Infectious Disease

Functional neurological disorder is real but is not caused by “toxic vaccine effects”.

April 16, 2021

3 min read

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Perez reports that he has received honoraria for continuing education lectures on functional neurological disorders and research grants from the NIH and Sidney R. Baer Jr. Foundation to study functional neurological disorders. Perez is also a founding member of the FND Society and a member of the editorial board of Epilepsy & Behavior.


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Effective communication about the possible link between functional neurological disorder and COVID-19 vaccines is “critical” to educating the public and reducing anxiety, according to a position published in JAMA Neurology.

These efforts will allow patients to make “informed decisions” about getting the COVID-19 vaccine, the researchers wrote.

“As neurologists and health professionals in the broader sense, we need to explain the nature of neurologists transparently and without judgment [functional neurological disorder], including the fact that these symptoms are real but are not the direct result of toxic vaccine effects. You can, in theory, come with a trigger like injecting saline, and these events don’t mean the current vaccines are unsafe. ” David Perez, MD, MSc, Faculty Member in the Departments of Neurology and Psychiatry and Director of the Functional Neurological Disorders Clinic at Massachusetts General Hospital, and colleagues wrote. “Furthermore, there is not just a need to educate the public about it [functional neurological disorder] (the most common neurological disorder most people have never heard of), but nocebo effects in a broader sense. “

Healio Neurology spoke to Perez to learn more about the point of view he and his colleagues have posted on JAMA Neurology.

Healio Neurology: What prompted this publication?

Perez: Our goal with this article from JAMA Neurology’s point of view was to raise awareness of the complexity of cause-effect relationships in medicine. We also wanted to raise awareness of how brain-based conditions such as functional neurological disorders can be conceptualized using the bio-psychosocial model. In the biopsychosocial model, the interaction of predisposing weak points (risk factors), acute triggers and persistent factors is considered.

Healio-Neurology: Which adverse neurological events after a COVID-19 vaccination were documented and justified?

Perez: As we noted in the article, there are a number of physical symptoms that appear after vaccination, including fever / chills, headache, fatigue, myalgia / arthralgia, lymphadenopathy, nausea, or local effects of swelling, erythema, or pain. Post-market surveillance is still extremely important for the early detection of potential adverse events. As we see with the interruption in the distribution of the Johnson & Johnson vaccine, there may also be differences between the vaccines that continue to be closely monitored by regulators.

That being said, a functional neurological disorder, a condition at the interface of neurology and psychiatry (and possibly the second most common outpatient neurological referral), can help us understand the complexities of relationships between vaccinations and post-vaccination symptoms. Both physically triggering events and emotionally charged experiences have been identified as triggering factors for the development of a functional neurological disorder. In functional neurological disorders, an important mechanism in pathophysiology is that attention to the body can induce or exacerbate symptoms.

Healio Neurology: Were there confirmed cases of functional neurological disorders in this situation?

Perez:: Generally speaking, vaccines have been described as triggers for the development of a functional neurological disorder. I expect case reports of documented functional neurological disorders after COVID-19 vaccinations will be published in the medical literature in the coming months.

Healio Neurology: How should neurologists approach these patient events while emphasizing the importance of the vaccine?

Perez:: Neurologists and neuropsychiatrists are at the forefront of diagnosing functional neurological disorders. The diagnosis of functional neurological disorder is based on signs of a physical examination and semiological features that have been shown to be specific to the disorder. It is recommended by professionals to communicate to patients the rule of signs observed on examination, in order to help the patient understand that the condition is being diagnosed on the basis of positive diagnostic findings.

Healio Neurology: Which specific educational points are important?

Perez:: For the interested reader, is a helpful website to understand the spectrum of functional neurological symptoms. There are also good educational materials available from the multidisciplinary professional Functional Neurological Disorder Society ( and patient advocacy groups such as One of the reasons we wrote this viewpoint article is to bring discussions of functional neurological disorders into mainstream medicine and public discourse. The documentary “Dis-sociated”, which is freely available on YouTube, is another educational resource that I would like to recommend to interested people to watch.

Healio Neurology: How can neurologists help their patients calm down the COVID-19 vaccine and maximize uptake?

Perez:: Transparency and open dialogue are important issues that need to be promoted. I would also like to see more awareness raising campaigns (as well as clinical and research funding) targeting functional neurological disorders. The application of the bio-psychosocial model to formulate a range of medical, neurological and psychiatric disorders will also be important to highlight the close interplay between physical and mental health.


Kim DD et al. JAMA Neurol. 2021; doi: 10.1001 / jamaneurol.2021.1042.

Martin Vargas C. separated. 2019. Available at: Accessed April 16, 2021.


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