Grownup bullies might literally have less brains

As we grow up, certainly one of the largest questions we grapple with is who we want to be. We’re not talking about career choice, but rather the type of person we hope to become.

Somewhere between 1 in 4 and 1 in 3 children has been the victim of a bully. Experimentation with different identities as we mature isn’t unusual, and most bullies eventually move on from this antisocial behavior. However, a relative few, regardless of their age, accomplishments, or power they’ve accumulated, continue to be bullies throughout adulthood.

A new study suggests why: Critical areas of grownup bullies’ brains lack the surface area and cortical thickness found in typical adult brains. Lead study author Christina Carlisi of University College London (UCL) in the UK, says:

“Our findings support the idea that, for the small proportion of individuals with life-course-persistent antisocial behaviour, there may be differences in their brain structure that make it difficult for them to develop social skills that prevent them from engaging in antisocial behaviour. These people could benefit from more support throughout their lives.”

Image source: Carlisi, et al

The study

The new study, published in Lancet Psychiatry, studied brain scans of 672 45-year-old participants. Based on reports from their families, teachers, and their own recollections, the subjects were divided into three groups:

• 441 people (66%) had no history of antisocial behavior.
• 151 people (23%) had exhibited antisocial behavior only in their adolescences.
• 80 people (12%) were lifelong bullies.

Each participant’s cerebral cortex was assessed through the measurement of the gray matter’s thickness and available cortical area as shown in MRI scans. Researchers also measured 360 different regions within the cortex.

Using the first group of people — those with no history of antisocial behavior — as a baseline, the authors of the study found that lifelong bullies had “smaller surface area and thinner cortex in brain regions associated with executive function, motivation, and affect regulation.”

Underscoring the significance of this finding is that these abnormalities were not evident in the brains of those who’d been adolescent bullies but had grown out of it. That group, however, did exhibit some puzzling reduction in surface area and thickness in “two regions in the right temporal lobe that have not been consistently implicated in previous studies of antisocial behaviour.” For bullies, though, these deficiencies appeared in a more predictable place: the “paralimbic frontal and temporal regions that have been previously implicated in antisocial behaviour.”

Image source: Carlisi, et al

Takeway: Destined to be a despot?

While this is the first study to reveal such a marked difference between the brain structures of lifelong bullies and everyone else, figuring out what to do with this information will have to wait for further research.

For one thing, says co-author UCL’s Essi Viding, “It is unclear whether these brain differences are inherited and precede antisocial behaviour, or whether they are the result of a lifetime of confounding risk factors (eg, substance abuse, low IQ, and mental health problems) and are therefore a consequence of a persistently antisocial lifestyle.”

Another co-author, Terrif Moffit of Duke University, likewise cautions against the temptation to use MRIs as a means of identifying people likely to be or become bullies, saying, “We caution against brain imaging being used for screening, as the understanding of brain structure differences are not robust enough to be applied on an individual level.”

One implication is clear: The usual punishments meted out to young bullies should be reappraised in light of their likely brain differences. On the other hand, while there appears to be more going on here neurologically than previously thought, it’s way too soon to give lifelong bullies a free pass for their antisocial behavior.