Somatic symptom distress and gender moderate the effect of integrative group psychotherapy for functional vertigo on vertigo handicap: A moderation analysis of a randomised controlled trial.

OBJECTIVE: Psychotherapeutic treatments for functional vertigo have shown promising results in recent years but it is still to be determined for whom these treatments work best. The aim of this study was to run a moderation analysis to identify which baseline factors may moderate the success of integrative psychotherapeutic group treatment (IPGT) as compared to a self-help group (SHG) active control.

METHODS: Data from 159 patients included in a 16-week randomised controlled trial were analysed. The outcome was vertigo-related handicap at post-treatment and gender, age, baseline somatisation, depression and anxiety were taken as putative moderators.

RESULTS: We found that baseline somatic symptoms (i.e. PHQ-15 score, p = 0.04, ∆R2 = 0.02) and gender (p = 0.04, ∆R2 = 0.02) significantly moderated the effect of treatment type on post-treatment vertigo handicap. Patients with higher PHQ-15 scores at baseline and women reduced their vertigo handicap more in IPGT as compared to in the control condition.

CONCLUSION: A possible explanation for this result is that somatic symptom distress is the central aetiopathogenetic factor of functional vertigo, while depressiveness and anxiety are rather epiphenomena in the sense of comorbidity. Although the results are not entirely consistent, according to some studies, female gender seems to be a favourable predictor of better therapy outcome. Given the high impairment and healthcare costs in those with vertigo/dizziness and psychiatric comorbidity, it is important to effectively treat these patients as early as possible. This study provides a prescriptive tool for practitioners, allowing for more patient-tailored treatment decisions.