by it. Research has demonstrated that negative psychological and emotional effects can occur with media exposure.

For instance, millions of people watched repeated television coverage and graphic images from September 11. A 2013 study found that people who watched media reports of the attacks experienced post-traumatic stress and physical health symptoms for years afterward.

Recovery happens at a different pace for everyone. In this photo, the finish line of the Boston Marathon.Brian Snyder/Reuters

People don’t recover from trauma in the same way

As a crisis counselor after the Columbine High School shootings in April 1999, I witnessed those effects firsthand. In the hours and days after the shootings, we provided emergency crisis intervention not only to students who had been trapped in the school, but to family members, even to neighbors of the victims.

And in the following weeks and months, people who had watched the events unfold on television came in for counseling due to nightmares, elevated anxiety, depression – all attributed to the images they witnessed in the media. These included not only people who lived in the Littleton, Colorado area near the high school, but people from all over the metropolitan Denver area.

Over the next few years, I was teaching at a local university campus in Denver and had several former Columbine students in my classes. They had graduated from school, but never fully recovered from the trauma of that day. Sudden noises from the hall caused them to jump. A fire alarm set off during one class period caused some to panic, but not all.

This is also normal. Not everyone has the same reaction to trauma, or recovers in the same way, or in a set time frame. Research has shown that there is wide variability in recovery from trauma, with few indications as to who will recover relatively quickly and who will not.

A person’s coping strategies – how we deal with adverse situations – may be one of the ways people protect themselves, provided of course, that the coping behaviors themselves are positive. These can include talking to a supportive friend, joining a support group, allowing time to adjust and reestablishing routines.

Poor coping responses such as giving up, denial and avoiding talking about the event are associated with a poorer recovery from trauma. This can mean more negative symptoms such as continued depression, flashbacks, emotional numbing and difficulty with relationships.

It is not unusual for victims to find themselves eventually getting divorced after a trauma, for example, because they have become distant from or even abusive toward their spouse. If a person had a tendency toward depression or other mental health issues before the traumatic event occurred, that can have an effect on how well he or she recovers from the trauma.

A sign welcomes guests at the reopening and remembrance of the Century Aurora Theater in Aurora, Colorado January 17, 2013, where suspect James Holmes is accused of killing 12 people and wounding 70 others on July 20, 2012.RJ Sangosti/Pool/Reuters

New trauma can bring back old memories

In addition, people with histories of previous trauma such as combat veterans may be more vulnerable to the effects of new traumatic events.

In a study of military veterans affected by the Boston Marathon bombing, researchers found that many of the veterans reported flashbacks to combat experiences, elevated anxiety, psychological numbness, nightmares and heightened anger.

I have heard stories from students and therapy clients about traumatic events in the news suddenly reminding them of events that happened many years in the past.

One student, upon seeing the media coverage of the Virginia Tech shooting, told me he couldn’t understand why he was suddenly remembering the time his dog was run over by a car in front of him when he was seven. He reported that he experienced his memory of his dog’s death “like it just happened only yesterday.” These seemingly unconnected events may have been connected in his memory by the same emotional reaction to each events.

How can people cope with trauma?

What, then, can people do to alleviate the negative aftereffects of such events in order to return to their normal daily lives? The American Psychological Association recommends making connections with others, accepting change, meeting problems head on and taking care of yourself.

It’s also important to remember that one never completely forgets such events, nor do professionals suggest that is the goal of recovery. Healthy recovery involves acknowledging that the events were terrible but at the same time not allowing them to interfere with daily living. Even if, 10 years later, a sudden noise triggers momentary fear.

I encourage people to seek professional help if the effects become overwhelming. These are not only common sense recommendations; they are backed by decades of research.

Remember that recovery is not easy but it is possible, and that those emotional and psychological reactions are normal responses to abnormal situations.

Jeannie D DiClementi does not work for, consult to, own shares in or receive funding from any company or organisation that would benefit from this article, and has no relevant affiliations.