Can Childhood Infections Trigger Mental Disorders?
Abstract
Understanding the role post-infectious autoimmunity plays in a large spectrum of psychiatric symptoms could lead to new avenues for the treatment and prevention of childhood mental illness.
The latest and largest-scale study to test the pediatric autoimmune neuropsychiatric disorders associated with streptococcal infection (PANDAS) hypothesis supports the curious role of infections in the development of mental illness.
Strep infection such as strep throat or scarlet fever has been linked with obsessive-compulsive disorder (OCD) and tic disorders, a controversial concept first defined by Susan Swedo, M.D., then a pediatrician-researcher at the National Institute of Mental Health (NIMH). Dramatic symptoms appear suddenly after the infection, and may include motor or vocal tics, obsessions, compulsions, and anxiety attacks.
Sonja Orlovska, M.D., says one of the main findings from the recent Danish research study testing the PANDAS hypothesis is “the connection between somatic and mental illness.”
Almost 20 years ago, Swedo and colleagues published a study about the first PANDAS cases they identified, “Pediatric Autoimmune Neuropsychiatric Disorders Associated With Streptococcal Infections: Clinical Description of the First 50 Cases” (American Journal of Psychiatry, 1998). Since then, numerous research groups have tried to prove or disprove the hypothesis.
The 2017 Danish study, “Association of Streptococcal Throat Infection With Mental Disorders: Testing Key Aspects of the PANDAS Hypothesis in a Nationwide Study,” published online in JAMA Psychiatry May 24, shows that children with preceding strep throat infections did indeed have an elevated risk of mental disorders, particularly OCD and tic disorders. However, the study also found non-streptococcal throat infection to be associated with increased risks, though to a lesser degree. This finding may support a more recent broader concept called pediatric acute-onset neuropsychiatric syndrome (PANS).
“Our study contradicts the PANDAS hypothesis to some extent,” wrote first author and co-researcher Sonja Orlovska, M.D., affiliated with the Mental Health Centre Copenhagen and the University of Copenhagen, Denmark, in an email to Psychiatric News. “Still, the risk of OCD remained highest after a step versus non-strep throat infection, pointing to a specific association between strep infection and OCD, in line with PANDAS.”
Swedo, now director of the Pediatrics and Developmental Neuroscience Branch at NIMH, called the Danish study an important addition to the growing body of PANS/PANDAS literature. “Their finding of increased rates of any mental disorder following strep infection suggests that post-infectious autoimmunity may play a role in a large spectrum of psychiatric symptoms, which could lead to new avenues for treatment and prevention of childhood mental illness,” she said in a statement to Psychiatric News.
The Danish researchers concluded that their results may favor the essential elements of PANS, because it offers an alternative to PANDAS with wider diagnostic criteria and without the restriction of streptococcal infection.
Data Specifics From the Danish Study
This PANS/PANDAS population-based cohort study used data from 1,067,743 individuals under 18 years of age in the nationwide Danish registers between January 1, 1996, and December 31, 2013, with up to 17 years of follow-up. The Danish National Health Service Register provided information on individuals with the registration of a streptococcal test. Data analysis was conducted from January 1, 2016, to February 28, 2017.
Of the children included in the study (519,821 girls and 547,922 boys), 638,265 received a streptococcal test, 349,982 of whom had positive test results at least once.
Children with positive streptococcal test results had an increased risk of any mental disorder (n = 15,408; IRR, 1.18), particularly of OCD (n = 556; IRR, 1.51) and tic disorders (n = 993; IRR, 1.35), compared with individuals who had never been tested for streptococcal infection, according the study. Furthermore, the risk of any mental disorder and OCD was more elevated after a streptococcal throat infection than after a non-streptococcal infection.
Nonetheless, individuals with a non-streptococcal throat infection also had an increased risk of any mental disorder (n = 11,315; IRR, 1.08), OCD (n = 316; IRR, 1.28), and tic disorders (n = 662; IRR, 1.25).
The study was supported in part by grants from the Lundbeck Foundation and the Program for Clinical Research Infrastructure established by the Lundbeck Foundation and the Novo Nordisk Foundation. ■
An abstract of “Association of Streptococcal Throat Infection With Mental Disorders: Testing Key Aspects of the PANDAS Hypothesis in a Nationwide Study” can be accessed here. “Pediatric Autoimmune Neuropsychiatric Disorders Associated With Streptococcal Infections: Clinical Description of the First 50 Cases” is available here.
