Good research news is a welcome addition to the holidays. On December 6, JAMA Psychiatry published a report from Denmark showing that serious infections in childhood, especially those resulting in hospitalization, are occasionally followed by childhood psychiatric problems. Such problems include obsessive compulsive disorder, anxiety disorders, behavior disorders, schizophrenia spectrum disorders, and ADHD. Most childhood infections do no result in any such problems. Since the study followed more than one million children from birth, the results are very impressive. Such research can only be done in countries like Denmark that have national case registers covering all medical and psychiatric care for the entire population. 
The idea that an infectious agent can cause a psychiatric disorder is, of course, not entirely new. Many adult psychiatric disorders have been linked to viruses such as the herpes family and influenza, to bacteria such as that which causes syphilis, and to parasites such as Toxoplasma gondii that can cause toxoplasmosis. Regarding childhood psychiatric disorders, reports of streptococcus bacteria causing obsessive compulsive disorder and tics in children, the PANDAS syndrome, date to the late 1990s.
The main research center for research on the psychiatric aspects of infectious agents in the United States is the Stanley Medical Research Institute (SMRI) and especially the Stanley Center for Developmental Neurovirology at Johns Hopkins University Medical Center. SMRI and the Treatment Advocacy Center are associated since both were originally funded by Ted and Vada Stanley. Dr. Robert Yolken, the director of Johns Hopkins Center, is a member of the Treatment Advocacy Center's board and is also a co-author of the Danish research paper. Another co-author, Dr. Preben Mortensen, has received SMRI support for the past 20 years to pursue research along these lines.
Why is this research good news? It is good news because insofar as infectious agents are causing many childhood and adult psychiatric disorders, it opens up possible avenues for treatment with anti-infective drugs and, if effective vaccines could be found, even prevention. This contrasts with genetic theories regarding these disorders that offer little hope for treatment. It is now clear that there are hundreds of predisposing genes for most psychiatric disorders, as is true for most chronic diseases, but that the genes themselves do not cause the disorders. Rather the predisposing genes must act in combination with something else, and increasingly it is becoming clear that the something else is often an infectious agent.
This raises the obvious question of why the National Institute of Mental Health (NIMH) is studying only the genetic aspects of these disorders (to the tune of $100 million per year) and not the infectious agents. Perhaps Santa could deliver a copy of the JAMA Psychiatry article to NIMH for the holiday.
Dr. Torrey is the founder of the Treatment Advocacy Center and the Associate Director for Research of the Stanley Medical Research Institute.