"Don't yell" isn't just good advice for kids. Parents should heed it too, according to a new study released Wednesday.
Thirteen-year-old adolescents whose parents shouted at them suffered more symptoms of depression than their peers who were spared the discipline, the study in the journal "Child Development" found.
And instead of improving the teenagers' behavior, yelling might actually aggravate it, the researchers discovered.
"This is one of the first studies to indicate that parents' harsh verbal discipline is damaging to the developing adolescent," said Ming-Te Wang, an assistant professor of psychology in education at the University of Pittsburgh, who led the study. "The notion that harsh discipline is without consequence, once there is a strong parent-child bond -- that the adolescent will understand that, 'They're doing this because they love me' -- is misguided because parents' warmth didn't lessen the effects of harsh verbal discipline."
The study, from researchers at the University of Pittsburgh and the University of Michigan, examined the consequences of yelling or screaming at children, swearing at them and insulting them by, for example, labeling them 'dumb' or 'lazy.'
Such conduct is not unusual. Many parents shift from physical to verbal discipline when their children become adolescents, the researchers noted. Ninety percent of American parents have acknowledged shouting at children of all ages at least once, and half have admitted to swearing at their teenagers or calling them names, according to an earlier study.
Researchers looked at seventh graders who attended public school in Pennsylvania. They found 13-year-olds who were yelled at by their parents had more symptoms of depression by the time they turned 14, and seemed to have more behavioral problems such as lying to their parents, being disobedient in school, stealing or fighting compared to their peers who weren't subjected to harsh verbal discipline.
Parents' hostility appeared to increase the risk of delinquency by making the adolescents more angry, irritable and belligerent.
The effect went the other way, too: Children who had conduct problems at 13 elicited more harsh verbal discipline from their parents in the following year.
"Were we surprised by the findings? Yes and no," Wang told CBSNews.com. "Yes, because as a parent, when I yell at my kids, I wouldn't dream of physically punishing them and hurting them since it seems like most parents do yell at their kids when the kids do something wrong," he said. "But on the other hand, it's not too surprising, because adolescents are very sensitive about how people see them and judge them."
The new study looked at 967 two-parent families, about half of whom were European American, 40 percent were African American and the rest were of other ethnic backgrounds. Most of the families were middle class.
They were surveyed over a two-year period about their mental health, child-rearing practices and what kind of relationship existed between the parents and children.
Parents' behavior was measured by such questions as, "In the past year, after your child has disobeyed you or done something wrong, how often have you: a) shouted, yelled, or screamed at the child, b) swore or cursed at the child, and c) called the child dumb or lazy or some other name like that?"
The adolescents' conduct was assessed by questions such as, "In the past year, how often have you: a) been disobedient in school, b) lied to your parents, c) stolen from a store, d) been involved in a gang fight, and e) damaged public or private property for fun?"
They were also given a psychological assessment, using a tool called the Children's Depression Inventory, which asks such questions as how often they had felt worthless or sad, or wanted to cry.
According to the Mayo Clinic, symptoms of depression in teenagers include feelings of sadness and crying spells for no apparent reason; irritability, frustration or anger, even over small matters; a loss of interest in normal activities and conflict with family and friends.
Wang said parents would do better talking to their children about the consequences of misbehaving that shouting and screaming at them.
"Indeed, harsh verbal discipline appears to be detrimental in all circumstances," Wang said.