Table 3.
GRADE assessment of evidence quality
| Quality assessment | Effect | Overall quality of evidence | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| No of studies | Study design | Risk of bias | Inconsistency | Indirectness | Imprecision | Publication bias | Other considerations | No of subjects | Relative (95% CI) | |
| Overall | ||||||||||
| 18 | observational studies | not serious | Serious a | not serious | not serious | detected | Very strong association b | 198,893 | OR 2.45 (1.33 4.52) | ⨁◯◯◯ VERY LOW |
| Major depression | ||||||||||
| 12 | observational studies | not serious | Serious a | not serious | not serious | detected | Very strong association b | 5336 | OR 2.92 (1.42 5.98) | ⨁◯◯◯ VERY LOW |
| Depression | ||||||||||
| 6 | observational studies | not serious | not serious | not serious | not serious | not detected | none | 193,557 | OR 1.41 (1.14 1.73) | ⨁⨁◯◯ LOW |
OR Odds ratio, CI Confidence interval
a The score was downgraded because substantial heterogeneity between studies was detected and could not be fully explained
b The score was upgraded because the magnitude of the effect was large (OR > 2 based on consistent evidence from at least two studies, with no plausible confounders)