When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, sends a distress signal to the hypothalamus. This area of the brain functions like a command center, communicating with the rest of the body through the nervous system so that the person has the energy to fight or flee.

“When a circuit fires repeatedly,” Dr. Shulman says, “it’s reinforced and becomes a default setting.” Over the long term, grief can disrupt the diverse cognitive domains of memory, decision-making, visuospatial function, attention, word fluency, and the speed of information processing.

There are four types of trauma: Acute trauma develops in response to a single event (like a car accident, sexual assault, or natural disaster). Complex trauma develops in response to prolonged and repeated traumatic events (such as child abuse or neglect, domestic violence, or civil unrest). Secondary/vicarious trauma develops in response to witnessing someone else’s trauma (typical among therapists, first responders, health care providers, and so on). Generational trauma is passed down from one generation to the next, particularly when it’s experienced by a collective group (as in slavery or genocide).