Children get sick. A lot. Part of the reason children seemingly catch everything around us that’s bad is that their immune systems need to grow up, too. The immune system has to learn how to deal with the dangerous world around us with the difference being that it doesn’t care about cars or bullies getting in its way but instead about tiny pathogens like viruses and bacteria who can wrack havoc in our bodies. When immune systems grow up they invariably make mistakes or get taken by surprise on their way. Once this happens, not only do kids’ reddened little cheeks and large, watery eyes cause parents to do everything in their power to help, but infections in childhood can sometimes pose a real threat with children requiring hospitalisation and medical care. More often than not, this is just an early fright and no need for future bother once the acute infection is defeated. As it turns out, however, infections might pose long-term risks, too. Resulting from a collaboration between University of Cambridge and Karolinska Institutet, we just published a study in the journal JAMA Psychiatry, which shows that childhood infections might increase our risk for later development of severe mental illnesses such as schizophrenia. Strangely enough, the reason for infection posing such risk might be partly related to another risk factor for schizophrenia: low intelligence.