Table 1 presents descriptive statistics for the PHQ–4 scores in different gender groups. Skewness and kurtosis values ranged from -1.34 to .19, indicating the fact that the distribution of the PHQ–4 scores in these groups was normal. The reliability of the PHQ–4 was high (Cronbach's alpha ≥ .70) in all age groups among females and males (refer to Table 3). In the group of non-binary, only the depression subscale had low reliability (Cronbach's alpha = .34; refer to Table 1).
[Insert Table 1]
Factor structure and invariance measurement
The intended 2-factor model was an excellent fit (see Table 2). Factor loadings were high (anxiety subscale: item 1 = .732, item 2 = .817; depression subscale: item 3 = .739, item 4 = .920). The estimated covariance between the anxiety and the depression subscales was .870 (p < .001). The analyses showed that the 2-factor model was invariant regarding its configural, metric, and scalar invariance across different gender and age categories. In summary, the intended PHQ–4 factor structure and its invariance were supported empirically.
[Insert Table 2]
Age and gender differences in anxiety and depressive symptoms
Table 3 presents descriptive statistics for the PHQ–4 scores in different age and gender groups as well as the prevalence of positively screened participants in each of these groups. The Kruskal-Wallis H test showed the gender-differentiated anxiety (H(2) = 60.37, p < .001) and depression (H(2) = 9.79, p = .007) levels as well as the total PHQ–4 score (H(2) = 32.15, p < .001). Males had significantly lower anxiety scores, as well as the total ones, than females (anxiety: p < .001, total score: p < .001) and non-binary (anxiety: p = .002, total score: p = .004). Non-binary had significantly higher depression scores than males (p = .030), as well as total ones than females (p = .049).
Among females and males, different age groups differed in anxiety (females: (H(3) = 80.19, p < .001; males: H(3) = 17.22, p < .001), depression (females: H(3) = 82.91, p < .001; males: H(3) = 27.09, p < .001) and the total scores (females: H(3) = 95.04, p < .001; males: H(3) = 25.13, p < .001; refer to Table 3).
Females aged 18–29 had higher levels of anxiety, depressive and the total anxiety-depressive symptoms than females aged 30–44 (anxiety: p = .001, depression: p = .004, total score: p = .001), 45–59 (anxiety: p = .007, depression: p < .001, total score: p < .001) and females aged 60–78 (anxiety: p < .001, depression: p < .001, total score: p < .001). Females aged 60–78 had significantly lower anxiety scores and total ones than females aged 45–59 (anxiety: p = .001, total score: p = .008).
Males aged 60–76 had significantly lower anxiety and depressive symptoms than males aged 18–29 (p = .004 and p < .001, respectively) and 30–44 (all p < .001), and 45–59 (anxiety: p = .016, depression: p = .020), as well as lower levels of anxiety-depressive symptoms than males aged 18–29 (p < .001), 30–44 (p < .001) and 45–59 (p = .008; refer to Table 3).
[Insert Table 3]
Summarizing the results, females, non-binary and younger people in general experienced more symptoms of mental health conditions.
A series of one-way ANCOVAs was conducted to examine whether people in different education, marital status, residence, and main activity categories differ concerning the PHQ–4 results (age was used as a covariate for controlling its influence; see Table 4).
[Insert Table 4]
A series of one-way ANCOVAs showed that participants with lower educational levels and unemployed people scored higher on anxiety-depressive symptoms. As for marital status, being single was related to a significantly higher depression score. The place of residence did not alter the PHQ–4 scores. The detailed results are presented in Table 4.
Latent profile analysis for anxiety and depression symptoms
AIC and BIC indices decreased with adding a new class (Table 5). In general, in the profiles from 2 to 5, the entropy values were comparable in the samples of females and males with the highest value in the six-profile solution. However, the least numerous profile of the six-profile solution in the sample of males had less than 5% of respondents, which indicates the rejection of this solution. Thus, based on all the fit indices and theoretical and practical premises along with the meaningfulness of the extracted profiles, we identified four profile solutions in the samples of females and males as optimal and succinct.
[Insert Table 5]
The description of the four distinguished profiles in females and males is presented in Table 6. Figures 1 and 2 present the profiles graphically.
[Insert Table 6 and Figures 1 and 2]
The distinguished profiles in females and males are very similar according to their clinical meaningfulness and prevalence. We identified four common subpopulations among females and males with similarities in clinical meaningfulness. The first and the most numerous subpopulation is presented by Profile 3 in females and Profile 1 in males. It represents the subpopulation of Poles with low anxiety and depressive symptoms. The mean scores for anxiety and depression suggest negative screening results in both anxiety and depression. In our whole sample, about 37% of females and 39% of males had low levels of anxiety and depressive symptoms. The second subpopulation is presented by Profile 1 in females and Profile 4 in males. It represents a subpopulation of Poles with very high anxiety and very high depressive symptoms. The mean scores for anxiety and depression suggest positive screening results for both anxiety and depression. Thus, about 28% of females and 24% of males may suffer from anxiety and depressive disorders. The third subpopulation is presented by Profile 2 in females and Profile 3 in males. It represents a subpopulation of Poles with high anxiety symptoms and moderate depressive ones. The mean scores for anxiety and depression suggest positive screening results for anxiety and negative ones for depression. This subpopulation is made up of 16% of females and 23% of males. The fourth subpopulation is presented by Profile 4 in females and Profile 2 in males. It represents a subpopulation of Poles with moderate anxiety symptoms and high depressive ones. The mean scores of anxiety and depression in Profile 4 in females suggest positive screening results for both anxiety and depression. The mean scores for anxiety and depression in Profile 2 in males suggest the negative screening results for anxiety and positive ones for depression. This subpopulation is made up of 19% of females and 14% of males.
Summarizing the LPA results, four subpopulations are distinguished among females and males. There is (1) a non-anxious and non-depressed subpopulation, (2) a highly anxious and highly depressed subpopulation, (3) a highly anxious and moderately depressed subpopulation, and (4) a moderately anxious and highly depressed subpopulation.