1. The factorial validity of the HAMD-21 and BDI-II in patients with IBS has not yet been explored.

2. We examined the factor structure of the HAMD-21 and BDI-II in IBS patients.

3. The factorial validity of the HAMD-21 and BDI-II in IBS patients is satisfactory.

4. The factors identified in this study are consistent with those reported in prior research.

5. Self-reports and clinician ratings are complementary rather than redundant.

Irritable Bowel Syndrome (IBS) is among the most prevalent functional gastrointestinal (GI) disorders, characterized by abdominal pain and discomfort, along with altered bowel habits, which may include predominantly diarrhea (IBS-D), constipation (IBS-C), or a combination of both (IBS-M) [1, 2, 3]. IBS impacts 5%–10% of people worldwide, with significant variations in prevalence across different countries and within various cultures [4, 5]. Recent systematic reviews and meta-analyses suggest that these variations are not due to inconsistent diagnostic criteria or methodological differences but rather reflect genuine global differences [5].

Evidence shows that IBS is associated with a poor quality of life and diminished social functioning [1]. Significant psychosocial issues, including depression, have been reported in 50%–60% of IBS patients [6, 7, 8]. The coronavirus disease 2019 (COVID-19) pandemic significantly contributed to a rise in depression, with global prevalence increasing by about 28% in 2020 [5]. IBS is also among the various GI manifestations of post-acute COVID-19 syndrome [9].

In light of the potential rise in IBS prevalence alongside the growing global burden of mental health disorders, it is crucial to address how current therapies can be adapted to manage patients with co-occurring conditions effectively. Proper identification and treatment of depression can enhance quality of life, emphasizing the need for valid depression assessment tools.

The Beck Depression Inventory (BDI), developed by Aaron T. Beck and his colleagues in 1961, quickly became a cornerstone for evaluating depression. The BDI-II used in our study is a revised version from 1966 that aligns with the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition (DSM-IV) criteria [10, 11, 12]. It includes 21 items assessing various depression symptoms, with scores ranging from 0 to 63. A total score of 0–13 typically indicates minimal depression, 14–19 suggests mild depression, 20–28 reflects moderate depression, and 29–63 signifies severe depression [10].

The Hamilton Depression Rating Scale (HAMD) is the most widely used clinician-administered assessment for depression. Developed in 1960, it provides a standardized method for diagnosing depression and monitoring changes over time. Despite Max Hamilton’s acknowledgment that there was “room for improvement” in the HAMD, the scale’s core structure has remained largely unchanged for 60 years [13]. The HAMD-21 includes 21 items assessing symptoms and functional impairments, with scores ranging from 0 to 7 indicating no depression, 8–13 suggesting mild depression, 14–18 reflecting moderate depression, and 19 or higher signifying severe depression [13].

Over the years, numerous studies have demonstrated the reliability and validity of both the BDI and the HAMD [12, 13, 14, 15]. However, none of these studies have specifically examined the factor structure of these scales within the IBS population. Factor analyses of the HAMD and BDI conducted in the general population may not be readily applicable to the IBS population due to symptom overlap between IBS and depression, as well as confounding variables such as medication use, dietary habits, comorbid conditions, and other IBS-specific factors [1].

Moreover, the majority of the evidence on IBS and co-morbid depression comes from high-income countries, particularly in Western Europe and North America, with very little clinical or academic research on the manifestations of depression in IBS patients in the South Caucasus region. Given that socio-cultural differences can affect the manifestation of mental disorders, findings from research conducted in Western countries may not be applicable.

The study aimed to examine the factor structure of two widely recognized instruments, the BDI-II and HAMD-21, and to analyze the relationships between them within the Georgian IBS population.

A prospective observational study was carried out in the Gastroenterology department of the V. Iverieli Endocrinology Metabolism Dietology Center “Enmedic”, a secondary specialist unit located in the capital city of Tbilisi (population 1,175,200). This center serves the country (population 3,716,900) by providing outpatient services. All patients aged 18 years and older with IBS who were admitted to the outpatient setting from January 1, 2020 through December 31, 2023 were eligible for participation.

A total of 287 patients suspected of having IBS were examined and 89 of these patients were selected for study participation based on a confirmed diagnosis. The diagnosis of IBS was based on the Rome IV criteria and the Bristol Stool Form Scale was used to determine the clinical form of IBS. Subjects with organic GI diseases, clinical cases with any red flag criteria, a positive Helicobacter pylori stool antigen test, or clinically significant chronic diseases (such as cardiovascular, respiratory, liver, kidney issues, or uncontrolled diabetes) were excluded. Patients were also excluded if they reported conditions that would limit the use of esophagogastroduodenoscopies, such as malignant tumors of any location, pregnancy, or lactation. Additionally, patients who had undergone any surgical operation in the past 6 months, had post-colectomy, inflammatory or obstructive bowel disease, or celiac disease were excluded. Seven patients (2.4%) opted out of participating in the study.

All patients underwent a comprehensive GI and psychological assessment. Of the 89 patients with IBS, 57 (64.04%) underwent gastroscopic examination and 32 (35.96%) underwent GI X-ray studies with barium sulfate specifically to examine the esophagus and stomach. Additionally, 44 (49.44%) patients underwent colonoscopy, which allowed us to rule out organic GI disorders. All patients were tested for Helicobacter pylori antigen in stool; all patients included in the study tested negative, which was a necessary criterion for inclusion.

Communication with the patients was conducted by the medical team. Patients were informed about the study and gave written consent to participate. The study protocol received approval from the Ethics Review Committee (N1267251.25/11/2021).

GI symptoms were assessed using the IBS symptom questionnaire, which included questions about diet, primary intestinal symptoms, defecation-related symptoms, medication intake, and extra-intestinal symptoms, as shown in Supplementary Material 1. This questionnaire was completed during a face-to-face interview.

Depression was assessed using the HAMD-21 and BDI-II. The HAMD-21, administered by trained professionals through conversation and observation, covers a range of depressive symptoms, including affective, cognitive, and somatic aspects. Item scores range from 0 to 4 (absent to severe) or from 0 to 2 (absent to clearly present).

Participants completed the self-administered BDI-II, selecting statements that best described their feelings over the past 2 weeks, including the current day. Responses were scored on a 0–3 scale, with higher scores indicating greater symptom severity. The BDI-II and HAMD-21 were both used to assess the patient’s condition for the “past week, including today”.

In the total sample of 89 patients, females comprised 59.6% (n = 53), resulting in a male-to-female ratio of 1:1.5. The age of patients ranged from 25 to 78 years, with a median age of 52 years and a mode of 38 years. The mean age was 51.4 (SD = 14.67) years. The modal age group was 25–44 years, accounting for 38 patients (42.7%), followed by the 45–64 years group, which accounted for 33 patients (37.1%).

All patients (100%) reported taking proton pump inhibitors. Fifty-two patients (58.43%) used selective histamine type 2 receptor antagonists (H2 blockers) and 82 patients (92.13%) used prokinetics. Forty-two patients (47.19%) reported taking laxatives and 21 patients (23.6%) confirmed the use of antidiarrheal medications.

Due to bothersome symptoms, 82 patients (92.13%) used analgesics/painkillers. Antidepressants were reported by 25.84% of patients and probiotics were used by 71.91% of study participants. At the time of recruitment, participants reported not having taken any medication during the previous 4 weeks. They noted the unsystematic nature of previous treatments, which were characterized by partial, low, or transitional efficacy. In some cases, patients had stopped taking medication, and for those who continued, symptoms persisted.

The GI complaint questionnaire revealed that 62 patients (69.66%) did not follow a nutritional regimen/diet and primarily ate irregularly, one to two, or three times a day. Fifty-three patients (59.55%) did not consume fiber-rich, plant-based food. Abdominal discomfort was confirmed by all patients (100%), meteorism was reported by 86 patients (96.63%), and spasmodic pain in the abdominal area at least two to three times a week was reported by 76 patients (85.39%). Pain or discomfort in the abdominal area, which improved after defecation, was experienced by 48.31% (n = 43) of patients. Twenty-four patients (26.97%) were classified as having constipation-predominant IBS (IBS-C), 19 patients (21.35%) as having diarrhea-predominant IBS (IBS-D), and 46 patients (51.69%) as having mixed IBS (IBS-M). Worsening of symptoms after meals was reported by 72 patients (80.90%). Almost all symptoms were present simultaneously in 82 patients (92.13%).

The mean BDI-II score was 24.31 (SD = 14.93), while the mean HAMD score was 17.38 (SD = 8.91). Table 1 shows that 37.1% (n = 33) of IBS patients experienced severe depression, 7.9% (n = 7) had moderate depression, and 27% (n = 24) had mild depression, resulting in an overall prevalence of 71.9% according to the BDI-II. In comparison, the HAMD results revealed that 22.5% (n = 20) of patients had mild depression, 13.5% (n = 12) had moderate depression, and 34.8% (n = 30) experienced severe depression, yielding an overall prevalence of 70.8%.

It is crucial to acknowledge that multiple IBS-related symptoms, such as fatigue, sleep disturbances, changes in appetite, physical discomfort, and concentration difficulties, significantly overlap with symptoms of depression. Therefore, there is a need for more precise and individualized approaches to managing both IBS and depression, including the selection of appropriate data collection tools.

There is an ongoing discussion about whether self-report and clinician-rated depression scales assess the same or different aspects of depression. It has been proposed that using a combination of various depression scales could capture the primary and specific domains of depression more comprehensively [16]. Accordingly, we incorporated two scales into our analyses to better understand the dimensionality of both self-reported and clinician-assessed ratings.

Self-ratings are considered to be more susceptible to bias influenced by the severity of depression. For example, individuals with severe depression may downplay their symptoms, while those with milder depression might exaggerate them [17, 18].

Furthermore, certain aspects of psychopathology, such as retardation or hypochondriasis, are challenging to assess through self-reports alone, as they are primarily observable by an external evaluator [19]. Self-rating is particularly vulnerable to fixed response biases in some individuals, such as acquiescence bias, social desirability bias, or the exaggeration of symptoms in an effort to obtain better care [17, 19]. The accuracy of self-reporting relies on the individual’s educational background and capacity for introspection, and it can be influenced by the clinician’s expectations regarding the prescribed treatment, particularly in naturalistic, non-blinded settings [19, 20]. Despite these limitations, self-reports may still capture a distinct aspect of the individual’s experience [1]. Self-rating scales provide valuable additional insights for evaluating treatment and capturing the patient’s perspective on their illness and recovery, which cannot be assessed through observer ratings alone.

The three BDI-II components identified in this study—interpreted as “cognitive distortions”, “behavioral”, and “somatic complaints”—align with those observed in previous versions of the BDI by Shafer [16], who referred to them as a “negative attitude towards self” factor, a “performance impairment” factor, and a “somatic” factor. These components are also consistent with the results reported by Hautzinger [21], which described three factors: “performance impairment”, “negative self-perception”, and “physical symptoms”, as well as with the findings of Seemüller et al. [19], who identified factors labeled “negative perception of oneself”, “performance”, and “somatic”. It is important to note that Beck’s description of the “negative attitudes towards self” factor, which includes feelings of failure, guilt, punishment, self-dislike, and worthlessness, aligns with the first component identified in our analysis [22]. However, suicidality, which may represent the most extreme manifestation of negative self-perception, did not cluster with the other “negative self-perception” components.

Numerous studies have explored the component structure of the HAMD, particularly the original 17-item version, which has been the focus of extensive research. While some evidence suggests a relatively stable factor structure, not all studies support this finding [16, 23]. In our opinion, several methodological problems may have contributed to these discrepancies. First, inadequate sample size has frequently been a significant concern, with many studies involving fewer than 100 participants—an approach that poses a high risk of yielding unstable factor solutions [22, 24]. Additionally, differences in study populations, different methods for factor extraction, diverse criteria for factor rotation, and various rotational techniques could account for the inconsistencies between studies [25].

The four-factor solution proposed by Shafer’s meta-analysis was largely supported. It identifies a “depression factor” encompassing core depressive symptoms, along with an “anxiety factor”, a “sleep factor”, and a “somatic factor” [16]. In line with prior findings, the HAMD-21 demonstrated strong internal consistency (Cronbach’s alpha = 0.90).

Considering that the HAMD-21 and the BDI-II exhibit an approximately 50% overlap in symptoms, our study did not reveal a distinct separation into two separate component groups when both instruments were used simultaneously. In our combined analyses, nearly all items from the BDI-II, along with the core depressive symptoms from the HAMD-21, were aggregated into Component I. Component II, on the other hand, comprised four HAMD items: Insomnia (delayed), Agitation, Anxiety (somatic), and Insight. Furthermore, our study demonstrated significant positive correlations between paired symptoms from the BDI-II and HAMD-21. The strong alignment between self-ratings and clinician-rated scales is evident in the correlation of 0.88 between HAMD-21 and BDI-II, which contrasts with earlier published findings [19].

We are confident that our sample, in terms of demographic and disease characteristics, closely resembles the IBS patient population typically seen in outpatient clinics. The principal component analyses of the two frequently used instruments in this sample of IBS patients revealed three components for the BDI-II and four distinct components for the HAMD-21. However, due to high correlations between variables within the components, as well as a low percentage of non-redundant residuals and high communality, the factor validity appeared to be satisfactory for both the BDI-II and HAMD-21 scales.

Our study represents the pioneering effort to identify the dimensions of the BDI-II and the HAMD-21 in Georgian adult IBS population. However, there are limitations to consider when interpreting our results. Firstly, due to the relatively small sample size and the inclusion of participants from only one geographical area, our findings should be considered preliminary and may not be fully generalizable. Additionally, as our study focused exclusively on adults (18 years and older), further research is needed to explore these dimensions in younger populations. On the positive side, the strengths of our study include its prospective design, and simultaneous application of the two most commonly used depression scales, which ensures high-quality, reliable data and reduces susceptibility to recall bias.

The components identified in this study align with those found in previous research. Incorporating both the HAMD-21 and the BDI-II in a multimethod approach can offer a more thorough evaluation of depressive symptoms for several reasons.

Both scales measure depression but from slightly different angles, which can enhance the overall understanding of an individual’s depressive symptoms. The BDI-II, completed by the individual, provides valuable insights into their personal experience of depression. This self-report measure captures nuances in their emotional state and subjective experiences, focusing on cognitive and affective symptoms such as feelings of hopelessness and worthlessness, and is sensitive to mood changes. The HAMD-21 is a clinician-administered tool, benefiting from the clinician’s expertise in interpreting symptoms and providing a professional assessment of the severity of depression. It often assesses more severe symptoms and includes items related to physical symptoms of depression, such as sleep disturbances and appetite changes.

It is important to highlight the significance of cross-verification. Discrepancies between the scales might provide additional insights into the individual’s experience or highlight areas needing further exploration. This approach enables clinicians to develop comprehensive profiles of their patient’s conditions and evaluate the effectiveness of treatments as well as their reintegration into normal social activities.

The Beck Depression Inventory and the Hamilton Depression Rating Scale are complementary rather than redundant, highlighting the importance of using multiple measures for a comprehensive assessment of depression. Comparing results from both scales can help validate findings and ensure that depressive symptoms are consistently identified.

The datasets generated during this study are available from the corresponding author upon reasonable request. All materials and reagents used in this research can be provided upon request. This study complies with ethical guidelines, and all necessary approvals for data sharing have been secured.

AB, TK, and TS conceived and designed the research study. AB provided funding and performed the research. EB and AB contributed to data collection and processing, analysis and interpretation of the data, and the writing of the manuscript. TK and TS supervised the research and critically reviewed the manuscript. All authors contributed to editorial changes in the manuscript. All authors read and approved the final manuscript. All authors have participated sufficiently in the work and agreed to be accountable for all aspects of the work.

Communication with the patients was conducted by the medical team. Patients were informed about the study and gave written consent to participate. The study protocol received approval from the Tbilisi State Medical University Ethics Review Committee (N1267251.25/11/2021). The study was conducted in accordance with the Declaration of Helsinki.

The work reported in this publication was funded by the Tbilisi State Medical University “Young Doctoral Candidates Promotion and Recruitment Program” (N0000563446(18.05.2023)).

The authors declare no conflict of interest.

Supplementary material associated with this article can be found, in the online version, at https://doi.org/10.31083/AP44020.