Can Childhood Infections Trigger Mental Disorders?

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.

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.

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.