Construct Validation of the Mind-Skin Health Index (MSHI) in Dermatology

To the Editor,

Psychodermatologic disorders are common yet frequently underrecognized in dermatology practice. Canadian dermatologists recognize psychosocial comorbidities in their patients but report barriers to systematic assessment. ¹ Epidemiologic data confirm substantial psychiatric comorbidity in dermatologic conditions, ² and global prevalence estimates underscore the scale of unmet need. ³ Despite this need, brief transdiagnostic tools designed to support psychodermatologic triage in frontline dermatology settings remain limited. ⁴

The Mind-Skin Health Index (MSHI) was developed to address this gap. Item content was informed by a systematic review of psychodermatologic assessment tools ⁴ and refined through a modified Delphi process involving 18 clinical experts across dermatology, psychiatry, psychology, and family medicine, alongside 26 patient partners with lived psychodermatologic experience. This yielded an 18-item preliminary instrument spanning 4 domains, namely, mood and anxiety symptoms, body-focused repetitive behaviors, somatosensory phenomena, and skin-related distress, each rated on a 4-point Likert scale over the past month.

To evaluate factor structure and internal consistency, we conducted exploratory factor analysis using principal axis factoring and parallel analysis in 90 dermatology outpatients at the Kaye Edmonton Clinic, Edmonton, Alberta (ethics approval: Pro00160407). Analyses were conducted using IBM SPSS Statistics (IBM Corp, Armonk, NY, USA) and jamovi (The jamovi Project, Sydney, NSW, Australia). Item-level statistics are provided in Supplementary Table 1, and the scree plot with parallel analysis is provided in Supplementary Figure 1, and the full MSHI questionnaire is included as Supplementary Figure 2.

Sampling adequacy for the preliminary instrument was strong, supporting factor analysis of the item set. As the 18-item MSHI comprised conceptually distinct domains, we compared several scored structures, including the full instrument, versions incorporating mood/anxiety screening items, and versions in which psychodermatology-specific items were retained as separate clinical flags rather than included in the composite score. This comparison showed that removing Q6 (treatment beliefs), which had low communality and poor discrimination, and Q10 (perceived severity/helplessness), which was conceptually redundant with Q13 (depression), improved model performance. The best-performing scored structure was an 11-item version comprising core skin-related distress items with integrated mood/anxiety screening items, which loaded onto a single factor representing skin-related psychosocial distress and demonstrated strong internal consistency (Cronbach’s α = .924), excellent sampling adequacy (Kaiser-Meyer-Olkin/KMO = 0.910), 55.7% explained variance, and acceptable model fit (Tucker Lewis Index/TLI = 0.915; Root Mean Square Error of Approximation/RMSEA = 0.098). The remaining 5 items, covering body-focused repetitive behaviors, somatosensory phenomena, and safety-related mental health concerns, were retained as separately reported clinical flags and not included in the composite score. This combined structure distinguishes the MSHI from dermatology quality-of-life instruments such as the Dermatology Life Quality Index, which primarily detects functional impairment attributable to skin disease, while preserving psychodermatology-specific concerns that may warrant targeted follow-up or referral.

These preliminary findings support the construct validity of the 11-item composite score as a unidimensional measure of psychosocial distress in dermatology patients. Limitations include the single-center convenience sample and absence of test–retest and convergent validity data, which will be addressed in ongoing validation. Together, these findings support the MSHI as a practical screening tool for dermatology, primary care, and integrated mental health settings.