Ecosystem Disruption, Infections, and Violence

Episode 2, part 3, with psychiatrist Robert C Bransfield, MD, examines how infections can influence neurological function and, in turn, violent behavior. Building on earlier discussions, Bransfield connects ecosystem disruptions, zoonotic disease emergence, animal models, and neurological impairment to the broader question of violence at both the individual and societal level.

Bransfield begins by emphasizing the imbalance between human technological advancement and our ability to address violence and mental health, “A serious concern is that our weapon technology is more advanced than our mental health technology, and our technology to understand violence—we need to catch up with that. We lose $20 trillion per year in the world as a result of violence.”

He warns that this imbalance raises questions, “Particularly as we're getting these weapons of mass destruction…are the people who have control of that mentally stable? Is there some way of having safeguards so that there's mental stability in the people who have control of that?”

Ecosystems, Parasites, and Emerging Infections

Bransfield then shifts to ecological disruptions and how they give pathogens a competitive advantage, “In a balanced ecosystem, there's host and there's parasites, and they're in check. But parasites, like staph or strep, reproduce every 20 minutes. Higher life forms reproduce every 20 years. So when the environment rapidly changes, parasites have a great advantage.”

These disruptions, he notes, make populations vulnerable to new diseases, “Globalization makes us exposed to different illnesses that we didn’t have resistance to. COVID-19 was a zoonotic disease—it came out of, who knows how it evolved, but it was catastrophic to millions of people.”

Animal and Human Models of Infection and Behavior

Using rabies as an example, Bransfield describes how animal models illustrate infection-behavior links, “Rabies isn’t really transmitted—it’s not a big issue with people, but it’s a good model. The animal then is more aggressive, it transmits.”

For humans, he highlights a long list of infections with neurological or behavioral implications, “There are about 20 different infections that are identified: Bartonella, Borrelia of different sorts, malaria, cerebral malaria, toxoplasmosis, herpes simplex virus. Damage to the temporal lobe can be related to diminished empathy, and that particularly has significance with violent behavior.”

From Infection to Violence: Neurological Pathways

Not all infections affect the brain in the same way, but some, Bransfield explains, can lead to behavioral change, “Some infections just cause more physical symptoms. Others may affect the brain in different ways, some of which may cause different mental impairments, but sometimes the mental impairment could be violence.”

He points to history for examples, “Encephalitis lethargica was particularly associated with violence. There were two pandemics in 1918—the Spanish flu and encephalitis lethargica. Both had some correlation with violence, but especially encephalitis lethargica.”

The neurological mechanism, he says, lies in impaired circuits that normally help us respond to danger appropriately, “In someone who has an illness, you’re fearful when there’s no danger, or you’re careless when there is danger and you’re not attentive enough to it.”

Tune into episode 1 of our series, split into 4 parts, for more background

context: Rethinking Mental Illness: The Overlooked Impact of Infection