(CNN) - As North Korea and the United States continue to rattle their nuclear sabers, public tension is rising. North Korea's claim that the missile it fired Wednesday is capable of reaching any city on the US mainland, whether true or not, adds fuel to that fear.
"All it takes is to turn on television or talk radio to be bombarded with what feels like a constant diatribe, not between the two nations but at each other," said Harvard instructor Suzet McKinney, an expert in public health preparedness and emergency response. "People are very concerned, and I worry some of our most vulnerable may begin to have difficulty in coping with that level of fear."
A CNN poll in October found that 86% of Americans believe North Korea poses a serious threat to the US, with 62% calling the rogue nation a "very serious" threat, matching the highest levels in CNN polls dating to 2000.
"Every time North Korea tests a missile or (President) Trump releases some kind of strongly worded statement, hundreds of thousands of people will come and use Nukemap," said Alex Wellerstein, an assistant professor at Stevens Institute of Technology who created Nukemap, a "mashup" that layers nuclear weapon explosion data on top of any Google Maps location.
"Sometimes, they will see what would happen in their neighborhoods, and sometimes they come and blow up countries they are afraid of," Wellerstein said. "There's amazing, almost unlimited interest in nuclear weapons at the moment, especially by younger people, say 30ish and below, who have not grown up in the Cold War."
Psychological fallout of nuclear fear
Those who grew up during the Cold War -- the 45-year period of tension between Western and Eastern Bloc countries after World War II -- found it hard to escape the relatively constant fear of a nuclear catastrophe. It was a message driven home by frequent drills and Civil Defense films such 1951's "Duck and Cover," which encouraged schoolchildren to duck under their desks if they heard the shriek of emergency sirens.
Today, we may mock the kitschy advice, but the impact of the campaign was real.
Studies of children who grew up during that era show reactions such as concern, fear, anxiety, helplessness and a feeling of lack of power and purpose in life. "Thinking that a nuclear war will occur obviates thinking about the future," wrote Harvard child psychiatrist Dr. William Beardslee, who did some of the first research on the topic.
"I grew up thinking the Big One could come at any moment, and this country -- or fear of it, the way my country reacted to the threat -- radicalized, marginalized and alienated me in ways that still affect me," admitted chef Anthony Bourdain, host of the CNN Original Series "Parts Unknown," in his book "A Cook's Tour: In Search of the Perfect Meal."
A study of Finnish teenagers during the 1991 Persian Gulf War found that those who often worried about nuclear threats were more prone to anxiety and depression five years later.
Psychological fears also show up after radiation accidents. Reporting on the impact of the catastrophic 1986 Chernobyl nuclear disaster 20 years later, the World Health Organization found more psychological than physical fallout among the local population. "Persistent myths and misperceptions about the threat of radiation have resulted in 'paralyzing fatalism' among residents of affected areas," the report said.
Programmed for 'better safe than sorry'
"Fear of death or fear of physical injuries is common in our world, and it doesn't matter if you're in the Cold War era or living today," said Shmuel Lissek, who runs the ANGST (Anxiety Neuroscience Grounded in cross-Species Translation) lab for the University of Minnesota and studies the brain's fear circuitry. "What makes nuclear war different is that we have no control over a nuclear threat."
We're biologically biased, he explains, to respond to even low-probability threats very seriously; after all, that's how our ancestors survived to pass along their genes. He calls it the "better safe than sorry" bias, which can lead to high levels of tension and fearfulness. When that's a short-lived reaction, we're OK. But when a threat response is maintained over weeks or months, "that's unhealthy and is associated with heart problems, autoimmune problems and emotional disorders, such as anxiety."
"When there is a chronic elevation of stress, hormones can even kill brain cells, particularly in the hippocampus."
How to cope with nuclear fears
Anyone who finds themselves fixating on the fear of nuclear war should seek immediate psychological help, McKinney says. But if you find that today's nuclear tweet-fests leave you only mildly anxious, she suggests trying to calm your fears with common stress-reducing techniques.
"I have found that journaling fears and where they are coming from can help process what we are feeling and move beyond those fears," she said. "Other tools are meditation and reflective thought. And If the rhetoric that is in the news becomes too much, just turn off the TV or radio. Just tune out."
Shield children as much as possible from that rhetoric, Lissek advises.
"In the nuclear age, these threats are going to pop up again and again, and most of the time, it's not going to lead to destruction," he said. "Until we know it's a real kind of threat, we need to protect our kids from it.
"As for adult friends and family members who are anxious, I would encourage education," Lissek added. "Do your own research to analyze the veracity of the threat."
Use that information to take action, because an active, goal-oriented approach creates resilience.
"Lack of control is a major factor in anxiety," he explained. "But if the person is involved in a goal-oriented activity, it's a source of resilience. It can buffer the effects of extreme stress."
One way to do that is to educate yourself on what to do in case of a nuclear emergency.
"If people feel like there is something they can do, even if it only marginally increases their chance of survival, it allows them to put their energies into something they feel increases their control," Lissek said.
Rachel Bronson, executive director and publisher of the Bulletin of the Atomic Scientists, agrees.
Bronson and her colleagues track the daily ebb and flow of nuclear risk and climate change and use that data to set the Doomsday Clock, a measure of how close mankind is to the "midnight" of global destruction. In January, the Bulletin moved the clock up from three minutes to 2½ minutes to midnight.
"Do you shelter in place or run for the hills?" Bronson asked. "If one of the results of this moment is to help people think through what they can do to be prepared, then this could be quite beneficial."
Return of 'duck and cover'
Until North Korea develops nuclear weapons at the level of those "of the high Cold War," Nukemap's Wellerstein said, there are things you might do to prepare. "It really depends on the size of the weapon, the accuracy of the weapon, the height of detonation and where you are when it goes off," Wellerstein said.
The internet is filled with government recommendations on the topic. Ready.gov, a national public service campaign from the Department of Homeland Security, has tips in 13 languages on what to do if faced with a nuclear blast, as well as links to similar information from the Centers for Disease Control and Prevention and the Environmental Protection Agency.
The advice mirrors what was sent to residents of Guam, who are within the estimated range of North Korea's nuclear ballistic missiles.
The most prevalent message: Take cover as quickly as you can, preferably in a concrete structure or underground, and stay there until told to come out.
Critics quickly draw a comparison to the '50s-era advice of "duck and cover." McKinney says that's ill-advised.
"We laughed at 'duck and cover,' " she said, "but shielding is ducking and covering. The average person can understand the shielding benefits that brick buildings and basements can provide. The goal is to get as far away from the nuclear material as possible."
Practice makes perfect
Wellerstein suggests that people not only prepare but practice with their families, just as they would for any natural disaster that might be common where they live, such as earthquakes, tornadoes or hurricanes.
"They've done studies in Washington and New York on how many casualties would be prevented in the case of a nuclear terrorist attack," he said, "and it's tens of thousands of people who would not be injured if they followed the correct behavior."
He gives the example of a 20- to 30-kiloton nuclear weapon exploding in Times Square, about a mile from his home in New Jersey.
"What kind of things might happen?" he asked. "Your windows might break, even though the heat would not be enough to knock your entire apartment building down. You'll see a bright flash, brighter than the sun. If you were trained, you would know not to go to the window. If you were not trained, going to the window would be the first thing you'd do to find out what that flash was.
"If you get into your car and leave the region, which is what a lot of my neighbors say they'd do, you're likely to be struck in traffic," he added. "Your car offers no radioactive protection. You're now exposing yourself to levels of radiation that, at a minimum, will increase your long-term cancer risk and at a maximum might actually kill you in a few days."
If your home was relatively undamaged and you stayed put for a few days, he says, the level of radiation risk would drop significantly.
"So this is a situation where your instinctive response, getting in your car and leaving, is actually the most dangerous answer," Wellerstein said.
Putting more emphasis on training the American people, Lissek says, would also help the national civil defense response to a nuclear event, if or when the unthinkable happens.
"So if it's 'run to the shelter,' that might be OK, but anything more than that should be drilled and practiced," he explained, "because they will be so caught up in the threat that they won't remember unless they have overtrained, just like the military. Then, when they face the real threat, they can push their anxiety aside and respond from their training."
Of course, experts say the best way to cope with the fear of nuclear attack is to reduce the threat itself.
"We need to be mobilized and let political leaders know that we care about this and are watching what they are doing and saying," Bronson said. "A lot of what we talk about is terrifying, but we can take steps to move back from the edge. We've done it before, and we can do it again."