Robert H. Yolken, MD
Professor, Department of Pediatrics
Stanley Neurovirology Laboratory
Johns Hopkins University
School of Medicine
The brain-immune gut axis: a big new idea in neuropsychiatric disorders
Dr. Yolken is the Theodore and Vada Stanley Distinguished Professor of Pediatrics at the Johns Hopkins School of Medicine. He chairs the Stanley Division of Developmental Neurovirology, the nation’s first pediatric research center designed to investigate links between early childhood infections and severe mental illness including schizophrenia, bipolar disorder, depression, and autism. His research group is investigating whether these disorders can be associated with prior exposure to viral triggers such as herpesviruses and influenza viruses as well as eukaryotic organisms such as Candida albicans and the Toxoplasma gondii. Their research indicates that antimicrobial and anti-inflammatory medications have the potential to treat or prevent serious psychiatric disorders in some individuals. Dr. Yolken attended Harvard College and Harvard Medical School and received post-doctoral training at Cornell University and the National Institutes of Health. He has over 480 published peer-reviewed articles and numerous book chapters and presentations at scientific meeting.
Conference Lecture Summary
Serious psychiatric disorders such as schizophrenia, bipolar disorder, and major depression are causes of morbidity and mortality worldwide. The etiologies of these disorders have not been completely defined but are likely to include both genetic and environmental factors. Recent studies point to inflammation as a core process in these disorders and inflammatory changes in the brain have been associated with a range of cognitive and behavioral abnormalities. However the source of inflammation within the central nervous system for most of these disorders has not been identified.
Recently there has also been an increased understanding of the role of the gastrointestinal tract in human brain disorder . The gastrointestinal tract and the brain are linked by a series of inter-connections characterized as the brain-immune-gut axis by means of which inflammatory signals from the gastrointestinal tract are transmitted to the central nervous system. These interactions include direct connections, such as the vagus nerve, as well as chemical mediators such as cytokines and chemokines. There are a number of factors which can stimulate immune activation within the gastrointestinal tract. Among the principal mediators of gastrointestinal inflammation are the micro-organisms which inhabit the mucosal surfaces, collectively termed the microbiome. The microbiome includes bacteria, viruses, fungi, protozoa, and other organisms and is mediated both by genetic and environmental factors. A neonate’s microbiome is largely acquired from the mother around the time of birth and is stabilized during infancy and early childhood.
There are a number of environmental factors that can alter an individual’s microbiome including diet, exposure to cigarette smoke and other toxins, and medications. The microbiome can also be manipulated therapeutically by antibiotic, prebiotic, and probiotic medications all of which promote the development of some microorganisms at the expense of others. There have recently been a small number of clinical trials that have examined the effect of prebiotic or probiotic agents on the clinical course of psychiatric disorders. While the results of some of these trials are promising, there is a need for larger studies as well as for standardized preparations and dosing regimens. If properly verified, therapies directed as the gut-immune-brain axis might lead to novel approaches for the prevention and treatment
of human psychiatric disorders.