The primary search yielded 151 potential studies. After screening the titles and abstracts, 34 studies were used for further assessment by reading the full-texts and extracted data. Among the 34 studies[13-18, 20, 25-51], a total of 21 studies were excluded[16, 31, 32, 34-51]: 11 were excluded for the objectives of the study were not about the association of abortion and suicide[31, 32, 40, 42-44, 46-48, 51]; 6 studies mentioned about the association of abortion with suicide risk, but no data could be extracted for data analysis[38, 41, 45, 49, 50]; 2 studies did not reported control groups and data could not be extracted[36, 37]; 1 study used the general population as the control group; 1 study did not report the suicide rate in the control group; 1 study was about the pregnancy outcome with suicide and cannot be used for data analysis in the current study; two studies were about abortion with risk of suicide in Finland[39, 52], the data may be duplicated in those two studies, thus we excluded the first study. Finally, a total of 13 studies were included for data analysis[13-15, 17, 18, 20, 25-30, 33]. The studies selection process is shown in Figure 1.
Study characteristics and risk of bias assessment
The characteristics of the included studies are shown in Table 1. The quality of the cross-sectional studies was evaluated by the AHRQ scale, and the results are shown in Table 2. The quality of the case-control and cohort studies were evaluated by the NOS, and the results are shown in Table 3.
A total of 4 studies reporting completed suicide as their outcome were included[13, 17, 28, 30]. The results of the meta-analysis showed that abortion might be associated with an increased risk of completed suicide(OR=3.16, 95CI 2.49 to 3.99, P<0.00001) (Figure 2).
A total of 4 studies reporting suicide behavior as their outcome were included[20, 26, 28, 33]. The results of the meta-analysis showed that abortion might be associated with an increased risk of suicide behavior (OR=1.92, 95CI 1.64 to 2.26, P<0.00001) (Figure 3).
A total of 7 studies reporting suicidal ideation as their outcome were included[14, 15, 18, 20, 25, 27, 29]. The results of meta-analyses showed that abortion was associated with an increased risk of suicide behavior (OR=1.52, 95CI 1.32 to 1.75, P<0.00001) (Figure 4).
Publication bias was assessed by using funnel plots. All funnel plots for the three outcomes were almost symmetrical, suggesting a low possibility of publication bias (Figure not shown).
For each outcome, the results are compared with the fixed-effect model and the random-effect model, and the consistency of the results can reflect the reliability of the combined results, indicating that the results of this study were reliable. In addition, the results were not obvious influenced when excluding each study, suggesting the stable of the results.