CHILD ABUSE is a serious and growing problem. Between 1972 and 1984 the number of suspected child-abuse cases reported to the authorities more than doubled, going from 610,000 to 1.5 million. Furthermore, experts say that many if not most incidents of abuse are never reported. Not to exaggerate the situation, the official figures must be appraised in view of the increasing rate of unsubstantiated reports, which climbed from 35 percent in 1975 to 65 percent in 1984. But no matter how one reads the numbers, approximately 525,000 substantiated cases annually represent a tremendous amount of human suffering.