The overall benefits risks and costs of multiple medical interventions may be less favourable than the sum of the benefits risks and costs of those individual interventions

Though clinical trials may give an indication as to the benefits, risks and costs of a particular intervention there may be problems applying these data to medical practice, which often consists of multiple interventions (simultaneously or serially). Mathematical analysis suggests that on account of asymmetries in the accumulation of benefits, risks and costs, clinical trials may over-estimate the benefit and under-estimate risk and cost of an individual submitting to multiple interventions. More sophisticated mathematical modelling may help correct this artefact of evidence-based medicine. (c) 2007 Published by Elsevier Ltd.