– The white casket is low enough for most of Jamyla elementary school classmates to gaze directly into the face of their friend, her eyes closed, her lashes long. An angel adorns the interior satin lid. A message beneath it reads, “You shall fly with new wings.”

The children have come to the wake to say goodbye to Jamyla, a fellow fourth-grader at Koch Elementary School who had been shot through a window as she completed her homework on her mother’s bed.

Destiny Sonnier, 9, cannot look at her friend’s body. “I would tell her all of my secrets and everything,” Destiny said.

Akeelah Kelly, 8, had played outside with Jamyla hours before she was killed. Now, she approaches the casket, quietly and steadfast. But when she returns home, she cries.

Jamyla had lived in a low-income Ferguson neighborhood filled with young children and endless stress — from gun violence and poverty that overwhelms their parents with debt and contributes to housing and transportation problems. Their family histories include sexual abuse, domestic violence, incarceration and foster care.

It has long been known that growing up in impoverished and dangerous neighborhoods dims life prospects. But now a commanding body of medical research presents a disturbing, biological picture of why. It suggests that the stress itself — if left unchecked — is physically toxic to child development and health.

Brain imaging, biochemical tests, genetic testing and psychiatric trials show toxic stress ravages growing children — inviting maladies such as asthma, obesity, heart disease, high blood pressure, diabetes, kidney disease and stroke in adulthood.

When children don’t get a break from the stress — when adults can’t or don’t know how to shield their children from it — their developing bodies go on a stress hormone production binge that can alter typical gene expression within their DNA. In some cases, parts of their brains are smaller and their chromosomes shorten.

Those biological and developmental changes trigger lifelong health consequences that can ultimately shorten lives.

Some pediatricians who treat children in mostly poor neighborhoods describe a toxic stress epidemic.

“I see all these beautiful babies, and I think of all the statistics, and I can calculate which of these babies is going to have problems because their home environment is so stressed that they are never going to get the right support they need to turn on those genes to get a happy involvement in life,” said Kenneth Haller, an associate professor of pediatrics at St. Louis University School of Medicine and a fellow with the American Academy of Pediatrics.

The toxic stress Haller describes isn’t limited to children of poverty. Middle-class and affluent children are not immune from the traumas of domestic violence, drug overdoses and natural disasters.

But in neighborhoods such as Jamyla’s, those stress factors are concentrated because of poverty. “We have kids who start out looking great as infants, and as they grow I can see their parents more and more distracted by all the things in their lives like food insecurity and housing insecurity,” Haller said. “And what I ultimately see is that these kids on some level start to shut down.”

Two of Jamyla’s closest friends — Akeelah and Destiny — have endured many of those struggles, both before Jamyla’s death and in the months since.

Destiny Sonnier’s fear and grief remain palpable. They linger in her own house just 300 yards down the street from Jamyla’s and in the night air that often pops with gunfire.

Two years earlier, her dad disappeared. He was found shot dead and dumped in a lot, his legs bound by zip ties.

Perhaps the most troubling research on toxic stress is how trauma experienced by adults is transferred to children.

“Akeelah says she is fine,” her mother said. “But if you knew her before this all happened, you know that she is not. As a mother, you know that she is hurting.”

Few area researchers know more about the effects of unrelenting stress on children than Washington University psychiatrist Joan Luby. For 15 years Luby has studied 90 low-income children from the St. Louis area, tracking their development through brain imaging.

Her findings suggest that children living in poverty — unless given emotional support to buffer their stress — have smaller volumes of white and gray brain matter, particularly in the critical regions of the brain known as the hippocampus and amygdala.

Luby’s research offers hope. She said children living in poverty with caregivers who are attentive to their needs are less vulnerable. Brain scans show these positive relationships can protect the brain from abnormal development.

“I think the thing that is probably most frustrating about it is that we really understand it and even know this is actually preventable,” said Luby. “So the science should be informing the public policy for prevention, but right now, it’s not.”