A Psychiatrist’s View on the Immune-Brain Connection
Robert C Bransfield, MD, continues to share how vector-borne infections may trigger psychiatric symptoms not through direct brain infection, but by disrupting immune signaling and gene expression.
For over five decades, psychiatrist Robert C Bransfield, MD, has treated patients with some of the most complex psychiatric conditions, many of whom failed to respond to standard therapies. Over time, a striking pattern emerged: a notable number of these patients had a history of infectious disease, particularly Lyme disease and other vector-borne infections. His observations challenge entrenched paradigms in both psychiatry and infectious disease medicine.
In the fourth part of his 4-part series, we discussed one pathogen that continues to draw attention in Bransfield’s work Bartonella. A vector-borne bacterium that has been increasingly recognized for its potential neuropsychiatric impact. “Bartonella seems to be a significant vector-borne infection,” Bransfield explains, likening it to opportunistic infections seen in immunocompromised patients, such as those with HIV. In healthy individuals, the immune system may suppress the infection. However, when another illness—like Lyme disease—disrupts immune function, latent Bartonella may emerge as a clinical problem.
While debate remains about whether Bartonella is truly tick-borne, Bransfield emphasizes its interactive nature: “You may acquire Bartonella another way, then get Lyme, and Lyme weakens the immune system, allowing Bartonella to cause symptoms it hadn’t before.”
He describes this as an example of "complex, interactive infections," where symptoms are often less about the presence of pathogens themselves and more about the immune system’s response.
Infection and the Brain: A Complex Relationship
When it comes to neurological symptoms, Bransfield says it's essential to look beyond the conventional infectious disease model. The brain, he notes, is uniquely complex, and understanding how infections influence psychiatric function involves tracking immune and gene activity over time.
In many cases, patients improve with treatment, but then relapse when medication is withdrawn. “That’s because different genes—often immune-related—upregulate or downregulate during illness and recovery,” Bransfield explains. Communication between nerve cells involves not only neurotransmitters but also “immune transmitters,” which are often overlooked but crucial in this context. This mechanism also explains why psychiatric treatments like antidepressants or mood stabilizers take weeks to show efficacy, they must influence long-term genetic and immune signaling pathways, not just brain chemistry.
Three Ways Infections Affect Brain Function
Bransfield outlines three primary ways infections can influence psychiatric symptoms:
Peripheral immune response: Infections in the body trigger immune signaling molecules that affect brain function.
Vascular effects: Some infections may damage or inflame brain blood vessels.
Direct brain infection: Though less common, some infections like neuroborreliosis (neuro-Lyme) can invade brain tissue directly.
While direct brain infections can be confirmed in autopsy studies showing Borrelia spirochetes inside neurons, Bransfield says this is relatively rare. The majority of cases involve immune signaling from the body affecting brain function.
Autoimmunity and Abrupt Neuropsychiatric Symptoms
Another serious concern is infection-triggered autoimmunity. “In some cases, there’s no adaptive immune resolution, and instead, the immune system begins attacking nerve tissue,” Bransfield explains. This is seen in conditions like PANS and PANDAS, first identified in children after strep infections but now linked to other pathogens as well.
These autoimmune reactions can lead to dramatic psychiatric symptoms, sudden-onset OCD, motor tics, aggression, confusion, or delirium. “I’ve seen patients try to jump out of windows or attack siblings,” Bransfield says. “But once treated, they can return to normal. That’s the power—and danger—of immune-driven brain disorders.”
A Call for Cross-Disciplinary Awareness
Bransfield’s work continues to bridge the gap between psychiatry and infectious disease, advocating for increased awareness of how infections and the immune system’s response to them can underlie treatment-resistant psychiatric symptoms. As the medical community continues to uncover the immune-brain connection, Bransfield’s findings highlight the need for a more integrated and nuanced approach to mental health.
Newsletter
Stay ahead of emerging infectious disease threats with expert insights and breaking research. Subscribe now to get updates delivered straight to your inbox.
