The fictional James Bond always had a license to kill, but new research suggests the suave spy’s movies got more violent through the years.

“In fact, they got quite a bit more violent over time,” said Dr. Robert Hancox, the study’s senior author from the University of Otago in Dunedin, New Zealand.

The concern, according to Hancox and his colleagues, is that children may watch these and other popular movies, and be exposed to an increasing amount of violence.

One researcher, who was not involved with the new work, said there is clear evidence that exposure to violent content is linked to aggressive and violent behavior in children and teens.

“So when this content shows up in films kids are seeing, it can be problematic,” said Amy Bleakley, a senior research scientist at the Annenberg Public Policy Center at the University of Pennsylvania in Philadelphia.

To test whether popular movies that are accessible and marketed to children and teens are showing more violent acts, Hancox and his colleagues analyzed the Bond movie series, which includes 23 films spanning the last 50 years.

The newer Bond movies, according to the researchers, are rated PG-13, which means children and teens are not required to go to the theater with their parents.

For the new study, published in the Archives of Pediatrics & Adolescent Medicine, researchers watched each Bond movie and counted the number of violent acts, such as one character trying to shoot or punch someone else.

They found the number of violent acts shown on the screen during the first Bond film in 1962 – Dr. No – and the latest film they analyzed in 2008 – Quantum of Solace – more than doubled from 109 to 250, respectively.

The increase didn’t come from trivial violence, such as a character slapping someone else. Instead, “The change has been in the portrayal of severe violence,” said Hancox, referring to any character punching, kicking or using a weapon.