Factor analysis of treatment acceptability in double-blind randomised clinical trial of home-based transcranial direct current stimulation in major depression and in healthy individuals

Abstract

Background:

Treatment acceptability impacts patient preference, adherence and clinical outcomes and is recognised as important in developing new treatments.

Aims:

To evaluate factors associated with the acceptability of home-based transcranial direct current stimulation as a potential treatment for major depressive disorder (MDD).

Methods:

We conducted exploratory factor analysis using principal component analysis with varimax rotation and parallel analysis to identify underlying factors and calculated Cronbach’s alpha for both questionnaires. One questionnaire was investigated in a general population sample and another in a double-blind, randomised, sham-controlled clinical trial in MDD.

Results:

The general population cohort consisted of 879 participants (628 women), and the clinical trial cohort included 151 MDD participants (104 women). The clinical trial questionnaire was assessed at baseline and after the 10-week randomised treatment. In the general population, two factors emerged: expected benefits and safety, and potential burdens (eigenvalues 4.27 and 1.22). In the clinical trial, one factor was evident at each time point. At baseline, all items were highly correlated and loaded onto a single factor (eigenvalue 1.52, explaining 30.45% of variance). At week 10, all components except side effects loaded onto a single factor (eigenvalue 1.84, explaining 36.71%). No differences were found between active and sham treatment arms. Acceptability components were well-related: two distinct factors (expected benefits and burdens) were found in the general population, while a single factor of general acceptability was observed in the MDD cohort.

Conclusions:

These findings highlight the dynamic nature of acceptability and the importance of assessing it in treatment development.