Researchers at the University of North Carolina at Chapel Hill said punishments considered physically abusive included: beating, burning, kicking, hitting with an object somewhere other than the buttocks, or shaking a child less than 2 years old.
Also, increase in the frequency of spanking is associated with increased odds of abuse, and mothers who report spanking on the buttocks with an object, said Adam J. Zolotor, M.D., the study's lead author and an assistant professor in the department of family medicine in the UNC School of Medicine.
The study has been published on the Web site of the American Journal of Preventive Medicine.
Although some surveys show evidence of a modest decline in spanking over the last 30 years, recent surveys show that up to 90 percent of children between the ages of 3 and 5 years are spanked by their parents at least occasionally.
Zolotor and his co-authors conducted an anonymous telephone survey on parenting of a probability sample of 1,435 mothers in North Carolina and South Carolina in 2002.
Forty-five percent of the mothers reported that they or their partner had spanked their child in the previous 12 months and 25 percent reported spanking with an object on the buttocks.
Four percent reported using harsher forms of punishment that met the study's definition of physical abuse.
Statistical analyses of the survey data found that while any spanking was associated with increased risk of abuse, spanking with an object was strongly associated with abuse.
Only 2 percent of the mothers who reported no spanking reported use of physically abusive punishment. In comparison, 6 percent of mothers who reported spanking and 12 percent of mothers who reported spanking with an object also reported abusive punishment.