Demographic characteristics
EPDS data of 1614 mothers with a mean age of 28.87 years (5.46) was included in the exploratory and confirmatory factor analyses. Complete data was not available for 86 mothers and thus, excluded from the study. A significant majority 1313 (81.4%) reported being in a non-consanguineous marriage and lived in a nuclear family 1320 (81.8%). Mean number of years of education received by mothers were reported to be 8.64 (3.83). Most of the mothers were housewives 1314 (81.4%), 22 (1.4%) were unqualified workers, 100 (6.2%) low to middle quality workers, 136 (8.54%) were qualified government workers and 42 (2.6%) were professional workers. Around half of the mothers delivered their current child with normal vaginal delivery (808, 50.1%) while rest (804, 49.8%) delivered through caesarean section.
Face and content validity
The participants generally reported good comprehensibility of the EPDS scale at the time of administration, pointing to a good face validity. Content validity however, was not assessed as it was done in a previous publication that details the forward and backward translation process and criterion validity of the questionnaire [4].
Descriptive statistics
Mean score on Edinburgh Postnatal Depression Scale (EDPS) was 6.64 (4.63). Visualization of histogram and normal Q-Q plot revealed some degree of non-normality where distribution of total scores on EPDS was mildly skewed (0.78) and non-kurtotic (0.42) (Fig. 1). Mean scores on individual items ranged from 0.08 for item 10 exhibiting fewer symptoms of suicidality to 1.39 for item 3 exhibiting self-blaming or guilt among mothers. Furthermore, symptoms of anxiety (Item 4) and panic (Item 5) were most reported by the mothers.
Overall, a total of 310 (19.2%) of the mothers screened positive for depressive symptoms. Symptoms of guilt were reported by 1246 (77.20%), anxiety 1120 (69.39%), panic 979 (60.66%), sadness 893 (55.34%), poor coping 743 (46.03%), lack of sleep 660 (40.89%), crying spells 650 (40.27%), anhedonia 240 (14.87%), decreased mood 230 (14.25%), and suicidal ideation 90 (5.58%). Floors and ceiling effects were not evident in total scores of EPDS scale with less 20% of the respondents scoring either the lowest or highest of the possible scores on EPDS. A total of 99 (6.1%) respondents reported the lowest score on EPDS while only 1 (0.1%) reported the highest scores on it. This indicates that psychometric testing using EPDS was fit to measure depressive symptoms and responsive to change without being impaired by floor and ceiling effects.
Reliability and convergent validity
Standardized Chronbach’s alpha for EPDS was 0.81with corrected item-total correlations ranging from 0.35 to 0.62. All the items had adequate item-total correlations, revealing no multicollinearity or singularity and were retained at this stage for exploratory factor analyses. Moreover, inter-item correlation matrix was run to ascertain convergent validity with all items exhibiting a correlation value of 0.2 with at least one other item. Moreover, other tests for reliability yielded adequate reliability of EPDS as assessed by McDonald’s Omega (0.81) and Mislevy & Bock (1990) reliability estimate of 0.83.
Factor Validity
Prior to running exploratory factor analyses, sampling adequacy was ascertained using the KMO statistics, yielding a good sampling adequacy (0.88), along with a significant Bartlett test of sphericity (χ2 = 3456.03, P < 0.001). Thereafter, observation of correlation matrix revealed that all EPDS items had yielded a correlation > 0.2, at least with one other item. Item 9 (crying spells) yielded highest correlation value of 0.54 with Item 8 (sadness). Thus, there were no issues of multicollinearity in the data. Sampling adequacy for each item was measured using KMO measure of sampling adequacy obtained in anti-image correlation matrix. It ranged from 0.863 (Item 1) to 0.915 (Item 7), therefore, yielding marvellous to meritorious KMO values for individual items. Therefore, all items were taken into exploratory factor analyses.
The criteria for determining the number of factors to retain was multifaceted and dependent on several factors including Eigen values > 1, Cattell’s Scree plot as well as more advanced methods such as parallel analysis, Hull’s method and MAP Velicer test. A total of 2 factors yielded an Eigen Value greater than 1.0 in present analysis. The first factor had an Eigen value of 3.68 explaining a variance of 36.77% while the second factor had an Eigen value of 1.10 leading to a cumulative 47.79% of variance explained by the two factors. However, Cattell’s Scree plot (Fig. 2) favoured a one-dimensional model, demonstrating a sharp drop in Eigen value, from first to second factor. This uni-dimensionality was further confirmed in more advanced statistical analyses such as Parallel analysis. Parallel Analysis was run based on minimum rank factor analysis with 500 replicates (Timmerman & Lorenzo-Seva, 2011). This simulation revealed that the mean of random percentage of variance (18.1%) explained by second factor was greater than the percentage of variance obtained through EFA (12.9%). These were further confirmed by Minimum Average Partial Velicer test as well as the Hull Method.
All the items revealed adequate communalities (> 0.20) except item 2 (enjoyment) and item 10 (self-harm). Their communalities were 0.16 and 0.19, however, these items were not dropped. All the items yielded moderate to strong factor loadings (Table 2). Minimum factor loading was for item 2 (0.40) and highest for item 8 (0.71).
Table 1
Internal consistency and item-total correlations for individual items on EPDS
Item | Mean | SD | Scale Mean if Item Deleted | Corrected Item-Total Correlation | Cronbach's Alpha if Item Deleted |
1. I have been able to laugh and see the funny side of things | 0.16 | 0.433 | 6.48 | 0.409 | 0.785 |
2. I have looked forward with enjoyment to things | 0.17 | 0.448 | 6.47 | 0.346 | 0.789 |
3.I have blamed myself unnecessarily when things went wrong | 1.39 | 0.954 | 5.25 | 0.455 | 0.779 |
4. I have been anxious or worried for no good reason | 1.16 | 0.934 | 5.49 | 0.545 | 0.765 |
5. I have felt scared or panicky for no very good reason | 1.02 | 0.980 | 5.63 | 0.483 | 0.775 |
6. Things have been getting on top of me | 0.83 | 1.003 | 5.82 | 0.507 | 0.772 |
7. I have been so unhappy that I have had difficulty sleeping | 0.62 | 0.857 | 6.02 | 0.474 | 0.775 |
8. I have felt sad or miserable | 0.71 | 0.802 | 5.93 | 0.619 | 0.756 |
9. I have been so unhappy that I have been crying | 0.50 | 0.707 | 6.15 | 0.578 | 0.763 |
10. The thought of harming myself has occurred to me | 0.08 | 0.339 | 6.57 | 0.369 | 0.790 |
Table 2
Factor loadings for individual items obtained with PFA and ML
Statements | PAF | ML | Communalities |
1. I have been able to laugh and see the funny side of things | 0.483 | 0.477 | 0.234 |
2. I have looked forward with enjoyment to things | 0.400 | 0.395 | 0.160 |
3.I have blamed myself unnecessarily when things went wrong | 0.493 | 0.493 | 0.243 |
4. I have been anxious or worried for no good reason | 0.592 | 0.591 | 0.350 |
5. I have felt scared or panicky for no very good reason | 0.512 | 0.506 | 0.262 |
6. Things have been getting on top of me | 0.567 | 0.562 | 0.322 |
7. I have been so unhappy that I have had difficulty sleeping | 0.535 | 0.536 | 0.286 |
8. I have felt sad or miserable | 0.714 | 0.721 | 0.510 |
9. I have been so unhappy that I have been crying | 0.674 | 0.681 | 0.454 |
10. The thought of harming myself has occurred to me | 0.434 | 0.435 | 0.188 |
Confirmatory Factor Analysis
Confirmatory Factor Analysis with the ML was run to confirm the goodness of fit for one-dimension structure of EPDS. It revealed that the one-dimension structure for EPDS yielded adequate values for all the indices representing the goodness of fit. It yielded a RMSEA value of 0.066 (< 0.08) which was not significantly greater than the cut-off value of 0.05. And according to Hair et al. (2010) and Hu & Bentler (1999), revealed a good fitness of the model. All goodness of fit indices > 0.90 including CFI (0.93), TLI (0.91), GFI (0.99), AGFI (0.98), and GFI without diagonal values (0.97).RMSR was 0.047 which was not significantly larger than the expected mean value of RMSR for an acceptable model, as obtained by the Kelley’s criterion (4/ √sample size).
Known group analysis with characteristics of mother
There was significant association of EPDS scores with improved housing index (r = 0.1, p < 0.05) and high income (r = 0.1, p < 0.05). There were no significant relationships between type of delivery (χ2 = 0.69, p > 0.05), mother’s education levels (P > 0.05) and age (P > 0.05).