Tierra Turner’s last memory of her older brother was his lifeless body under a yellow tarp behind police tape on a busy Bay Area street. She was 11–years-old. Three weeks after her brother was gunned down, Tierra started the sixth grade, carrying with her a Tinkerbell backpack and the memory of her brother and his friend’s violent deaths, according to the San Francisco Chronicle. It was a tough year. Her grades slipped and she was often in trouble for not being able to control her temper.

Fortunately for Tierra and her family, her school recognized the signs of trauma in children and entered her into a program to help her cope with her fear, anger and loss.

Most kids who suffer the aftermath of violent events do not get that kind of help. Children who do have some access to mental health assessment are often misdiagnosed as having Attention Deficit Hyperactivity Disorder — if they are diagnosed at all. Others are simply dismissed as “bad kids” or having “behavioral problems” and left to flounder inside a system that fails to treat the underlying issue.

The number of both children and adults who have not seen combat and yet are suffering the same kinds of symptoms of traumatic stress that commonly occur in combat veterans is staggering. Some 3,500 American troops were killed during the eight-year war in Iraq. The Veterans Administration estimates that following tours in Iraq, somewhere between 11 and 20 percent of servicemembers suffer from post-traumatic stress disorder (PTSD). Within that same eight-year period, 3,113 people were killed on the streets of Philadelphia. It is impossible to know how many witnesses there were to those killings, and how many people were terrified, traumatized or even physically injured in the process. Nationwide over 13,000 people were killed by guns.

One federally funded study suggests the percentage of noncombatant PTSD victims might be even higher than it is for returning soldiers. Researchers in Atlanta interviewed more than 8,000 inner-city residents, most of them African American. Two thirds of respondents said they had been violently attacked at some point in their lives. Half knew someone who had been murdered. Of the women interviewed, a third had been sexually assaulted. Roughly 30 percent of respondents had had symptoms consistent with PTSD.

Yet very few of those individuals had any access to mental health care at all, let alone specialized care for PTSD. Care was too expensive, took too much time in already stressful, busy lives, was associated with a white-dominated system that made them uncomfortable or carried a community stigma.

Even at the moment of trauma – when a person is hospitalized for an injury – there is little help available. A survey of 21 trauma centers in the nation’s most violent cities found that only three—in New Orleans, Detroit and Richmond—routinely screened victims of violence for PTSD. Trauma surgeons reported that they knew it was a problem but lacked the resources to deal with it.

Ultimately, the toxic stress that many experience in childhood leads to a lifetime of mental and physical health consequences. The psycho-social effects of PTSD in adults are well documented: Depression, anxiety and difficulty in personal relationships are common. In children, the symptoms can also include hyperactivity, risky behavior poor academic performance and moving backward in social and emotional development .

PTSD has been found to have biological effects as well, causing victims actual physiological harm beyond the traditionally understood behavioral manifestations of risk-taking, smoking, drinking and violence. For example, PTSD has been linked to chronic diseases such as obesity and type 2 diabetes.

The experience of trauma is believed to cause neurochemical changes in the brain that can increase the risk of high blood pressure and heart disease. Research also shows that these neurochemical changes may relate to abnormalities in thyroid and other hormone functions, and to increased susceptibility to infections and immunologic disorders.

Finally, PTSD is shown to have a direct effect on brain function and development. Toxic stress wreaks havoc on memory and language retrieval. Certain kinds of stressors – notably child abuse – actually change the way the brain develops in a way that increases the chance of developing other mental illnesses later in life. Meanwhile hundreds of thousands of children are living in neighborhoods beset by shootings and institutional violence.

The key takeaway is that an unstable environment, or even a single traumatic event, can set a person up for a lifetime of health problems. And at present, we are subjecting American children to trauma on a mass scale while failing to provide them with the treatment they desperately need.