Understanding Treatment Effect Terminology in Pain and Symptom Management Research

Within health services and medical research, there is a wide variety of terminology related to treatment effects. Understanding differences in types of treatment effects is especially important in pain and symptom management research where nonexperimental and quasiexperimental observational data analysis is common. We use the example of a palliative care consultation team leader considering implementation of a medication reconciliation program and a care-coordination intervention reported in the literature to illustrate population-level and conditional treatment effects and to highlight the sensitivity of values of treatment effects to sample selection and treatment assignment. Our goal is to facilitate appropriate reporting and interpretation of study results and to help investigators understand what information a decision maker needs when deciding whether to implement a treatment. Greater awareness of the reasons why treatment effects may differ across studies of the same patients in the same treatment settings can help policy makers and clinicians understand to whom a study's results may be generalized.