The risk of suicidal ideation among current smokers versus nonsmokers is shown in Fig 2. According to this forest plot, there was a significant association between cigarette smoking and suicidal ideation. Current smoking was reliably associated with suicidal ideation. The overall estimate of OR was 2.05 (95% CI: 1.53, 2.58) based on cohort studies and 1.98 (95% CI: 1.72, 2.23) based on case-control/cross-sectional studies. The between-study heterogeneity was high for both groups of studies (P<0.001, I2 = 80.8% and I2 = 81.5%, respectively).
