Factor Structure and Validity of the Korean Version of the Patient Health Questionnaire-9 Among Early Childhood Teachers

1. INTRODUCTION

Depression is one of the most common mental health problems worldwide. Projections to 2030 have indicated that, by then, depression will be the leading cause of disease globally [1]. In South Korea (Korea), major depressive disorder constitutes a critical public health concern. In fact, various Korean populations across diverse occupations suffer depression [2-4], and compared to all other professions, teaching is identified as high-stress [5]. In particular, teachers in early childhood education are prone to stress that results in poor mental health due to the physically and emotionally demanding nature of teaching young children [6]. These teachers’ most common sources of stress include high perceived workload, time constraints, problems with child behavior, relationships with coworkers, and insufficient resources [7, 8]. Moreover, early childhood education teachers have certain additional stressors such as dealing frequently with parents and performing other non-teaching-related duties [9, 10]. Specifically in Korea, the public remains unaware of these teachers’ professionalism, so social recognition of their status is low, as are their salaries [11]. Such stressors make them more vulnerable to mental disorders, thus negatively impacting not only teachers, but also instructional quality and children’s social and emotional development [12]. Moreover, a Korean study with 1634 early childhood education teachers found that 40.6% reported mental illness such as depression [13]. Given depressive symptoms’ growing prevalence among these professional educators, accurate assessment is of great importance.

One promising depression-screening tool is the Patient Health Questionnaire-9 (PHQ-9) [14], a nine-item self-report measure based on diagnostic criteria of major depressive episodes from the Diagnostic and Statistical Manual of Mental Disorders [15]. The PHQ-9’s validity and reliability have been extensively evaluated with various populations, including psychiatric patients [16], primary care patients [14], patients with spinal cord injury [17, 18], substance abusers [19], elderly individuals [20], university students [21, 22], and adolescents [23]. As for its underlying factor structure, however, previous studies have provided mixed results. While some studies found evidence for a one-factor model reflecting the depression construct’s unidimensionality [14, 16, 19, 21-23], others supported slightly different two-factor models [17, 18, 24]. The two-factor models have in common that one factor is represented by somatic symptoms and the other by affective symptoms.

Although the PHQ-9’s psychometric properties have been examined among Korean populations, including psychiatric patients with migraine and university students [22, 25], a number of issues need further exploration. First, no consensus has been reached on the PHQ-9’s factor structure. Second, no studies have examined its factor structure with early childhood education teachers, for whom identification of this construct’s measures is especially important. Third, transferring psychometric findings among psychiatric patients with severe migraine and university students to teacher populations nurturing and instructing young children would be erroneous. Thus, this study’s purposes were: (1) to explore the PHQ-9 Korean version’s factor structure for the best data fit by employing Confirmatory Factor Analysis (CFA) to test four models suggested by the literature and (2) to assess the PHQ-9’s convergent validity with a measure reflecting a similar construct. Generally, the PHQ-9 and BDI-II are commonly used to diagnose depressive disorders and are considered reliable for measuring the severity of depressive symptoms. However, no study has examined the convergent validity of these two measures among Korean early childhood education teachers.

2. METHODS

2.3. Statistical Analysis

Statistical analysis was performed with IBM SPSS Statistics for Windows (version 23) and SPSS AMOS (version 20) (IBM Corp., Armonk, NY, USA). CFA with maximum likelihood procedure was used to assess the PHQ-9’s different latent structures. From the literature, four alternative plausible PHQ-9 models were tested. Specifically, Model 1 tested Kronke et al. [14] hypothesized original one-factor model, which posits that all items load on a single factor with uncorrelated error variance. Model 2a tested Richardson and Richard’s [18] two-factor model in which two latent variables are represented by somatic (5 items) and affective (4 items). Model 2b tested Krause et al.’s [17] two-factor model in which three items load on the somatic factor and six items on the affective factor. Finally, Model 2c, reported by Krause et al. [24], also proposed two factors, namely somatic (6 items) and affective (3 items).

Each model’s appropriateness was assessed using several fit indices, including the chi-square (χ²) and its subsequent ratio with the number of degrees of freedom (χ²/df); comparative fit index (CFI); goodness-of-fit index (GFI); root mean square error of approximation (RMSEA) and its 90% confidence interval (90% CI); and the standardized root mean square residual (SRMR). The model was considered to have good fit if the chi-square test divided by degrees of freedom is less than 3 [30], CFI ≥ 0.90 [31], GFI > 0.95 [32], RMSEA ≤ 0.06 [33], and SRMR < 0.08 [32, 33]. Chi-square difference tests were used to determine whether the models differed significantly. The PHQ-9 and BDI-II’s convergent validity was assessed using Pearson’s correlation, and the selected model’s internal consistency was calculated via Cronbach’s alpha (Fig. 1).

Table 1.

Model	k	χ²	df	χ²/df	CFI	GFI	RMSEA (90% CI)	SRMR
Model 1	9	88.0*	28	3.1	0.88	0.95	0.095 (0.073-0.117)	0.065
Model 2a	9	80.9*	27	3.0	0.90	0.95	0.092 (0.069-0.115)	0.063
Model 2b	9	44.3*	26	1.7	0.97	0.98	0.053 (0.024-0.079)	0.044
Model 2c	9	87.8*	27	3.3	0.88	0.95	0.097 (0.075-0.120)	0.065

Notes: k=number of items; df=degrees of freedom; CFI=comparative fit index; GFI=goodness of fit index; RMSEA=root mean square error of approximation; SRMR=standardized root mean residual.
*p < 0.01.

3. RESULTS

4. DISCUSSION

The PHQ-9 has been widely used with various populations in Korea but not with early childhood education teachers. In addition, the PHQ-9’s underlying factor structure, as explained by previous research, was inconsistent. This study’s purposes were to evaluate the PHQ-9 Korean version’s factor structure and convergent validity among Korean early childhood education teachers. Using CFA to determine which model had the greatest empirical support, the study tested four models from the literature. Analytical results revealed that the two-factor model with three somatic items and six affective items, as identified in patients with spinal cord injury [18, 24], provided the best data fit. Although early childhood teachers might differ qualitatively from patients with spinal cord injuries, the PHQ-9’s finding of distinct subscales of depression in these two populations possibly resulted because somatic symptoms are considered their norm rather than an exception [34, 35]. In fact, the examination of somatic and affective scores showed that the current study’s participants scored a higher average on the somatic subscale.

Although the PHQ-9 was originally developed as a unidimensional structure [14], findings here suggest that the PHQ-9 should be used as a multidimensional depression instrument with early childhood teachers in Korea. Consistent with theory and prior research that has increasingly suggested depression as a multidimensional construct [36, 37], current findings confirm the PHQ-9’s multidimensionality.

As for psychometric properties, the PHQ-9’s Korean version exhibited adequate reliability. The internal consistency values of the scores on the two subscales and the total scores were adequate (α>0.70). In terms of convergent validity, the correlations of the scores on the two subscales and the total scores on the PHQ-9 and BDI-II were satisfactory overall and in line with other studies [38, 39]. This correlation was slightly higher than the Pearson’s correlation coefficient of 0.70 reported by Lim et al. [40] when they compared the same instruments in populations of general Korean adults. Hence, the PHQ-9 scores evidenced convergent validity by their degree of correlation with the measure of depression in the BDI-II. Specifically, the moderate correlation between the PHQ-9 and the BDI-II suggests that the PHQ-9’s constructs constitute a valid depression measure for this population. These findings are compatible with those of previous studies that also found a correlation between PHQ-9 scores and measures of depression. Similar to other reports, the current analyses showed that a two-factor model representing somatic and affective factors provided the best fit to the BDI-II data [19, 41, 42].

Findings should be interpreted in light of several limitations. First, the sample size was relatively small, and most of the participants were female teachers. The primary reason for this gender imbalance is the low number of men in the early childhood education workforce, as childcare has historically been viewed as women’s work. The widespread public belief that women are more nurturing and caring than men has served as a barrier discouraging men from considering a career in early childhood education [43]. Additionally, epidemiological studies have consistently reported that men and women experience depression in different ways due to such factors as biological (gender) differences, gender-based roles, and identity [44, 45]. Therefore, the models should be assessed by gender, as the structures of the PHQ-9 may differ between males and females. For example, one study reported significant inequalities between genders on the PHQ-9 in a sample of Norwegian adolescents [46]. Although women are considerably overrepresented in the teaching profession, especially in early childhood education settings, future evaluations of the PHQ-9 would benefit from larger samples with more male respondents. Next, early childhood teachers are at particularly high risk of poor mental health, and, indeed, study participants’ higher than average scores indicated high levels of depression. The PHQ-9’s structure might differ between samples from the general population and various occupational groups, so these results are not generalizable to the general population or to other professions. As mentioned earlier, teaching, in particular early childhood education, is considered a relatively stressful profession with high turnover rates; moreover, early childhood education teachers are a specific occupational group at high risk of mental health disorders. Future studies could compare the PHQ-9’s structure between nonclinical and clinical samples of early childhood teachers to provide a more concrete understanding of their depression symptomatology and better understanding of how the PHQ-9 can be applied within various populations.

Despite these limitations, current findings have implications for clinical practice. This brief and valid measure’s availability is critical for helping healthcare professionals identify early childhood teachers at high risk of depression. Also, important is that clinicians use screening tools acceptable and appropriate for the specific population. Clarification of this instrument’s proper use is a fundamental contribution to aiding prevention, early detection, and treatment of depression.

CONCLUSION

In conclusion, findings from this study highlight that the PHQ-9 Korean version is a robust measure of depression among early childhood education teachers. Previous studies have affirmed somatic and affective constructs, and no items have been problematic. Hence, the model with two specific factors, especially Krause et al. two-factor model provided the best fit to data, and convergent validity and internal consistency were satisfactory overall. The Korean version of the PHQ-9 can serve as a valid and reliable screening tool to detect depression in early childhood education teachers.

REFERENCES