The drugs affect the growing brain's signalling abilities that influence our social behaviour and the way we feel pain. It's not thought adult brains are damaged in the same way by antibiotics.
The effects have been seen in experiments on young laboratory mice, and so researchers from Oxford University can't be sure the drugs would cause the same problems in small children.
Other researchers have seen that germ-free animals and those treated with antibiotics have social behavioural problems, and the Oxford team has discovered the processes that are going on.
Antibiotics disrupt the brain's microbiome, and specifically the signalling pathways that control social behaviour, said lead researcher Katerina Johnson. The young brain that is still developing is especially vulnerable to the drug.
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