A study of routine health screening programmes found no consistent evidence that they improved health or reduced death rates and concluded that ‘while we cannot be certain that general health checks lead to benefit, we know that all medical interventions can lead to harm’. Possible harms include overtreatment due to false positive results. In routine screening for breast cancer, for example, tumours may be detected leading to major surgery when those tumours may never – if left alone – have developed into anything harmful. Furthermore, people who are better off or healthier are more likely to participate in routine screening, so the screening may not reach those who need it most. This is not to imply that the individual components of health checks are ineffective or to discount the value of targeted screening programmes in geographical areas where levels of disease are more prevalent.