How Trauma Affects the Brain and Relationships: Insights from Dan Siegel

When we go through overwhelming experiences, it is not only our emotions that are affected. Trauma shapes how our brain works, how we relate to others, and how we experience ourselves. Dan Siegel, a psychiatrist and pioneer in the field of interpersonal neurobiology, has written widely about how our brains develop in the context of relationships and how trauma can disrupt this integration.

At the heart of Siegel’s work is the idea that the mind, brain, and relationships are deeply interconnected. The brain does not grow in isolation. From birth onwards, our nervous system develops in constant interaction with caregivers and our wider environment. Safety, connection, and co-regulation support the growth of a balanced and integrated brain. In contrast, trauma and relational ruptures can disrupt these processes, leaving us less able to regulate our emotions and more vulnerable to disconnection.

Trauma and the Brain

When trauma occurs, particularly early in life, it can affect the way the different parts of the brain communicate. Siegel often describes three broad regions of the brain:

• The brainstem, which is focused on survival and basic bodily functions.

• The limbic system, which is central to emotion and memory.

• The prefrontal cortex, which helps us think clearly, make decisions, and regulate our feelings.

In moments of overwhelming stress or danger, the survival and emotional parts of the brain take charge. The prefrontal cortex becomes less accessible. This is why in trauma we may feel hijacked by panic, numbness, or reactivity. The part of the brain that normally helps us pause, reflect, and respond thoughtfully is temporarily “offline.”

Siegel has used the phrase “flipping your lid” to describe this. When we lose access to the prefrontal cortex, we cannot think our way out of distress, no matter how much we try. This explains why trauma recovery is not simply about logic or positive thinking. It is about restoring integration across the whole brain and body.

The Role of Relationships

Siegel also highlights that relationships are both the context in which trauma often occurs and the place where healing can happen. Our brains are wired for connection. The nervous system of one person can influence the nervous system of another. This is why co-regulation with a safe, attuned other is so important.

In therapy, this means that the relationship between therapist and client is not just a backdrop but part of the healing process itself. When someone feels seen, understood, and safe, new neural pathways can begin to form. Integration becomes possible where fragmentation once dominated. The therapeutic relationship offers a different experience to the relational ruptures that may have shaped the traumatic past.

Why Integration Matters

Siegel describes mental health as a state of integration. Integration is when the different parts of the brain and the different aspects of the self can work together rather than in conflict. Trauma often leads to dis-integration, where survival responses dominate, and our capacity to connect with ourselves and others is reduced.

Practices that support awareness, emotional regulation, and safe connection can all promote integration. This might include mindfulness, body-based therapies, and relational work in therapy. The key idea is that healing is not about erasing the past but about creating new connections in the brain and new possibilities in relationships.

Moving Forward

Understanding the brain in this way can help reduce shame. If trauma makes us feel reactive, numb, or cut off from others, it is not a personal failure. It reflects how our nervous system has adapted to survive. With time, patience, and safe relationships, integration can grow.

As Siegel reminds us, the mind is both within us and between us. Healing is not only about rewiring the brain but also about reconnecting with others in ways that bring safety and vitality.