The American Academy of Pediatrics put out a policy statement on the adverse outcomes associated with corporal punishment, citing FFCWS research showing a correlation between spanking and higher levels of aggression and externalizing behavior. See below for the abstract and link to the full paper.
Pediatricians are a source of advice for parents and guardians concerning the management of child behavior, including discipline strategies that are used to teach appropriate behavior and protect their children and others from the adverse effects of challenging behavior. Aversive disciplinary strategies, including all forms of corporal punishment and yelling at or shaming children, are minimally effective in the short-term and not effective in the long-term. With new evidence, researchers link corporal punishment to an increased risk of negative behavioral, cognitive, psychosocial, and emotional outcomes for children. In this Policy Statement, the American Academy of Pediatrics provides guidance for pediatricians and other child health care providers on educating parents about positive and effective parenting strategies of discipline for children at each stage of development as well as references to educational materials. This statement supports the need for adults to avoid physical punishment and verbal abuse of children.