Shaken baby syndrome is a severe form of head injury caused by violently shaking an infant or child. It can occur from as little as 5 seconds of shaking. When an infant or toddler is shaken, the brain bounces back and forth against the skull. This can cause bruising of the brain, swelling, pressure, and bleeding in the brain. The violent shaking may result in severe injuries to the infant, permanent brain damage, or death.

Such shaking usually takes place when the infant is crying inconsolably and the frustrated caregiver loses control. In most cases, an angry parent or caregiver shakes the baby to punish or quiet the child. Many times the caregiver did not intend to harm the baby. Nevertheless, it is a form of child abuse. The result is a type of whiplash, similar to that seen in some auto accidents.

Shaken baby syndrome does not result from gentle bouncing, playful swinging or tossing the child in the air, or jogging with the child. It also is very unlikely to occur from accidents like falling off chairs or down stairs, or accidentally being dropped from a caregiver's arms. Short falls may cause other types of head injuries, although these are often minor.