A new study out of the University of Cambridge and the University of Southampton has found solid evidence that antisocial behavior — or the lack of consideration for other people’s well-being, and a disregard for the effects of harming them — is rooted in brain structure differences. The study, published in the Journal of Child Psychology and Psychiatry, is one of the first to bring forth such clear evidence on the matter, the researchers claim.

Using magnetic resonance imaging (MRI)s, the researchers examined the brains of male adolescents and young adults who had been diagnosed with conduct disorder. Conduct disorder is something of an umbrella term for a variety of antisocial behavior problems or disorders, typically which entail some level of aggression towards people or animals, destruction of property, lying and stealing, and rule violations. There were 58 male adolescents and young adults with conduct disorder involved in the study (divided into two separate groups of those with childhood-onset conduct disorder or adolescent-onset conduct disorder), and 25 controls without the disorder. All of the participants were between 16-21 years old.

The researchers took MRIs of their brains and focused particularly on the thickness level of brain regions, comparing and contrasting them between the groups studied. When brain regions develop at a similar rate, they will usually show the same patterns of cortical thickness; so the researchers focused on thickness to determine the differences between brain development.

They found that participants who had childhood-onset conduct disorder had a higher number of correlations in thickness between brain regions, compared to those without any conduct disorder, which suggested that people with the disorder might experience disruptions in brain development throughout their childhood. Participants with adolescent-onset conduct disorder, meanwhile, actually had fewer correlations in brain thickness, hinting that there may have been disruptions in brain development during adolescence. The researchers tried to replicate the findings in another study completed at the University of Southampton, in which they analyzed 37 people with conduct disorder and compared them to 32 healthy people, and found similar results.

“There’s evidence already of differences in the brains of individuals with serious behavioral problems, but this is often simplistic and only focused on regions such as the amygdala, which we know is important for emotional behavior,” said Dr. Luca Passamonti of the Department of Clinical Neurosciences at the University of Cambridge, an author of the study, in a press release. “But conduct disorder is a complex behavioral disorder, so likewise we would expect the changes to be more complex in nature and to potentially involve other brain regions.”

Not Just Teenage Rebellion

In the past, conduct disorder was often written off as simply a form of teenage angst or rebellion. But the new study suggests that the disorder is real, embedded in brain structure from a young age.

“The differences that we see between healthy teenagers and those with both forms of conduct disorders show that most of the brain is involved, but particularly the frontal and temporal regions of the brain,” said Dr. Graeme Fairchild, associate professor in the Department of Psychology at the University of Southampton, in the press release. “This provides extremely compelling evidence that conduct disorder is a real psychiatric disorder and not, as some experts maintain, just an exaggerated form of teenage rebellion.”

Indeed, past research had investigated brain structure differences among teens with conduct disorder and healthy teens, but this is the first study to provide more clarity on the matter. The researchers still don’t fully understand why this is happening or what causes it, so they plan on continuing their research to determine whether it’s caused by a person’s genetic makeup or environment.

“There’s never been any doubt that conditions such as Alzheimer’s disease are diseases of the brain because imaging allows us to see clearly how it eats away at the brain,” Professor Nicola Toschi said in the press release, “but until now we haven’t been able to see the clear — and widespread — structural differences in the brains of youths with conduct disorder.”

Source: Fairchild G, Toschi N, Sully K, Sonuga-Barke E, Hagan C, Diciotti S. Mapping the structural organization of the brain in conduct disorder: replication of findings in two independent samples. Journal of Child Psychology and Psychiatry, 2016.