The subgroup analyses are shown in appendix 4 for the primary outcomes of depression and suicidal ideation. Subgroup tests showed no evidence of a variation in the side effects of depression and suicidal ideation by age group (P=0.391 and P=0.933, respectively, for interaction), percentage of men in the study (P=0.418 and P=0.925), percentage of white people in the study (P=0.685 and P=0.254), presence or absence of psychiatric illness (P=0.126 and P=0.304), smoking status (P=0.906 for depression but not calculated for suicidal ideation as there were no reports of suicidal ideation in studies that included non-smokers), and whether the trial was industry sponsored or not (P=0.386 and P=0.380). The effect estimates (odds ratio) for the trials in which all participants had psychiatric illnesses compared with those where none of the participants had psychiatric illness were 1.49 (95% confidence interval 0.84 to 2.65) versus 0.91 (0.69 to 1.21) for depression and 0.79 (0.32 to 1.93) versus 0.34 (0.09 to 1.29) for suicidal ideation.
