Objectives: Investment in digital interventions for mental health conditions is growing rapidly, offering the potential to elevate systems that are currently overstretched. Despite a growing literature on economic evaluation of digital mental health interventions (DMHIs), including several systematic reviews, there is no conclusive evidence regarding their cost-effectiveness. This paper reviews the methodology used to determine their cost-effectiveness and assesses whether this meets the requirements for decision-making. In doing so we consider the challenges specific to the economic evaluation of DMHIs, and identify where consensus and possible further research is warranted.
Methods: A systematic review was conducted to identify all economic evaluations of DMHIs published between 1997 and December 2018. The searches included databases of published and unpublished research, reference lists and citations of all included studies, forward citations on all identified protocols and conference abstracts, and contacting authors researchers in the field. The identified studies were critiqued against a published set of requirements for decision-making in healthcare, identifying methodological challenges and areas where consensus is required.
Results: The review identified 67 papers evaluating DMHIs. The majority of the evaluations were conducted alongside trials, failing to capture all relevant available evidence and comparators, and long-term impact of mental health disorders. The identified interventions are complex and heterogeneous. As a result, there are a number of challenges specific to their evaluation, including estimation of all costs and outcomes, conditional on analysis viewpoint, and identification of relevant comparators. A taxonomy for DMHIs may be required to inform what interventions can reasonably be pooled and compared.
Conclusions: This study represents the first attempt to understand the appropriateness of the methodologies used to evaluate the value for money of DMHIs, helping work towards consensus and methods' harmonisation on these complex interventions.