Over the course of this multi-part series published this year, psychiatrist Robert C Bransfield, MD, has examined the intersection of infectious disease, immune dysregulation, and neuropsychiatric illness through the lens of his decades-long clinical experience treating patients with complex, treatment-resistant psychiatric symptoms. With a longstanding focus on the immune–brain interface, Bransfield has described recurring clinical patterns in which prior infectious exposures, particularly vector-borne and zoonotic infections, appear to precede persistent changes in cognition, mood, and behavior.
Across two episodes and eight published segments, the series traced how microbial exposures may influence mental health not only through direct central nervous system involvement, but through inflammatory signaling, immune-mediated gene expression changes, and disruption of neural circuits involved in emotional regulation and impulse control. Early installments focused on the clinical observation that psychiatric symptoms can emerge months to years after infections such as Lyme disease and other tick-borne illnesses, often presenting as depression, anxiety, cognitive impairment, or personality change that does not respond to standard psychiatric treatment. Bransfield emphasized that these delayed manifestations may reflect sustained immune dysregulation rather than active infection, complicating both diagnosis and management.
Subsequent discussions expanded beyond individual patients to population-level considerations. Drawing on ecological and environmental frameworks, the series explored how ecosystem disruption, zoonotic spillover, and the “microbe manipulation hypothesis” may intersect with the immune–brain axis to influence aggression, impulsivity, and social instability. Later segments examined how infection-associated inflammation may impair neural circuits involved in threat perception and behavioral inhibition, offering biologically plausible mechanisms linking infection to violent behavior—while underscoring that violence itself remains multifactorial and context dependent.
In the final installment of the series, Bransfield turns from theory to action, asking what can be done once clinicians and researchers acknowledge the links between infection, immune dysfunction, psychiatric illness, and violence.
Once that connection is recognized, he says, it opens the door to prevention. “When we have this awareness that there’s this connection between infection and mental illness, environmental changes and infection, mental illness, that sequence, and violence, it opens up a lot of opportunities for intervention to prevent that sequence from occurring.”
How Psychiatry Has Evolved And Where It Must Go Next
Bransfield situates this work within the broader evolution of psychiatric thinking. “If we look at how we’ve developed in psychiatry, 60 years ago we had what was called the DSM,” he says. “Before that, psychiatric illness was thought of as either psychoneurosis, schizophrenia, or organic brain syndrome.”
The DSM, he notes, was transformative. “This was a very revolutionary thing—to be able to break it down and categorize it—and that expanded our understanding. That’s how we move forward with scientific discoveries. We start with a simple theory, and then we expand from there.”
But simplification has limits. “We start with these fairly simplistic theories or hypotheses of what causes illness, chronic illness, mental illness, violence, and then with time, we find that they’re much more complicated,” Bransfield says. “People start being invested in their own belief system—whether mental illness is more psychological, neurological, or genetic—and we’re finding it’s a combination of many things.”
One of those components, he emphasizes, is infection. “One of those pieces is infectious disease and immune reaction from infectious disease and other triggers. A lot of times, the formula is a vulnerability combined with an environmental trigger, be it infectious disease or something else.”
What You Need to Know
Infectious disease does not explain all mental illness or violence, but it represents a modifiable contributor that may be addressed through earlier recognition, prevention, and system-level intervention.
Understanding violence as a potentially pathological process, rather than solely a moral or criminal one, opens pathways for research, including case analysis, epidemiologic studies, and biobanks similar to those used in other neurological diseases.
Progress will require collaboration across infectious disease, psychiatry, public health, and policy, supported by education, shared data systems, and a broader One Health framework that includes behavioral and mental health.
Awareness Is the First Intervention
Recognizing infection as part of this equation is not intuitive, Bransfield acknowledges. “We’re connecting things that aren’t normally connected, and that’s not an easy connection to make,” he says. “But I think that’s obvious when you look at this long enough and hard enough.”
He is careful to stress limits. “Certainly, infectious disease does not explain all mental illness, and it does not explain all violence,” he says. “But it explains a part—and it’s a part that we can potentially treat or prevent, understand, and do more with.”
Learning From Adverse Events
To move from awareness to prevention, Bransfield points to how other systems respond to catastrophic outcomes. The criminal justice system focuses on “blame, guilt, and punishment.” Civil courts emphasize “corrective action and compensation.” A no-fault model avoids assigning blame. But the most instructive approach, he argues, comes from safety investigations.
“What we do with the National Transportation Safety Board—or hospital quality assurance—is we look at what went wrong, why it went wrong, and what we can do to correct it so that it doesn’t happen again,” he says. “Then we look afterwards to see whether that correction was effective.”
Beyond individual cases, Bransfield points to population-level research. He suggests expanding this approach. “We could look at prisons and violent offenders and ask: what neurological problems are present, and what infectious diseases are more prevalent compared to the general population?” While legal and ethical barriers exist, he argues the work is necessary. “There needs to be research in that area.”
Why Biobanks and Brain Tissue Matter
Bransfield also calls for infrastructure long used in other neurological fields. “There are tissue banks and brain biobanks for neurodegenerative diseases, but they also need to be done with violence,” he says. Such data could be collected through voluntary donation, family authorization, or medical examiners. “It would be good to have that institutionalized,” he notes.
Infection, Geography, and Conflict Zones
Infections are not evenly distributed, Bransfield emphasizes. “We’d have to know what infections in what geographical area might increase the risk for violence,” he says, “just as we do with looking at what infections increase the risk for mental illness.”
Potential contributors span pathogens and systems. “It could be spirochetes, relapsing fever, different Borrelia species, Babesia, malaria, viruses, toxoplasmosis—or something we haven’t paid attention to yet,” he says.
Cluster analysis can help, but it’s complex. “There are so many variables involved,” Bransfield explains. “You’re looking at reservoirs, vectors, healthcare systems, hygiene, and environmental change—all at the same time.”
Education, Policy, and the One Health Gap
Research alone is not enough. “We need education,” Bransfield says. “We need to educate healthcare providers, policymakers, the general population—any and all stakeholders.”
Policy must follow. “We lose about $20 trillion a year globally from violence,” he notes. “Violence prevention could help prevent that, but it’s hard to make money from prevention, which makes funding challenging.”
He calls for a broader One Health framework. “One Health has to include not just veterinary, human, and environmental medicine,” Bransfield says. “It also has to include behavioral medicine, psychiatry, and mental health issues. That’s the full spectrum of One Health.”
“We’ve had great advances in weapon technology,” he says, “but we haven’t had advances in mental health technology to keep up.”
“I really believe that a lot of mental illness has an infectious disease component that may have occurred many years before,” he adds. “The infection may occur in childhood, and the manifestation may be years later. It’s hard to connect the dots—but we need to do that.”
By doing so, he argues, prevention becomes possible. “If we pull this together and work together, we can see things we never saw before,” Bransfield says. “And help prevent some of the problems that occur in the world—especially violence.” He concludes, “So let’s all work together for a healthier and safer world.”
Watch the entire series with Bransfield by going to the first episode here.
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