Study links infections to risk of mental health problems in children


Severe childhood infections have been linked to a later increased risk of mental disorders in a new study.

The study, published Wednesday in the journal JAMA Psychiatry, found that infections requiring hospitalizations were associated with an approximately 84% increased risk of being diagnosed with a mental disorder and an approximately 42% increased risk of to use psychotropic drugs to treat a mental disorder.

Less severe infections treated with anti-infective drugs, such as antibiotics, were associated with increased risks of 40% and 22%, respectively, according to the study.

“The surprising finding was that infections in general – and especially the less severe infections, those treated with anti-infective agents – increased the risk of the majority of mental disorders,” said Dr Ole Köhler-Forsberg. , a neuroscientist and doctoral student at Aarhus University in Denmark, who led the study.

Still, he pointed out that the study only found a correlation, so the results do not mean that infections, or receiving treatment for them, can cause mental disorders.

“Parents shouldn’t be afraid when their children get sick or when they need antibiotics,” Köhler-Forsberg said.

“Infections per se are not bad. People need infections to build up their immune system, but in some cases infection can increase the risk of mental disorders,” he said. “The overall take-home message is that there is an intimate connection between the body, the immune system, infections, inflammation and the brain.”

For the study, Köhler-Forsberg and colleagues analyzed health data from more than one million people born in Denmark between 1995 and 2012, looking closely at their medical histories from birth through their late teens. .

The data came from two registers: the Danish National Patient Register and the Danish National Prescription Register.

The researchers found associations between any infection being treated and the increased risk of later being prescribed medication for various childhood and adolescent mental disorders, with the risks differing for specific disorders.

Risks were increased for schizophrenia spectrum disorders, obsessive-compulsive disorder, personality and behavioral disorders, mental retardation, autism spectrum disorders, attention deficit hyperactivity disorder , oppositional defiant disorder/conduct disorder and tics, the researchers said.

“To our knowledge, this study is the first to indicate that any treated infection, including less severe infections, is associated with an increased risk of a wide range of mental disorders in children and adolescents,” they said. they wrote.

The study has some limitations, including that data was only analyzed up to age 18 and there was no way to confirm that patients actually had infections compared to an erroneous diagnosis.

Additionally, because the study was registry-based and observational, “we cannot conclude any causality. So it cannot be said that this infection led to this mental disorder. So we can only speculate,” said said Köhler-Forsberg.

“Our findings, at least in part, can also be explained by other things like genetics or socioeconomic status,” he said. “These are things we try to adjust to, but it’s never possible to fit everything in these studies.”

Further research is therefore needed to determine the exact mechanism behind the complex link between infections and mental disorders.

“A lot of the time, if you take someone with a mental disorder – anxiety, depression, schizophrenia – and look at their level of inflammation, it’s likely to be higher. There are probably inflammatory cytokines involved in that. disorder, and we don’t understand why,” said William Eaton, a professor of mental health at the Johns Hopkins Bloomberg School of Public Health, who was not involved in the study but conducted separate research with some authors.

Pro-inflammatory cytokines are molecules involved in the body’s inflammatory reactions. Higher levels of such molecules or some type of immune dysfunction may help explain the link between infections and mental disorders, but more research is needed.

Other hypotheses, noted in the study, include that certain infections could enter the brain and influence neurological processes or that treating infections could alter the gut microbiome – the ecosystem of bacteria and other microorganisms – and that this disturbance could have an impact on the brain.

“There are now many studies on mental disorders, inflammation and immunity,” Eaton said.

“The immune processes involved in mental disorders are terribly important because if we could understand them, we might be able to prevent or better treat the disorders – and we don’t yet have enough knowledge to do that,” said he declared.

Dr. Lena Brundin and Viviane Labrie, both researchers at Michigan’s Van Andel Research Institute, co-authored an op-ed that accompanied the new study in JAMA Psychiatry on Wednesday. They called the results “compelling”.

“The results of the Danish study leave a number of pressing questions. Because the study controlled for important confounders and validated the findings in a cohort of siblings, the findings may reflect a causal biological mechanism. What could this mechanism be? More importantly, could we reduce the incidence of debilitating childhood neuropsychiatric disorders by targeting infection? Brundin and Labrie wrote.

“Disease onset appears to occur soon after exposure, as the greatest increase in risk was observed 0-3 months post-infection,” they wrote. “These findings bring a sense of urgency to detailing the mechanisms underlying this association, particularly given the possibility that these serious and sometimes lifelong neuropsychiatric conditions may be rapidly recognized and treated with pharmacological compounds already in clinical use. ”

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