Table 5.

Effect estimates, event rates, and NNHs of meta-analyses examining medical cannabinoids versus placebo for adverse events

TYPE OF ADVERSE EVENTSTUDYNO. OF RCTS (NO. OF PARTICIPANTS)RELATIVE EFFECT ESTIMATE (95% CI), HETEROGENEITYRE-ANALYSIS EFFECT ESTIMATE (95% CI), HETEROGENEITYCANNABINOID EVENT RATEPLACEBO EVENT RATENNH
OverallLobos Urbina and Peña Duran, 201617NROR = 3.03 (2.42 to 3.80), I2 = 44%NA92%78%8
Meza et al, 2017294 (1025)RR = 1.18 (1.10 to 1.27), I2 = NRNANRNRNA
Wade et al, 2010283 (666)NRRR = 1.42 (1.27 to 1.59),* NA79%56%5
Wang et al, 20083023 (2068)Rate ratio of 1.86 (1.57 to 2.21), I2 = 87%NA10.4 per patient-year6.9 per patient-yearNA
Whiting et al, 2015229 (3714)OR = 3.03 (2.42 to 3.80), I2 = 31%RR = 1.30 (1.21 to 1.39), I2 = 53%81%62%6
SeriousMücke et al, 2016196 (1031)RR = 1.15 (0.88 to 1.49), I2 = NRNA26%17%NS
Petzke et al, 20161611 (1568)RD = 1% (−1% to 3%), I2 = NRNA6.3%17%NS
Wang et al, 20083023 (2068)Rate ratio 1.04 (0.78 to 1.39), I2 = NRNA0.37 per patient-year0.25 per patient-yearNA
Whiting et al, 2015234 (3248)OR = 1.41 (1.04 to 1.92), I2 = 0%NANRNRNA
WithdrawalSmith et al, 2015252 (276)RR = 6.85 (1.96 to 23.99), I2 = 0%NA14%1%8
Tramèr et al, 20012719 (1111)RelR = 4.67 (3.07 to 7.09), I2 = NRNA11%2%11
Mücke et al, 2016196 (1031)RR = 1.20 (0.85 to 1.71), I2 = NRNA15%11%NS
Petzke et al, 20161611 (1574)RD = 0.04 (0.01 to 0.07), I2 = 22%RR = 2.03 (1.43 to 2.88), I2 = 0%11%5%19
Iskedjian et al, 2007187 (508 observations)NANA4.3%3.6%NA
Koppel et al, 20143124 (2737)NRNA7%2%22
Wade et al, 2010283 (666)NRRR = 3.04 (1.59 to 5.81),* NA11%4%14
Whiting et al, 2015223 (2755)OR = 2.94 (2.18 to 3.96), I2 = 2%NANRNRNA
SedationSmith et al, 2015252 (139)RR = 4.47 (0.35 to 57.81), I2 = 72%NA59%25%NS
Tramèr et al, 20012715 (1373)RelR = 1.66 (1.46 to 1.89), I2 = NRNA50%30%5
Whiting et al, 2015226 (3168)OR = 2.83 (2.05 to 3.91) I2 = 27%NANRNRNA
“Feeling high”Smith et al, 2015253 (137)RR = 31.10 (6.37 to 151.85), I2 = 0%NA70%0%2
Tramèr et al, 2001278 (1032)RelR = 10.6 (6.86 to 16.5), I2 = NRNA35%3%4
DysphoriaSmith et al, 2015252 (96)RR = 9.00 (0.50 to 160.59), I2 = NANA8%0%NS
Tramèr et al, 20012710 (690)RelR = 8.06 (3.38 to −19.2), I2 = NRNA13%0.3%8
Martin-Sanchez et al, 2009144 (343)OR = 2.56 (0.66 to 9.92), I2 = 0%RR = 2.85 (0.74 to 10.93), I2 = 0%4%1%NS
EuphoriaMartin-Sanchez et al, 2009144 (202)OR = 4.11 (1.33 to 12.72), I2 = 0%RR = 3.67 (1.02 to 13.13), I2 = 0%15%2%9
Whiting et al, 2015227 (2420)OR = 4.08 (2.18 to 7.64), I2 = 49%NANRNRNA
Blurred vision or visual hallucinationTramèr et al, 20012710 (859)RelR = 6.10 (2.41 to 15.4), I2 = NRNA6%0%17
Martin-Sanchez et al, 2009145 (296)OR = 8.34 (4.63 to 15.03), I2 = 0%RR = 4.93 (2.54 to 9.58), I2 = 0%44%8%3
Whiting et al, 2015210 (898)OR = 2.19 (1.02 to 4.68), I2 = 0%NANRNRNA
TinnitusMartin-Sanchez et al, 2009142 (152)OR = 2.18 (0.93 to 5.11), I2 = 0%RR = 2.11 (0.69 to 6.41), I2 = 0%16%7%NS
Disorientation or confusionMartin-Sanchez et al, 2009145 (508)OR = 3.24 (1.51 to 6.97), I2 = 0%RR = 2.85 (1.25 to 6.47), I2 = 0%9%2%15
Whiting et al, 2015212 (1736)OR = 5.41 (2.61 to 11.19), I2 = 0%NANRNRNA
Dissociation or acute psychosisTramèr et al, 2001276 (571)RelR = 8.58 (6.38 to 11.5), I2 = NRNA5%0%20
Martin-Sanchez et al, 2009144 (277)OR = 3.18 (0.89 to 11.33), I2 = 0%RR = 3.96 (0.90 to 17.40), I2 = 0%5%0%NS (20)†
Whiting et al, 201522 (37)OR = 1.09 (0.07 to 16.35), I2 = 25%NANRNRNA
Speech disordersMartin-Sanchez et al, 2009143 (200)OR = 4.13 (2.08 to 8.20), I2 = 0%RR = 2.91 (1.28 to 6.64), I2 = 0%32%7%5
Ataxia or muscle twitchingMartin-Sanchez et al, 2009146 (540)OR = 3.84 (2.49 to 5.92), I2 = 39%RR = 2.43 (1.61 to 3.67), I2 = 0%30%11%6
Whiting et al, 201526 (920)OR = 2.62 (1.12 to 6.13), I2 = 0%NANRNRNA
NumbnessMartin-Sanchez et al, 2009144 (226)OR = 3.98 (1.87 to 8.49), I2 = NRRR = 3.47 (1.34 to 9.00), I2 = 0%21%4%6
Impaired memoryMartin-Sanchez et al, 2009142 (227)OR = 3.45 (1.19 to 9.98), I2 = NRRR = 3.41 (0.95 to 12.27), I2 = 0%11%2%NS (12)†
Disturbance in attention or disconnected thoughtsMartin-Sanchez et al, 2009145 (381)OR = 5.12 (2.34 to 11.21), I2 = NRRR = 4.29 (1.75 to 10.53), I2 = 0%17%2%7
DizzinessMücke et al, 2016194 (823)RD = 3% (−2% to 8%), I2 = NRNA14%11%NS
Wade et al, 2010283 (666)NRRR = 2.87 (2.02 to 4.08),* NA32%11%5
Whiting et al, 2015241 (4243)OR = 5.09 (4.10 to 6.32), I2 = 18%NANRNRNA
NauseaWhiting et al, 2015230 (3579)OR = 2.08 (1.63 to 2.65), I2 = 0%NANRNRNA
DiarrheaWhiting et al, 2015217 (2077)OR = 1.65 (1.04 to 2.62), I2 = 15%NANRNRNA
FatigueWhiting et al, 2015220 (2171)OR = 2.00 (1.54 to 2.62), I2 = 0%NANRNRNA
Central nervous systemPetzke et al, 2016169 (1304)RD = 36% (14% to 59%), I2 = NRNA60%27%4
PsychiatricMücke et al, 2016195 (763)RD = 1% (−2% to 4%), I2 = NRNA4%3%NS
Petzke et al, 2016169 (1304)RD = 11% (6% to 16%), I2 = NRNA17%5%9
Wade et al, 2010283 (666)NRRR = 3.29 (1.98 to 5.48),* NA19%6%8
Dry mouthWhiting et al, 2015236 (4181)OR = 3.50 (2.58 to 4.75), I2 = 28%NANRNRNA
DepressionWhiting et al, 2015215 (2353)OR = 1.32 (0.87 to 2.01), I2 = 0%NANRNRNA
AnxietyWhiting et al, 2015212 (1242)OR = 1.98 (0.73 to 5.35), I2 = 54%NANRNRNA
VomitingWhiting et al, 2015217 (2191)OR = 1.67 (1.13 to 2.47), I2 = 0%NANRNRNA
Asthenia or weaknessWhiting et al, 2015215 (1717)OR = 2.03 (1.35 to 3.06), I2 = 0%NANRNRNA
DyspneaWhiting et al, 201524 (375)OR = 0.83 (0.26 to 2.63), I2 = 0%NANRNRNA
HypotensionTramèr et al, 20012713 (982)RelR = 2.23 (1.75 to 2.83), I2 = NRNA25%11%8

  • NA—not applicable, NNH—number needed to harm, NR—not reported, NS—not significant, OR—odds ratio, RCT—randomized controlled trial, RD—risk difference, RelR—relative risk, RR—risk ratio, RCT—randomized controlled trial.

  • ↵* Preplanned pooling of 3 studies. Combined data available, so RR was calculated without formal meta-analysis.

  • ↵† Confidence intervals suggest that benefit is likely, so estimated NNH provided.