Difficulty is not an ethical exemption: placebo controls and epistemic responsibility in digital therapeutics

This article responds to Lutz and Ayearst’s critique of our position on placebo controls in digital therapeutics. We do not claim placebo-controlled trials are always required, nor that alternative designs are unethical. Our argument is that when observed improvements may arise from expectancy, attention, engagement, or other non-specific effects, comparator choice becomes ethically significant because it determines whether benefit can be validly attributed to the intervention itself. Placebos in clinical research contexts function as methodological instruments and their relevance extends beyond drug trials to psychotherapy and digital health interventions. Although credible sham designs in digital contexts are difficult, difficulty does not justify relaxing epistemic standards. Doing so risks permitting therapeutic claims without adequate justification and undermines transparent communication with patients and clinicians. We further reject the view that digital therapeutics are inherently low risk or that stronger evidentiary standards impede innovation. Weak standards may accelerate market entry but ultimately erode trust and obscure genuinely effective tools. Patient-centred outcomes and real-world evidence indicate whether change matters, but not what caused it. Ethical evaluation of digital therapeutics therefore requires epistemic responsibility: novelty or practical difficulty cannot justify abandoning causal attribution central to meaningful therapeutic claims.