The biology of child maltreatment

How abuse and neglect of children leave their mark on the brain.

Scientists are discovering that early experiences can have profound long-term effects on the biological systems that govern responses to stress. If these systems lack the environment required for normal development, they may fail to function as evolution designed them. Effects on the maturing brain can be subtle as well as obvious. Disturbances at a critical time early in life may exert a disproportionate influence, creating the conditions for childhood and adult depression, anxiety, and post-traumatic stress symptoms.

The body and brain adapt to acute stress — originally, a threat to survival or bodily integrity — through the activity of the hypothalamic-pituitary-adrenal (HPA) axis and the sympathetic nervous system. The hypothalamus, at the base of the brain, secretes corticotropin-releasing factor (CRF), which stimulates the pituitary gland to release adrenocorticotropic hormone (ACTH). ACTH travels to the adrenal glands and causes the release of the stress hormones cortisol and adrenaline (epinephrine), mobilizing the body and mind for fighting or fleeing. Blood pressure and blood sugar levels rise, breathing and heart rate increase, muscles tense, and we feel anger, anxiety, or fear. The system is controlled by feedback: A high level of stress hormones signals the hypothalamus to stop issuing CRF. Along with the HPA axis, the sympathetic nervous system is activated, as CRF influences circuits that use the neurotransmitters dopamine, norepinephrine, and serotonin.

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