How stress affects developing brain

By Vicky Wicks, Journal Staff Writer | Sunday, May 08, 2005

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Hormones produced under stress can have profound effects on a child's brain.

A child who is neglected, abused or exposed to violence in the home experiences stress, and stress triggers a chemical reaction in the brain, activating lower brain functions and starving higher functions.

Stress, regardless of its source, causes the adrenal glands to produce hormones, in particular, cortisol and adrenalin, Kari Scovel, a Rapid City psychologist, said. A high cortisol level modifies the developing brain, and although adults are affected by cortisol, "children are affected more profoundly," Scovel said.

Two parts of the brain - the hippocampus and the amygdala - are particularly affected by stress.

Scovel said the hippocampus is a banana-shaped part of the cortex that helps people remember. "It's the memory bank," she said, and "provides a context for holding memories ... like finding a snapshot in your brain."

The hippocampus is responsible for learning and memory and translates memories into emotion. "It's easier to remember when you have strong feelings about something," Scovel said.

In times of stress, the adrenal glands kick in and "create havoc for the hippocampus," Scovel said, which creates havoc for a child's ability to learn and remember.

The amygdala, the storehouse for emotion, interprets positively or negatively charged events. "If you're angry, the amygdala responds," she said.

Stress activates the amygdala, which becomes stronger and creates a "fight or flight" response. As a result, a child might become aggressive and defiant or become inhibited or withdrawn.

Nerve cells in the brain make connections with each other and transmit chemical signals, connecting at the synapses, where brain cells talk to one another.

Under stress, a person has fewer synaptic branches in the hippocampus. "Over time and with repeated stress, the hippocampus shrinks," Scovel said. In the developing brain, a shrunken hippocampus can result in learning disabilities.

The opposite happens in the amygdala, she said. The brain of someone who repeatedly experiences fear and trauma will have longer nerves and stronger connections in the amygdala.

The cells become stronger because the amygdala is "overworked - exhausted - it's like it kicks into overdrive," Scovel said.

And stronger connections in the amygdala result in anxiety, which comes on as a slower reaction to fear and causes stress to linger. As a result, a child experiences heightened physical responses such as sweating, increased respiration, accelerated heartbeat, and higher blood pressure.

Over time, a child can become hypervigilant, a condition characterized by worried thoughts that the world is dangerous and you need to watch your back.