Family Spillover Effects: Are Economic Evaluations Misrepresenting the Value of Healthcare Interventions to Society?

The societal impacts of health interventions are seldom incorporated into health economic evaluations, including the impact that illness can have on informal or unpaid caregivers and other family members (i.e., "family spillover effects"). Previous research has demonstrated that by excluding family spillover effects, the value of health interventions may be underestimated on average. In this commentary, we discuss how the inclusion of spillover effects influences how we value interventions and, given the extent to which caregiver/family effects are largely not captured or known, propose ways in which these data could be more systematically collected or estimated and used by researchers. These recommendations include prioritizing data collection alongside clinical trials and patient registries, engaging expert opinion panels, and developing mapping algorithms for estimating caregiver/family utility values from non-preference-based caregiver health-related quality-of-life measures and/or from patient preference-based measures.