We often hear about the correlation between spanking and child behavioral problems. News sources cite studies that support this idea. Unfortunately, though, this information may be misleading. Several articles are often written from the same, small piece of research.
Having said that, there are several large studies that all say spanking causes behavioral problems.
A 1997 study by three psychiatrists surveyed 807 families over the course of two years to examine the effect of spanking on antisocial behavior specifically (such as fighting, stealing, bullying, or generally mistreating others). This longitudinal research found that the frequency of spanking had a strong positive correlation with antisocial behavior (ASB) two years later. Basically, the more often the kid was spanked, the more antisocial they were a few years down the road.
A 1998 study which also focused on ASB studied 933 mothers and children, and found that there was a strong correlation between corporal punishment and increased antisocial behavior. Corporal punishment was defined as a slapping on the rear or the back of the hand of the child in this study.
Conversely, some scholars believe this data is simply unreliable because they do not compare spanking with other punishment methods. A 2010 replication of a 1988 study which found a correlation between spanking and aggression found that, once adjusted for biases and confounding factors, the correlation was reduced to becoming statistically insignificant.
We can determine from this that although there is no solid proof that spanking will turn a kid into a heathen, the fact remains that larger studies either find a significant positive correlation between antisocial behavior and aggression or a slight (meaning statistically insignificant) correlation.