A general model for treatment decisions. (a) A net benefit only occurs when the individual patient’s risk or disease severity is sufficiently high to be to the right of the treatment threshold, where the benefit and harm lines cross. (b) In most cases, there is no clear cut-off between recommended and not recommended treatments. For example, for a patient with both rheumatoid arthritis and heart failure, any benefit of non-steroidal anti-inflammatory drugs needs to be weighed against the higher risk of fluid retention and its effects on heart failure . (c) Some chronic diseases, in particular renal and liver failure, narrow the therapeutic window of many drugs and hence increase the likelihood of harm. (d) Chronic diseases can attenuate the relative benefit of treatment such as statin therapy in patients with chronic kidney disease receiving dialysis .