Study characteristics
Study characteristics and the prevalence of depression in each study are presented in Table 1. All 26 included studies reported a point prevalence of depression, whereas two studies reported the lifetime prevalence of depression in addition to the point prevalence. The sample size in individual studies ranged from 92 to 18182 (median = 816). Regarding age groups, five studies reported findings from adult populations, four studies among older persons, and six studies among young persons. Eleven studies reported findings from maternal (i.e., antenatal and postnatal) populations. The percentage of females in individual studies (excluding maternal populations) ranged from 44.6–75.6%. Out of the 26 included studies, 24 used a validated self-report tool, and three studies used a diagnostic interview to detect depression[11, 22, 23]. Among the screening instruments, the most frequently used ones were Edinburgh Postnatal Depression Scale (EPDS) (10 studies), Geriatric Depression Scale (GDS-15) (4 studies), Center for Epidemiological Studies-Depression Scale (CES-D) (3 studies),Depression Anxiety and Stress Scale(DASS-21) (3 studies), and Patient Health Questionnaire (PHQ-9) (2 studies); Hopkins Symptoms Checklist (HSCL) and Hospital Anxiety and Depression Scale (HADS) were used in one study each. The three studies which used diagnostic interviews utilised the Composite International Diagnostic Interview (CIDI) and Structured Clinical Interview for DSM Disorders(SCID).
Risk of bias in studies
All the 26 studies were adjudged to have a low risk of bias according to the risk of bias tool developed by Hoy et al. The risk of bias assessments are presented in Table 2.
Table 2
Study
|
Score
|
Level of risk
|
Young persons
|
Amarasuriya, Jorm and Reavley (2015)
|
2
|
Low risk
|
Gamage et al. (2021)
|
2
|
Low risk
|
Kodagoda and Meegoda (2020)
|
2
|
Low risk
|
Perera et al. (2006)
|
3
|
Low risk
|
Rodrigo et al. (2010)
|
1
|
Low risk
|
Rathnayake and Ekanayaka (2016)
|
3
|
Low risk
|
Adults
|
Ball et al. (2010)
|
1
|
Low risk
|
Ferdinando et al. (2020)
|
2
|
Low risk
|
Institute for Research and Development in Health and Social Care (2007)
|
2
|
Low risk
|
Jayasuriya et al. (2016)
|
0
|
Low risk
|
Rodrigo, Kuruppuarachchi and Pathmeshwaran (2015)
|
3
|
Low risk
|
Older persons
|
|
|
Khaltar et al. (2017)
|
3
|
Low risk
|
Malhotra,Chan and Ostbye (2010)
|
0
|
Low risk
|
Rajapakshe,Sivayogan and Kulatunga (2019)
|
1
|
Low risk
|
Senadheera et al. (2017)
|
3
|
Low risk
|
Maternal population
|
Agampodi et al. (2011)
|
2
|
Low risk
|
Agampodi and Agampodi (2013)
|
1
|
Low risk
|
Arachchi et al. (2019)
|
3
|
Low risk
|
Fan et al. (2020)
|
3
|
Low risk
|
Herath, Sivayogan and Balasuriya (2016)
|
1
|
Low risk
|
Herath,Balasuriya and Sivayogan (2017)
|
3
|
Low risk
|
Jayakody (2015)
|
2
|
Low risk
|
Jayasinha and Perera (2019)
|
2
|
Low risk
|
Palfreyman (2021)
|
1
|
Low risk
|
Patabendige et al. (2020)
|
3
|
Low risk
|
Wijesooriya (2015)
|
2
|
Low risk
|
Prevalence of depression
The point prevalence of depression in individual studies ranged from1.6–61%. The total number of participants in the 26 studies was 49217, and the number of cases of depression was 8759. When pooled using a random-effects model, the aggregate point prevalence of depression was 20.3% [14.76–27.23%]. A high degree of heterogeneity was present among the studies (I2 = 99.2% [95% CI: 99.1%; 99.3%]; tau2 = 0.9894; Q = 3220.4, p < 0.001). The forest plot with studies grouped according to subpopulations is shown in Fig. 2.The pooled lifetime prevalence of depression based on two studies[11, 23]was 6.76% (95% CI: 6.19–7.38%).
Subgroup and sensitivity analysis
The pooled point prevalence rates of depression were calculated separately for the four subpopulations (Fig. 2): adults (8.66% [3.9–18%], k = 5, n = 32121, I2 = 99.7%, Q = 1248), young persons (40.88% [95% CI: 24.77–59.21%, k = 6, N = 6614, I2 = 99.6%, Q = 1279), older persons (18.44% [10.75–29.8%], k = 4, N = 3323, I2 = 97.7%, Q = 129.8), and maternal populations (19.66% [95% CI: 14.87–25.53%], k = 11, N = 4321,, I2 = 96.3%, Q = 268). These subgroup differences were statistically significant (Q = 12.46, p = 0.006).
A subgroup analysis was conducted to compare the prevalence rates in studies that used self-report instruments versus diagnostic interviews. The pooled prevalence of depression in self-report-based studies and interview-based studies were 22.75% (95% CI: 17.32–29.27%, I2 = 99.1%, Q = 2428) and 4.31%(95% CI: 1.06–15.910-28%], I2 = 99.5%, Q = 201), respectively. This difference was statistically significant (Q = 6.23, p = 0.0126).
In a sensitivity analysis where the maternal populations were excluded, the pooled prevalence remained largely unchanged (20.85%; 95% CI: 12.44–32.8%)
Moderator analysis
A moderator analysis was conducted to assess whether the percentage of females in the sample and the year of publication moderated the prevalence estimates and heterogeneity. Neither the female percentage (regression coefficient = -0.0013, p = 0.364) nor the publication year (regression coefficient = -0.0002, p = 0.981) significantly moderated the studies’ effect sizes. The heterogeneity accounted for by these two moderator variables (R2) was close to zero.
Publication bias
The distribution of studies in the funnel plot was asymmetrical (Fig. 3), indicating substantial publication bias. Egger’s test statistically affirmed significant asymmetry of the funnel plot (t = 4.06, p = 0.0004, intercept = 0.0315 [SE = 0.0206]).
Associated factors
Associated factors were categorised into individual attributes and behaviours, social and economic circumstances, and broader environmental factors. The life course approach used in the original WHO discussion paper was followed according to the subgroups[21].
Young persons
Most studies showed no association between gender and depression among young persons[24–27]. Being older was associated with depression among university students [25, 28]. Students in senior grades in schools and senior batches in universities were more likely to show depressive symptoms [25, 26, 28, 29]. Tobacco use among male school students, alcohol use among both male and female students, and low physical activity among female students were significantly associated with depression [24]. Stress and anxiety were common associations with depression among university students [27, 28].
Concerning the immediate socio-economic circumstances,Amarasuriya et al. [25]reported that exposure to physical threats, family deaths, romantic break-ups, a problem with a close associate, educational difficulties, unemployment and domestic violence were significantly associated with depression among university students. Harassment by peers was an associated factor only among male students. The likelihood of depression was positively correlated with the frequency of exposure to threatening life events among these students[25].
Adult
Female gender and older age were identified as individual attributes that showed associations with depression in adults [11, 23, 30]. Ball et al. [11] studied the genetic and environmental contributions to depression as part of the CoTASS study and reported a higher genetic contribution in females (61%) than males (4%).Ethnicity showed mixed results, with one study showing increased odds among the Sinhalese majority[11], whereas another study reported belonging to an ethnic minority to be associated with depression[30].
Being widowed, separated or divorced increased the odds of having depression [11]. Abuse by the partner and lack of perceived social support were also associated with depression [23, 30]. Lower educational status was another factor associated with adult depression[23, 30].Self-rated financial difficulty and indebtedness were associated with depression [11, 23]. Ferdinando et al. [23]identified unemployment to be significantly associated with depression. However, according to Ball et al.[11], underemployment was significantly associated with depression only among males with lower living standards. In contrast, being employed was an associated factor for depression among females with lower living standards[11].
According to Ball et al.[11], the urban environment was associated with depression in men but not in women; they further reported that lower standards of living, including poor-quality structural material, poor-quality water and toilets, were associated with depression among males. In many studies, food insecurity was associated with adult depression[11, 23, 30]. At more structural levels, living in zones of civil conflicts and poor access to health care were associated with depression [30].
Older persons
Association between gender and depression among older persons was inconsistent. Three studies showed no significant relationship[31–33], whereas Rajapakshe et al. [34]found female gender as the strongest associated factor by multivariable analyses. Another study showed more complex gender-ethnicity interactions with depression where only males in the ethnic minorities had increased odds of depression compared to males in the majority [32]. With regard to age, the ‘young old’ and ‘middle old’ categories were seen to have more odds of depression compared to the ‘oldest old’ categories [32, 34]. However, this association with age lost its significance when adjusted for the health status of the participants [32]. Chronic diseases were frequently associated with depression among older persons[31, 32, 34]. However, when adjusted for independent activities of daily living, this association was not significant[32]. Smoking and alcohol use were also associated with geriatric depression [34].
Low-income status and lack of social support were frequently associated with depression among older persons[31, 32, 34]. Being unmarried, widowed, separated, or divorced and experiencing abuse increased the odds of depression among older persons [34]. Post-primary education protected older persons against depression [32].
Maternal population
The association of depression with maternal age and parity was inconclusive. Arachchi et al., Agampodi et al., and Palfreyman [35–37]detected no significant association between maternal age and parity. However, in other studies, advanced maternal age, primiparity and multiparity over three pregnancies were associated with depression [38–40]. Association with ethnicity was not significant [36, 37]. Association with maternal diseases and pregnancy complications gave varied results [39–41]. Mothers’ previous history of suicidal ideation was frequently associated with depression [35–37].
The husband’s lack of support and exposure to intimate partner violence were frequently associated with maternal depression [37, 41, 42]. Jayasinha and Perera[41] identified a weak negative correlation between marital satisfaction and depression among antenatal mothers. Both low and high-income statuses were associated with maternal depression[40, 41, 43]. Studies failed to detect any association of depression with employment and education level of mothers[36, 40, 41]. Palfreyman [37] and Fan et al.[39] reported that having an employed spouse protected mothers against depression.