Research into serial and mass murderers is still in its infancy, but a systemic review of the current evidence suggests that neurodevelopmental disorders might play a role.

“Research on mass and serial killing is still at a very rudimentary stage. Yet, there are suggestions that, in at least some cases, neurodevelopmental problems such as [autism spectrum disorders] or head injury may interact in a complex interplay with psychosocial factors to produce these very adverse outcomes,” a team of researchers from the United Kingdom and Sweden explained in their study, which was published in the journal Aggression and Violent Behavior.

The recent mass shooting cases of Adam Lanza, James Holmes, and Anders Brievik brought the connection between mental illness and violent crime, with an emphasis placed on autism, to the forefront of the public imagination.

Some researchers have even suggested a new diagnosis called “Criminal Autistic Psychopathy” to describe the tiny minority of autistic individuals who commit horrific crimes.

Clare S. Allely and her colleagues set out to examine the potential role of neurodevelopmental disorders, but were surprised by the “lack of rigorous research on mass and serial killers.” The researchers were able to dig up only 22 peer reviewed articles — which were all single case reports. They also included 118 web articles, 20 books, 4 book chapters, and 1 public report in their analysis.

The researchers found that more than 10 percent of serial and mass killers had ASD, and a similar proportion had a head injury.

But ASD or head injury alone cannot be blamed as the cause of these criminals’ violence. A great majority of the serial and mass murderers with these neurodevelopmental disorders also suffered significant stessors in childhood, such as the death of a close family member, a major surgery or illness, physical or sexual abuse, or parental divorce.

The findings suggest that “to a certain degree, there is a complex interplay between neurodevelopmental and environmental factors – particularly psychosocial adversity – can potentially result in an individual being predisposed to develop into a serial/mass killer,” Allely and her colleagues wrote.

The researchers used the notorious serial killer Jeffrey Dahmer as an example of how neurodevelopment disorders and psychosocial stressors could converge to produce disastrous outcomes.

Dahmer, who murdered 17 men and boys, displayed numerous indications of Asperger syndrome, Allely and her colleagues explained.

“Dahmer was also unattached during childhood and failed to bond with anyone. Further, he was known to lack reciprocal social interaction, a situation that was closely linked to his inability to make close friendships with his peers, and he was a loner as a child. His teacher noted that he was shy and rigid, unhappy, and did not make friends easily. Friends regarded him as odd and bizarre. He had difficulty with nonverbal communication, such as a dearth of facial expression, and his unusual gaze which were also consistent with nonverbal social deficits often encountered in individuals with ASD (specifically Asperger syndrome), a finding that was noted since early childhood,” they wrote.

Dahmer’s mother suffered from depression, while his father absent and inattentive. The boy who grew up to be an infamous serial killer also underwent surgery to repair a double hernia shortly before his 4th birthday, and was allegedly sexually abused by a neighbor at age 8.

“Lastly, Dahmer was greatly ambivalent about his homosexual tendency and was frustrated by it. Some believe this frustration was later channeled into sadistic behavior against people who accepted his homosexual advances,” Allely and her colleagues added.

Though the researchers found that autism might play some sort of role in serial and mass murder, they warned that the media had falsely overemphasized the link between them.

“Media reporting of violent crime committed by persons with symptoms associated with autism spectrum disorders may generate a harmful stereotype. This review highlights that although the percentage of individuals considered to have a neurodevelopmental disorder is higher than would be expected in the general population, this is nowhere near as high as indicated in the media,” the researchers said.

Allely and her colleagues noted that multiple studies had found people with ASDs were no more likely to commit violent crime than the general population — and may even be less likely.