Table 2.

Effect estimates, event rates, and NNTs for meta-analyses examining medical cannabinoids versus placebo for pain

SYSTEMATIC REVIEWTYPE OF PAINOUTCOMENO. OF RCTS (NO. OF PARTICIPANTS)AUTHORS’ META-ANALYSIS RESULT (95% CI), HETEROGENEITYMETA-ANALYSIS RE-ANALYZED (95%CI), HETEROGENEITYCANNABINOID EVENT RATECONTROL EVENT RATENNT
Whiting et al, 20152Chronic≥ 30% reduction in pain8 (1370)OR = 1.41 (0.99 to 2.00), I2 = 48%RR = 1.23 (0.98 to 1.56), I2 = 51%37%31%NS (approximately 19)*
Pain score on NRS from 0–106 (948)WMD = 0.46 (0.11 to 0.80), I2 = 59%NANANANA
Score on pain inventory from 0–103 (613)WMD = 0.17 (−0.16 to 0.50), I2 = 0%NANANANA
Score on neuropathic pain scale from 0–1005 (764)WMD = 3.89 (0.47 to 7.32), I2 = 41%NANANANA
Martin-Sanchez et al, 200914ChronicPain7 (278)SMD = 0.61 (0.37 to 0.84), I2 = 0%NANANANA
Andreae et al, 201515Neuropathic≥ 30% reduction in pain5 (405)OR = 3.22 (1.59 to 7.22), I2 = NRRR = 1.62 (1.24 to 2.12), I2 = 2%47%29%6
Petzke et al, 201616Neuropathic≥ 30% reduction in pain9 (1346)RD = 0.10 (0.03 to 0.19), I2 = 38%RR = 1.34 (1.04 to 1.74), I2 = 52%38%30%14
≥ 50% reduction in pain6 (737)RD = 0.05 (0.0 to 0.11), I2 = 44%RR = 1.48 (0.77 to 2.84), I2 = 44%19%16%NS
Average pain intensity13 (1575)SMD = 0.1 (0 to 0.2), I2 = 0%NANANANA
Lobos Urbina and Peña Duran, 201617Cancer≥ 30% reduction in pain2 (290)RR = 1.35 (0.63 to 2.09), I2 = NRNANRNRNA
Iskedjian et al, 200718MSChange in pain on VAS from 0–107 (298)0.8 more pain reduction (P = .03), I2 = 0NA6.2 baseline, improved 1.66.4 baseline, improved 0.8NA
Mücke et al, 201619Palliative≥ 30% reduction in pain2 (537)RD = 0.07 (−0.01 to 0.16), I2 = 0%RR = 1.34 (0.96 to 1.86), I2=0%30%23%NS
All studiesChronic≥ 30% reduction in pain15 (1985)NARR = 1.37 (1.14 to 1.64), I2 = 43%39%30%11
  • MS—multiple sclerosis, NA—not applicable, NNT—number needed to treat, NR—not reported, NRS—numeric rating scale, NS—not significant, OR—odds ratio, RCT—randomized controlled trial, RD—risk difference, RR—risk ratio, SMD—standardized mean difference, VAS—visual analogue scale, WMD—weighted mean difference.

  • * Confidence intervals suggest that benefit is likely, so estimated NNT provided.

  • Included only inhaled medical marijuana RCTs.