Some children control their families by the sheer power of their defiance and by humiliating, threatening and beating their parents, the Galway conference was told.
Left untreated, they go on to abuse physically their teenage dates and the abuse doubles when they marry. They then mistreat their own children, who are at risk of starting the cycle all over again.
Prof Martin Herbert of the University of Exeter painted a frightening picture for the conference of the mayhem created by children who are out of control.
Such children are most likely to come from families in which the emotional atmosphere towards them is cold, in which they see intense levels of discord or violence, in which the rules of discipline are confused and in which aggressive behaviour is not dealt with, he said.
They begin to show their "oppositional and argumentative behaviour between the ages of three and eight," he said, adding that only a minority of children showing such behaviour at an early age go on to get worse. The parents of such children tend to be "too embarrassed to admit the harassment and fear they experience daily".
"My colleagues and I have worked with very young and older children whose hostility towards their parents spilled over regularly into verbal abuse, obscenities, humiliating criticism and threats and physical assaults ranging from slaps to serious violence," he said.
Some of these children, he said, "feel omnipotent and expect everyone to respond to them accordingly". Their definite rejection of rules is "extreme and persistent".
One third of GP consultations regarding children are for behaviour problems, Dr Herbert said. Hospital, mental health services and social work services all have heavy demands made on them by children.
The approach which is most likely to succeed in dealing with such children, he said, is a collaboration between parents and professionals, where the former take an active and equal part in devising the treatment programme.