Comparison 3. Analgesic plus caffeine versus analgesic alone by dose of caffeine.

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Primary outcome	16		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only
1.1 Caffeine < 70 mg	5	596	Risk Ratio (M‐H, Fixed, 95% CI)	1.14 [0.97, 1.34]
1.2 Caffeine 70 mg to 150 mg	14	2983	Risk Ratio (M‐H, Fixed, 95% CI)	1.21 [1.12, 1.32]
1.3 Caffeine > 150 mg	6	745	Risk Ratio (M‐H, Fixed, 95% CI)	1.21 [1.07, 1.35]