Independence Day irony: PTSD has many vets dreading, avoiding fireworks Explosive bursts somewhere in the night - somewhere close - send Marine veteran Pete Chinnici lunging to his feet and scurrying outside, heart racing, chest heaving. His instinctive mission: track, identify and "eliminate the threat." To Chinnici, 26, who served two tours in Iraq and has since dealt with a mild case of post-traumatic stress disorder, the loud, staccato pops can sound much like a machine gun. "I instantly want to know," he said, "where the sound is coming from so I can understand what I'm up against." Throughout that brief, chilling moment, Chinnici knows intellectually that he's prowling his own yard in Phoenix. Emotionally and instinctively, however, he's been momentarily yanked backward in time to an unfriendly, unpredictable, violent land. The trigger: kids playing with firecrackers. As the nation's birthday looms - and, most definitely, on July 4 - an unknown number of combat veterans, including active and retired soldiers diagnosed PTSD or not, will cringe, flinch and feel anxious as the crackle of fireworks sporadically fills their American neighborhoods, towns and cities. The annual celebration of freedom has, for many warriors, become one of the worst days of the year. Unlike some of his veteran friends who must avoid public fireworks shows, Chinnici can handle those spectacles, with a little mental effort, he said. It's the random, neighborhood bottle-rocket bangs and M-80 claps that cause him to rise to his feet in full battle mode. "Even though you're aware that it may not be anything dangerous, probably just fireworks, your body still goes through the response," said Chinnici, whose Iraqi deployments came during parts of 2005, 2006 and 2007. PTSD can carry an array of chronic, otherwise-invisible symptoms that flare momentarily or take root for a time: nervousness, hyper-emotionality, an inability to sleep, and an overreaction to seemingly humdrum, daily moments. These feelings are unleashed from deep in the memory, hardwired back to real, horrible events that occurred just once or many times during battle such as IED detonations, mortar bursts and gunfire. Visual or auditory reminders - or both - commonly set off such symptoms for veterans, said Dr. John Hart, medical science director of the Center for BrainHealth at the University of Texas at Dallas. Brendan Smialowski / AFP - Getty Images From sea to shining sea, Americans have many different ways of showing they're true to the red, white and blue. Celebrate the Fourth with this star-spangled gallery of patriotic images. Fireworks hit right in the heart of these causes. Here's an explosive-looking thing and a loud noise," said Hart, who researches the neurological components of the disorder and works with veterans whose PTSD "arousal triggers" include abrupt noises. "What they'll feel when they hear or see fireworks is mostly fear, a sense of threat as they did during combat when the IED went off or when the Humvee blew up," Hart said. Related: Thousands of veterans failing in latest battlefield -- college Many psychologists who help servicemen and women wrestling with PTSD encourage them to head to quiet places on July 4, far from fireworks displays, or to don headphones and listen to music. But even veterans or active-duty personnel who have not been diagnosed with PTSD can - and will - feel antsy when the rockets red glare burst in midair. "Firework agitation is a common reaction for those of us who've survived mortar attacks, bombings, and explosions," said Julie Weckerlein, 31, who five years ago served as a military combat correspondent for the U.S. Air Force in both Iraq and Afghanistan. She has not been diagnosed with PTSD. It wasn't until I started talking with other veterans about it that I realized that many others feel the same way I do. It's changed the way my family celebrates the July 4th holiday together, which isn't necessarily a bad thing," she added. Instead of setting off explosives or watching others do so, we find other ways - calmer, quieter ways - to celebrate our freedoms, because the holiday and this country is worthy of the celebration. For Chinnici, however, he plans to be sitting beneath a colorful, crashing fireworks display in Phoenix on July 4, watching with his kids. Dealing mentally with flash-and-boom extravaganza, he said, requires "a combination of trying to combat it from the perspective that I have my children there and I don't want them to see this PTSD-symptom scenario unfolding and, at the same time, trying to go there so that I'm fully aware of what's going on - so that I almost predict each pop." Still, he expects to shudder a bit during one showy explosive that is a favorite for most of the rest of the crowd. "The only ones that really bother me are those that veer off slightly - the whistling ones," Chinnici said. Even though you're cognitively aware of what's going on, you still look around, waiting for something to land.