The Importance of Reliable Self‐Report Measures to Test PPPD Mechanisms

We thank Gao et al. for their thoughtful commentary 1. We share their view that advancing psychometrically informed care for persistent postural-perceptual dizziness (PPPD) requires longitudinal and mechanistic designs supported by precise self-report instruments. We affirm our mediation result as hypothesis-generating. Perceived injustice may serve as an accessible marker of psychological processes influencing functional symptom severity in PPPD. As Gao et al. 1 note, our mediation analysis between PPPD and healthy controls was cross-sectional and should be interpreted cautiously. Future studies should establish temporal precedence through prospective designs such as latent-growth or cross-lagged panel models and apply penalised regression with bootstrap optimism correction to reduce overfitting. Within this framework, perceived injustice, capturing unfairness, invalidation and loss of agency, remains a plausible indicator of cognitive-affective mechanisms that may identify patients less responsive to standard care. Testing such mechanisms requires reliable self-report instruments. A coordinated effort is needed to refine and isolate constructs in PPPD. Gao et al. 1 correctly highlight the absence of measurement-invariance testing. We add that reliance on simple composite scoring also constrains psychometric precision. Although our study did not examine item loadings directly, prior validations of the Dizziness Handicap Inventory (DHI) report inconsistent factor structures and subscale performance, suggesting that the equal-loading assumption may not be met. Despite being the most widely used measure in clinical vestibular research 2, the DHI shows variable content validity and subscale definitions 3 and was excluded from our analyses due to unacceptable variance-inflation factors. Poor construct reliability hinders downstream analysis and limits the accuracy of brain–behaviour models 4. These psychometric constraints impede mechanistic testing in PPPD. To address this, future work should establish reliable self-report frameworks guided by international standards such as the COSMIN guidelines 5. We appreciate this exchange and support continued efforts to align measurement precision with mechanistic insight. Ariel Sereda: conceptualization, methodology, writing – review and editing, writing – original draft. Diego Kaski: writing – review and editing, supervision, conceptualization. The authors declare no conflicts of interest. Data sharing is not applicable to this article as no datasets were generated or analysed during the current study.