How just one blow to the head could turn you into a lifelong criminal

Sustaining as minor head injury as a child may make you more likely to become a criminal, a study suggests.

In a study of more than 300,000 people, researchers in Denmark compared rates of minor traumatic brain injuries (TBIs) in minors under 10 to teens with criminal records. 

The team found that children who had suffered a concussion were more than 25 percent more likely to commit or be convicted for a crime by age 20.  

The researchers believe this could be due to concussions resulting in behavioral issues, antisocial behavior, and aggression, which could increase the risk of committing a criminal offense. 

The findings come as nearly four million Americans are expected to suffer a concussion every year, which causes the brain to forcibly bounce back and forth inside the skull, 

Usually caused by contact sports like football, the head injury has also been associated with an increased risk of brain disorders like Parkinson’s disease and dementia. 

In the study, published Monday in JAMA Pediatrics, researchers evaluated 343,027 Danish adults born between 1995 and 2000.

The team then looked at emergency room visits for children between birth and age 10 from the Danish National Patient Register and compared it to criminal justice records for teens and young adults ages 15 to 20. 

They noted that age 20 is the most likely age that Danish citizens are to commit a crime. 

Crimes evaluated included vandalism, violence, and assault. 

Of the participants, about 13,000 had been diagnosed with a minor TBI before age 10, 20,000 had committed a crime, and about 13,000 had been convicted. 

The team found that participants who had suffered a minor TBI during childhood were 26 percent more likely to commit a crime between ages 15 and 20, and they were 24 percent more likely to be convicted of a crime than those who didn’t suffer a concussion. 

The researchers wrote: ‘Our analysis confirmed that experiencing mTBI during childhood is positively associated with criminal charges and convictions in mid to late adolescence.’

While the researchers are largely unsure exactly what is behind the surge, they noted that it could be due to mood changes from sustaining a TBI. 

Though most concussions can lead to temporary feelings of irritability and anxiety, repeated injuries have been shown to cause lasting changes like anger, depression, and impulsivity, which could lead to poor decision making and criminal behavior. 

It could also be that children who go on to be criminals also take more risks in their childhood. 

Mild TBIs are usually caused by contact sports like football and soccer. The CDC recommends wearing protective headgear to protect against concussions. 

This is not the first study to find a link between TBI and criminal behavior. A 2018 study, for example, found that TBI was associated ‘with an earlier age of incarceration, increased risk of violence, and more convictions’ due to impulsivity and a lack of empathy. 

Additionally, a 2023 study in the journal Frontiers in Psychiatry found that mild TBI led to ‘significantly higher numbers of violent charges and violent convictions,’ particularly in males.