Summary of findings for the main comparison. SSRIs for premenstrual syndrome: all symptoms (end scores).

SSRIs compared to placebo ‐ all symptoms (end scores) for premenstrual syndrome
Patient or population: women with premenstrual syndrome Settings: community or outpatient Intervention: SSRIs Comparison: placebo ‐ all symptoms (end scores)
Outcomes	Illustrative comparative risks* (95% CI)	No of Participants (studies)	Quality of the evidence (GRADE)	Comments
Moderate dose SSRI versus placebo Luteal or continuous administration	The mean score for all symptoms in the intervention groups was 0.67 standard deviations lower (0.46 to 0.84 lower)	1276 (9 studies)	⊕⊕⊝⊝ low1,2	SMD ‐0.65 (95% CI ‐0.42 to ‐0.84) Symptoms were significantly less severe in the SSRI group. The size of the effect was moderate.
Moderate dose SSRI versus placebo Luteal administration	The mean score for all symptoms in the intervention groups was 0.51 standard deviations lower (0.71 to 0.31 lower)	457 (4 studies)	⊕⊕⊕⊝ moderate2	SMD 0.51 (95% CI ‐0.71 to ‐0.31) Symptoms were significantly less severe in the SSRI group. The size of the effect was moderate.
Moderate dose SSRI versus placebo Continuous administration	The mean score for all symptoms in the intervention groups was 0.72 standard deviations lower (0.97 to 0.47 lower)	843 (7 studies)	⊕⊕⊝⊝ low1,2	SMD ‐0.72 (95% CI ‐0.97 to ‐0.47) Symptoms were significantly less severe in the SSRI group. The size of the effect was moderate.
*The basis for the assumed risk is the median control group risk across studies. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; SMD standardised mean difference
GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate.

¹ Only 4/9 studies overall (2/4 of luteal and 3/7 of continuous administration) described adequate methods of randomisation and allocation concealment; 8/9 studies were at uncertain or high risk of attrition bias.
 ² Substantial overall heterogeneity (I squared= 58%), attributable to heterogeneity in continuous administration group (I squared=68%), which included two studies with larger intervention effects. No obvious explanation (though studies used wide variety of assessment tools).