Research suggests infections may be a hidden factor in severe childhood mental illnesses

A new study in Frontiers in Child and Adolescent Psychiatry highlights the need for clinicians to consider underlying medical causes, such as infections and immune dysfunction, in severe childhood psychiatric cases, potentially transforming diagnosis and treatment approaches.

A new paper in Frontiers in Child and Adolescent Psychiatry is adding momentum to a shift in how some clinicians think about severe mental illness in children: not every case that looks psychiatric starts in the mind. The authors argue that symptoms such as anxiety, obsessive-compulsive behaviour, tics, food restriction and episodes of intense rage can, in some cases, reflect underlying medical problems including Lyme disease, Mycoplasma infection, streptococcal illness, viral exposure, inflammation or immune dysfunction.

That view is supported by a growing body of research on the links between infection and neuropsychiatric symptoms. The Centers for Disease Control and Prevention says Mycoplasma pneumoniae is a common cause of respiratory infection in children, but reviews in PubMed also note that it can produce effects outside the lungs, including neurological and psychiatric manifestations. Other studies have examined the association between microbes and disorders including autism, schizophrenia, bipolar disorder, depression and anxiety, while older work on Lyme disease and PANDAS, a condition tied to streptococcal infection, has long argued that infections can play a role in sudden-onset symptoms.

The concern raised by the new article is that a quick psychiatric label can obscure treatable causes. In practice, that can mean missed infection, immune activation, gastrointestinal problems or, in rare cases, structural brain disease. One paper discussed in the broader literature described a child whose severe obsessive-compulsive symptoms were eventually traced to a brain tumour, a reminder that similar behaviours can have very different origins. Other research has found that children with PANS and autism may also show immune and digestive abnormalities, adding to the case for a wider medical work-up when symptoms are severe or unusual.

At the same time, the evidence is not uniform. A study in JAMA Pediatrics found no significant rise in new PANDAS symptoms among children with group A streptococcal infections compared with other groups, underlining that not every infection leads to psychiatric illness. Even so, the larger message of the new review is that paediatric psychiatry may need to look beyond diagnostic labels and focus more closely on what is driving the behaviour in each individual child.