Whether from long-standing cultural practices, family tradition, or a sincere belief in its effectiveness, spanking children for misbehavior is a common practice. Nearly all studies have shown it’s harmful to their long-term mental and emotional health. But some parents insist it’s sometimes necessary.

The controversy has raged for decades. Now two new studies may have finally settled the question.

The first study

One, from the University of Texas, was published last month in the journal Psychological Science. It compared the effects of spanking on more than 1,000 pairs of twins, both fraternal and identical. Researchers were trying to answer the question of whether the negative effects of corporal punishment were due to the punishment itself or to some genetic trait in the child.

Liz Gershoff, a professor of human development and family sciences at the University of Texas at Austin and the lead researcher, told The Washington Post that the results were conclusive: “There is just absolutely no evidence for a genetic component,” she said.

She added that the more children are punished physically or by verbally berating or humiliating them, the worse their behavior becomes, and the worse their mental health is affected. They also do worse in school and have lower achievement.

A second study, similar results

Harvard researchers conducted the second study, published in the journal Child Development. It reinforced earlier studies that found that corporal punishment was linked to the development of mental health issues, anxiety, depression, behavioral problems, and substance abuse disorders.

This study found that the brains of children who were spanked at home reacted to stimulation in the same way as those who had been exposed to severe forms of violence.

“Many people don’t think about spanking as a form of violence,” said senior researcher Katie A. McLaughlin in a statement. McLaughlin, director of the Stress & Development Lab in Harvard’s Department of Psychology, added that it’s a risk to children’s development.

Unfortunate irony

Gershoff told The Post that—although many parents believe corporal punishment is sometimes necessary—it actually has the opposite effect.

“And that, in turn, makes our jobs harder as parents—that’s the irony,” she said. “People are trying to improve their children’s behavior when they using physical punishment, but they’re in fact making it worse.”

For resources on helping to raise kids more effectively, check out these recommendations from the American Psychological Association (APA).