About half of U.S. teenagers have never visited doctors without a parent or guardian present, despite recommendations that such visits begin about age 13, a study led by a Chicago researcher shows.

Dr. Jon Klein wanted find whether the American Medical Association’s 1992 recommendation had any effect on teenagers taking an active role in their health care. But little has changed in 25 years.

“We really were going back to that question of has it gotten any better,” said Klein, head of pediatrics at the University of Illinois at Chicago Medical Center. “It’s still only about half who have had private one-on-ones with a clinician.”

The study — published in the Journal of Adolescent Health — surveyed adolescents and their parents, exploring at what age they think children and teenagers should begin to meet privately with doctors. He realized early on that key to a parent’s understanding of why doctors want to speak with teenagers alone is explaining that it’s so teenagers can take some ownership of their health.

“They still need their family’s involvement, but a good way of phrasing it might be, ‘When do you think your son or daughter will be ready to have some responsibility surrounding his or her medical care?’ ” Klein said. “When you put it that way, most parents are less oppositional about it because you’ve identified an opportunity for their child to grow.”

The most surprising finding for Klein was that both teenagers and parents seem open to private or semiprivate visits between doctor and teenager. They even agree as to the age this should happen, often suggesting at 16 or 18, Klein said.

Klein believes most survey respondents say 18 is the ideal age to make this shift because of the importance placed on the age in legal definitions in the U.S. But it is an arbitrary age, he said. An 18-year-old is not suddenly more mature, he said.

On the contrary, there are many reasons a doctor would want to begin discussing topics such as mental health, sexual and reproductive health and exposure to drugs, alcohol or tobacco as early as 11 or 12 years old, Klein said. “It really is about prevention,” he said.