August 13, 2010
Posted by Thomas Insel
Hints that some mental illness may be linked to infectious agents and/or autoimmune processes date back to at least the early 20th Century. In the 21st Century, the field of microbiomics, which is mapping the microbial environment of the human organism, may transform the way we think about human physical and mental development.1 It is already clear that 90% of “our DNA” is microbial, not human. “We” are, in fact, “super-organisms” made up of thousands of species, many of which are being identified for the first time. And there are persistent individual differences in our microbial ecology established early in life.
Insights from microbiomics have proven important for understanding obesity2 and Type 1 diabetes,3 but microbiomics has not yet been a focus for research on mental illness. Yet, there are many clues linking microbiology and mental disorders, such as epidemiologic evidence of increased risk for schizophrenia associated with prenatal exposure to influenza. Probably the most compelling case for such involvement is children who develop obsessive compulsive disorder (OCD) and/or tic disorders “overnight,” following a strep infection. Despite continuing debate over its parameters, evidence is mounting in support of Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal Infections (PANDAS) — or at least a syndrome modeled on it.
Last month, the NIMH Pediatric Developmental Neuroscience Branch convened dozens of experts from the field — including prominent PANDAS critics — to update the science and attempt to achieve consensus on criteria defining the syndrome. The mere fact that the conference took place signals a change in the scientific climate. Until now, whether a child presenting with sudden onset of OCD and/or tic symptoms gets checked for possible involvement of strep has varied—often depending on which medical journals a practitioner happens to read. I am hopeful that will begin to change in light of the new evidence.
Interest in PANDAS has also been spurred by an increasingly vocal network of affected families and the clinicians who are treating their often severely-impaired children. Conference participants heard reports from the front lines by some of these clinicians, who largely corroborated key features of the syndrome, originally identified by NIMH’s Dr. Susan Swedo in the mid-l990s. These include sudden onset of mood swings, impulsivity, anxiety, impaired attention and poor handwriting in addition to obsessions, compulsions and tics. Dr. Swedo’s studies have identified