Factor Analysis of the BDI-II and HAMD-21 in Patients With Irritable Bowel Syndrome

The factorial validity of the Beck Depression Inventory-II (BDI-II) and the 21-item Hamilton Depression Rating Scale (HAMD-21) in individuals with Irritable Bowel Syndrome (IBS) has not yet been investigated. This study aimed to assess the factor structure of these instruments and analyze their interrelationships within the Georgian IBS population.

Principal component analysis was performed on data from 89 IBS patients. Factors were determined using eigenvalues ≥1, with factor loadings exceeding 0.4 and oblique rotations identifying factor compositions. The Kaiser-Meyer-Olkin measure, Cronbach's alpha, Bartlett's test, communality, non-redundant residuals, and the component correlation matrix were used to assess factor validity. Intercorrelations between the scales' symptoms were also analyzed.

The mean BDI-II score was 24.31 (standard deviation (SD) = 14.93) and the mean HAMD-21 score was 17.38 (SD = 8.91). According to the cutoff criteria for both scales, the sample exhibited moderate depression. The BDI-II identified three factors, while the HAMD-21 revealed four distinct factors. Combined analysis showed that most BDI-II items and core depressive symptoms from HAMD-21 clustered into Component I. Component II included four HAMD-21 items: insomnia (delayed), agitation, somatic anxiety, and insight. Significant positive correlations between paired BDI-II and HAMD-21 symptoms were found, with a high correlation (r = 0.88, p = 0.000) between the scales, differing from previous findings.

The high correlations within components, along with low non-redundant residuals and high communality, indicate satisfactory factor validity for both the BDI-II and HAMD-21. The self-report BDI-II inventory and the HAMD-21 scale are complementary in evaluating depressive symptoms in patients with IBS.