Reports of child sexual abuse soared nationwide in 1984, according to a new study. "Sexual abuse reports increased an average of 35% across the country during the past 12 months," said Anne H. Cohn, executive director of the Chicago-based National Committee for the Prevention of Child Abuse, which issued the study. Child abuse reports in general, including sexual and non-sexual abuse, rose 19%, the committee said. The greatest increase in reported sexual abuse cases was in Mississippi, with 126%. Other states with increases of more than 50% were Nebraska, 121%; Missouri, 100%; Oregon, 83% and Wisconsin, 82%.