Trauma Lives in the Body, And the Immune System Remembers

How your body holds on to psychological wounds, and how we can help it let go

Introduction

When we think of trauma, we often imagine emotional scars - memories, flashbacks, or intense feelings. But trauma doesn’t just live in the mind. It lives in the body. It shows up in our immune cells, our stress hormones, and even the way our bodies respond to everyday life.

Over the past two decades, science has uncovered that the immune system “remembers” trauma, sometimes long after the danger is gone. This biological memory can affect how we feel, how we heal, and even how we get sick. This isn’t just a metaphor. Studies have shown that biological markers- like inflammatory cytokines or changes in blood cell ratios- can indicate this “memory.” 

For example, even simple blood tests- like the ratio between certain immune cells- have been shown to change in children and adolescents who’ve experienced trauma. A 2022 study by Amitai et al. found that certain immune changes- like shifts in immune cell ratios- are present in children and adolescents experiencing suicidal behavior, suggesting a link between inflammation and severe emotional distress (Amitai et al., 2022). These changes are linked to increased risk for mental health conditions, including depression, anxiety, and suicidality (Slavich & Irwin, 2014; Passos et al., 2015).

In fact, a growing body of research supports the theory that some forms of depression are rooted in chronic, low-grade inflammation- sharing overlapping symptoms like fatigue, poor concentration, and social withdrawal. A 2024 review by Nadler et al. in Neuroscience & Biobehavioral Reviews describes this inflammatory model as a key mechanism not only in depression but across multiple mental health conditions (Nadler et al., 2024).

Trauma Doesn’t Just Affect Feelings- It Changes Biology

Trauma, whether from war, abuse, neglect, or chronic stress, leaves a physical imprint. It rewires the immune system in ways that can linger for years.

Researchers have found that people who’ve experienced trauma often show signs of chronic inflammation. Their immune systems act as if they're under constant threat, responding too strongly to small stressors, and failing to properly regulate inflammation. At the same time, stress hormones like cortisol, which normally help calm the body, may stop working the way they should.

Blood markers such as IL-6, TNF-α, and NLR/PLR levels have all been associated with trauma exposure and emotional distress (Slavich & Irwin, 2014; Passos et al., 2015). In some clinical contexts, they are even being explored as indicators of risk for mental health challenges, including suicidality in youth.

What’s especially striking is that these biological changes can occur even in people who outwardly seem fine. The immune system, it turns out, may carry what the conscious mind tries to bury.

The Body and Brain Are Always Talking, And Trauma Disrupts the Conversation

The brain and the immune system are in constant communication. They share information through hormones, neural signals, and inflammatory molecules. When trauma enters the picture, that dialogue becomes distorted.

When the body is inflamed, it sends distress signals to the brain. This can change how key areas like the amygdala (which processes fear) and the hippocampus (which helps form memory) function. Inflammation can cause the amygdala to become hyper-reactive, leading to heightened anxiety or threat sensitivity, while the hippocampus may be disrupted, impairing memory formation and emotional regulation. Over time, this leads to emotional exhaustion, memory issues, depression, and even chronic physical illness.

Over time, this chronic feedback loop can lead to emotional exhaustion, heightened anxiety, depression, and increased vulnerability to physical illness. It’s not “just stress”, it’s a full-body alarm system that doesn’t know how to shut off.

Trauma in Childhood Leaves a Lasting Biological Mark

Some of the most powerful evidence of trauma’s reach comes from research on childhood adversity. Studies show that when children grow up in unsafe or unstable environments, their immune systems develop in a state of constant alert.

This heightened sensitivity can stay with them into adulthood. It affects how their bodies respond to stress, how well they regulate inflammation, and even how likely they are to develop chronic diseases like heart disease, diabetes, and autoimmune conditions.

In a sense, their immune systems are trained to survive a world that never felt safe. But that survival mode comes at a cost.

Inside the Brain: When the Immune System Goes Rogue

Inside the brain lives a small but powerful force: microglia, the brain’s resident immune cells. These cells help shape brain development, support learning, and respond to injury or infection.

But when trauma strikes, especially if it’s ongoing, microglia can become overactive. Instead of supporting healthy brain function, they begin to fuel inflammation, disrupt neural circuits, and even break down connections between brain cells.

This process doesn’t just change how we think or feel, it physically alters the brain’s structure. Trauma becomes embedded in the architecture of the nervous system, visible not just in behaviors but under the microscope.

So What Can We Do? Supporting Healing at the Cellular Level

Here’s the hopeful part: if trauma can shape the immune system, healing can reshape it too.

New research shows that anti-inflammatory treatments (like minocycline or omega-3s), and mind-body practices (like breathwork, movement, and vagus nerve stimulation), can help restore immune balance. Safe, predictable environments - combined with sleep, nutrition, and supportive relationships - act as biological safety signals.

What does this mean in practice? It means that when a child lashes out in class, their immune system may be reacting to a world that has never felt safe. It means that a policy designed to address mental health must also consider the biology of stress and inflammation. And it means that for a therapist, symptoms may be rooted not just in memory, but in the body’s long-running conversation with past harm. Understanding this allows us to create support systems that meet people where they are- biologically, emotionally, and socially.

This isn’t just self-care. It’s immune care.

Conclusion: A New Way to See Healing

If trauma is a wound, the immune system is part of the scar tissue- it remembers where we’ve been hurt. But memory isn’t destiny.

The body can change. And when we build environments that are safe, supportive, and predictable, the immune system can begin to let go of the alarm.

Trauma-informed care must go beyond empathy. It must also be biology-informed- grounded in the understanding that healing is not just psychological, but physiological.

This insight has real implications. For teachers, it might mean recognizing that a child's disruptive behavior could reflect an immune system stuck in survival mode. For therapists, it could mean considering inflammation as part of a person’s story- not just their emotional experience. And for policymakers, it means building systems that treat trauma as a public health issue, grounded in both psychology and biology.

When we treat trauma as both a psychological and biological condition, we begin to translate compassion into systems that actually heal.