Parents, take note! Spanking your children may be harmful and could worsen their behaviour, scientists say.
"Our findings suggest that spanking is not an effective technique and actually makes children's behaviour worse not better," said lead author of the study Elizabeth T Gershoff, from the University of Texas in the US.
The study, published in the journal Psychological Science, indicates that the increase in behaviour problems cannot be attributed to various characteristics of the child, the parents, or the home environment - rather, it seems to be the specific result of spanking.
"Parents spank for many reasons, such as their educational or cultural background or how difficult their children's behaviour is," Gershoff said.
"The same reasons, which we call selection factors, can also predict children's behaviour problems, making it difficult to determine whether spanking is in fact the cause of behaviour problems," she said.
"We realised that the statistical method of propensity score matching could help us get as close to an experiment as possible," she said.
Researchers examined data from 12,112 children. When the children were five years old, their parents reported how many times they had spanked their child in the past week.
They then matched children who had been spanked with those who had not.
The results showed that children who had been spanked at age five showed greater increases in behaviour problems by age six and also by age eight when compared with children who had never been spanked.
"The fact that knowing whether a child had ever been spanked was enough to predict their levels of behaviour problems years later was a bit surprising," said Gershoff.
"It suggests that spanking at any frequency is potentially harmful to children," she added.