Mothers' boyfriends are responsible 23 percent of the time. While it's easy to believe SBS occurs only among the poor, the uneducated, the drug-addicted, the violently criminal, that simply isn't true. He must have been screaming nonstop from teething and the sitter couldn't stand the crying. As infancy gives way to toddlerhood, toilet training and misbehavior become the most common triggers. It may seem inconceivable that such minor transgressions could provoke someone to violence.
Many experts believe that, in most cases, no serious harm is intended.
Oftentimes, they lose control. They don't stop and think. But the violence may be all too intentional. Most shaking lasts up to 15 seconds and involves as many as 50 shakes. More alarming still, says Dr. Alexander, is the fact that most cases probably aren't isolated incidents.