How does trauma spill from one generation to the next?

The idea that trauma can be transmitted across generations - originating with long-dead relatives and passed down to future great-grandchildren - can be a difficult concept to grasp.

But with regular news of mass shootings, covid deaths, police killings and climate disasters, a growing number of therapists and their patients, particularly among the millennial and Gen Z cohorts, are turning their attention to the far-reaching impact of trauma, past and present.

The Oscar-winning film “Everything Everywhere All at Once” and television shows such as “Transparent” have grappled with how trauma trickles down in families. Popular nonfiction books such as “What Happened to You?”, by Oprah Winfrey and Bruce Perry, have taken the concept of intergenerational trauma “from the ivory tower to the general public,” said Sandra Mattar, a clinical psychologist and specialist in trauma-informed therapy.

The medical community has taken note. In April, more than 100 psychiatrists, psychologists, medical residents and other physicians gathered virtually for a Boston Medical Center “Grand Rounds” education event focused on intergenerational trauma. Mattar, who led the session, said the high turnout reflects heightened interest in the subject.

“I believe that trauma is at the core of so many mental health problems,” said Mattar, who also is director of training at the Immigrant and Refugee Health Center at Boston Medical Center.

The good news, experts say, is just as trauma can be passed through generations, so can resilience. But tapping into that resilience often requires a deeper understanding of the original source of the trauma and the routes of transmission through families and society.

Trauma in the genes

Intergenerational trauma can stem from biology, learned behaviors and even the collective experiences of a group. Some research suggests that trauma can affect a person’s DNA and potentially influence the health of future generations far removed from the traumatic event.

Researchers have investigated whether Holocaust survivors and their children showed changes to what are known as “epigenetic markers,” chemical tags that attach to DNA and can switch genes on or off, which in turn can influence inherited traits or diseases.

These studies, led by Rachel Yehuda, director of the Center for Psychedelic Psychotherapy and Trauma Research at the Icahn School of Medicine at Mount Sinai, compared blood samples of people who experienced the horrors of the Holocaust with those of Jews living outside Europe during the war.

Through molecular analyses, researchers found an important difference: Mothers exposed to the Holocaust showed changes in the activity of a DNA segment involved in regulating the stress response. Their children, who were not directly exposed, also showed these changes.

The implications of this research are far from conclusive but suggest that the environmental wounds inflicted on one generation may be transmitted to the next. “Clearly there is a signal of something interesting happening on a molecular level with intergenerational trauma,” said Yehuda, a professor of psychiatry and neuroscience. “It will be a while before we figure it all out.”

It’s not the traumatic experience that is passed on, it’s the anxiety and world view of the survivors, said Ed Tronick, a developmental and clinical psychologist at the University of Massachusetts Chan Medical School in Worcester. Many Holocaust survivors developed a view that the world is a dangerous place where terrible things can happen anytime. Their children intuitively sensed this fear. “Children are like anxiety detectors,” Tronick said, and they pick up and adapt to these cues.

Even the great-great-grandchildren of enslaved people can experience the anxiety their parents feel about the danger of sending them out into the community. In response to parents’ behavior, a child’s “body has already begun to experience the world as dangerous, even though he doesn’t understand the dangers at that young an age,” Tronick said.

Researchers have found that a range of toxic environmental and social exposures during pregnancy, whether it’s ingesting drugs and alcohol, or the stress of living in poverty, can also be transmitted in utero.

Imprints of abuse

Studies show that an abusive childhood can profoundly affect future generations.

Researchers interviewed volunteers from the Nurses’ Health Study about the levels of abuse inflicted on them in childhood - whether they were hit with a belt, left with bruises, or sexually or verbally abused.

The imprint of this violence took a lasting toll on the women’s children, the researchers found: Depression rates were 1.7 times higher and chronic depression 2.5 times higher among the children of women who experienced severe child abuse compared with children of mothers who had not endured such abuse.

“Childhood abuse has a profound impact on adult mental health, which can then affect family members,” said Andrea Roberts, the study’s lead author and a senior research scientist at Harvard T.H. Chan School of Public Health.

Bessel van der Kolk, author of the best-selling book “The Body Keeps the Score,” characterizes trauma not merely as an event in the past, but also as something having a lasting imprint on the mind, brain and body.

In an interview, van der Kolk said intergenerational trauma can be tracked in the ways children adjust themselves to their parents’ behavior. “When your mother freezes in response to your laughing, you learn not to laugh in front of your mom,” he said.

Collective trauma

“Collective” intergenerational trauma and “racial trauma” refer to the psychological distress passed through generations as a result of historic events, including colonization, slavery and other forms of oppression.

This type of trauma reaches far beyond individuals and families and is a shared experience among a particular group, such as descendants of the 120,000 Japanese Americans and Japanese nationals who were detained in incarceration camps during World War II.

Such trauma can manifest in many ways, from heightened anxiety, depression and insomnia to other mental and emotional health problems.

Thema Bryant, a specialist on healing from trauma and president of the American Psychological Association, said many people must cope with multiple forms of trauma at the same time.

She said her own view of the world was filtered through her experience growing up in Baltimore with descendants of the transatlantic slave trade and a World War II veteran grandfather with PTSD. She’s also endured a lifetime of racism and survived sexual assault. “I’m both a survivor of trauma within my lifetime and of intergenerational trauma,” Bryant said.

In the memoir “What My Bones Know,” Stephanie Foo confronts a punishing personal history of abuse and, after being diagnosed with complex PTSD, explores how trauma can be inherited through generations.

“We are all products of our history,” she said in an email interview. “I don’t really think it’s surprising that we carry our fears, traumas, tics and insecurities and pass them on to their children to some degree, whether it’s a depression-era recipe for potato salad or a deep-seated fear of abandonment.”

Foo’s great-grandmother and grandmother survived the Japanese occupation of Malaysia during World War II and a brutal guerrilla war with Britain known as the Malayan Emergency.

“I personally believe that because my great-grandmother and grandmother had to hustle desperately to survive,” Foo said, “that has contributed to the hustle and creativity I’ve possessed in building my own career and survival skills here in America. It’s probably also contributed to my intense anxiety.”

Helping people cope with generational trauma

It often requires a holistic approach to break the grip of generational trauma, experts say.

-Awareness: Jason Wu, a Bay Area psychologist and child of refugee parents, said the first step is building awareness. A patient may have internalized the belief they’re not good enough, “but upon unpacking it, they can see how their parents’, and maybe even their parents’ parents’, constant criticisms and lack of warmth or praise is the source of this belief.”

-Mind-body therapy: Somatic, or body-based therapies such as yoga, have been found to be effective for trauma. Increasingly, expressive arts therapies employing movement, music or visual arts, are being used to help patients find more adaptive ways to cope, said Cécile Rêve, co-founder of ARTrelief, a center that provides these arts-based therapies.

-Reframing: Foo said it was important to reframe the damaging stories she’d been fed as a child. “My mother’s voice saying, ‘You’re worthless, you’re unlovable, you’re stupid,’ " she said. “I think the essence of healing has been the effort to rewrite that narrative to something more loving, forgiving and kind.”

-Breaking the cycle: Studies suggest that even children who did not experience nurturing parenting can overcome this history if, as adults, they consciously adopt positive parenting strategies with their own children.

-Activism: Directly addressing the sources of trauma, such as gun violence or racism, through activism and advocacy are also powerful tools for overcoming its grip, said Bryant, the APA president.

-Talk about it: How trauma is talked about in families can also be important. “Is it never discussed and therefore labeled as unspeakable? Or is it one part of the family’s story that is owned and claimed by each family member?” asked Arielle Scoglio, an assistant professor of health studies at Bentley University in Waltham, Mass. “The second response dispels shame related to the trauma and integrates it into a narrative that is flexible.”