| Author/country | Intervention | Participant selection | No. of participants | Participant characteristics | Reported outcomes | Quality* |
|---|---|---|---|---|---|---|
| Cone et al.,22 2015, United States | Intervention: nonsmokers were exposed to marijuana smoke from participants smoking marijuana in controlled environment laboratory over 3 sessions; potency and ventilation of environment were changed between each session Multiple trials: 1) 5.3% THC in unventilated environment, 2) 11.3% THC in unventilated environment, 3) 11.3% THC in ventilated environment | Participant selection: recruited through newspaper advertisements, flyers posted on university campus and around community, and word of mouth Inclusion criteria for smokers: self-reported use of cannabis at least 2 times per week during previous 90 d, negative results of testing for other illicit substances Inclusion criteria for nonsmokers: healthy participants who self-reported lifetime cannabis use but had not used cannabis or any other illicit drug in previous 6 mo | 6 smokers | NR | THC level in oral fluid and whole blood, self-report of drug effects (Drug Effects Questionnaire visual analogue scale) | 22 |
| 6 nonsmokers | NR | |||||
| Cone et al.,23 2015, United States | Intervention: nonsmokers were exposed to marijuana smoke from participants smoking marijuana in controlled environment laboratory over 3 sessions; potency and ventilation of environment were changed between each session Multiple trials: 1) 5.3% THC in unventilated environment, 2) 11.3% THC in unventilated environment, 3) 11.3% THC in ventilated environment | Participant selection: recruited through newspaper advertisements, flyers posted on university campus and around community, and word of mouth Inclusion criteria for smokers: self-reported use of cannabis at least 2 times per week during previous 90 d, negative results of testing for other illicit substances Inclusion criteria for nonsmokers: healthy participants who self-reported lifetime cannabis use but had not used cannabis or any other illicit drug in previous 6 mo | 8 smokers | 3 women, 5 men, average age 29 (SD 6) yr, average BMI 25.6 | Total cannabis use (weight), THC level in urine | 22 |
| 18 nonsmokers | 9 women, 9 men, average age 28 (SD 7) yr, average BMI 24.7 | |||||
| Cone et al.,19 1987, United States | Intervention: nonsmokers were exposed to marijuana cigarette smoke (2.8% THC) under double-blind conditions Multiple trials: 3 trials, 1 with 4 cigarettes and 2 with 16 cigarettes | Participant selection: NR Inclusion criteria for nonsmokers: healthy, drug-free men with history of marijuana use who had 14 consecutive d of cannabinoid-free urine tests; 2 cannabis-naive men (members of research team) | 7 nonsmokers | All men, average age 36 yr, average weight 74.7 kg | Room air THC concentrations, THC level in urine | 20 |
| Cone et al.,25 1986, United States | Intervention: nonsmokers were exposed to marijuana cigarette smoke (2.8% THC) under double-blind conditions Multiple trials: 3 trials, 1 with 4 cigarettes and 2 with 16 cigarettes | Participant selection: NR Inclusion criteria for nonsmokers: healthy, drug-free men with history of marijuana use who had 14 consecutive d of cannabinoid-free urine tests; 2 cannabis-naive men | 7 nonsmokers | All men, average age 36 yr, average weight 74.7 kg | THC level in urine (EMIT 20 ng/mL and 100 ng/mL) and whole blood, heart rate, blood pressure, subscales of Addiction Research Center Inventory (single-dose questionnaire, visual analogue scale) | 22 |
| Cone et al.,26 1986, United States | Intervention: nonsmokers were exposed to marijuana cigarette smoke (2.8% THC) under double-blind conditions Multiple trials: 3 trials, 1 with 4 cigarettes and 2 with 16 cigarettes | Participant selection: NR Inclusion criteria for nonsmokers: healthy, drug-free men with history of marijuana use who had 14 consecutive d of cannabinoid-free urine tests; 2 cannabis-naive men | 7 nonsmokers | All men, average age 36 yr, average weight 74.7 kg | THC level in urine (EMIT 20 ng/mL and 100 ng/mL) and whole blood, subscales of Addiction Research Center Inventory (single-dose questionnaire, visual analogue scale, circular lights task, digit-symbol substitution task) | 19 |
| Herrmann et al.,24 2015, United States | Intervention: nonsmokers were exposed to marijuana smoke from participants smoking marijuana in controlled environment laboratory over 3 sessions; unlimited marijuana was provided to smokers Multiple trials: 1) 11.3% THC in unventilated environment, 2) 11.3% THC in ventilated environment (11 air exchanges per hour) | Participant selection: recruited from Baltimore through media advertising and word of mouth Inclusion criteria for smokers: age 18-45 yr, used cannabis at least 2 times per week during previous 90 d, urine sample positive for THC and negative for other drugs, negative breath alcohol reading at screening and on day of session, BMI 19-34, not pregnant or nursing Inclusion criteria for nonsmokers: age 18-45 yr, cannabis use at least once but not during previous 6 mo, urine sample negative for all drugs, negative breath alcohol reading at screening and on day of session, BMI 19-34, not pregnant or nursing | 7 smokers | 4 men, 3 women, average age 29.4 (SD 5.8) yr, average BMI 25.6 | Total weight of cannabis smoked, THC level in blood and urine, heart rate, blood pressure, subscales of Drug Effects Questionnaire (divided attention task, digit-symbol substitution task, paced auditory serial addition task) | 22 |
| 12 nonsmokers | 3 men, 3 women, average age 28.7 yr, average BMI 25.3 | |||||
| Law et al.,27 1984, United Kingdom | Intervention: nonsmokers were exposed to marijuana smoke (9.8% THC) in a small, unventilated room Multiple trials: No Timeline of exposure: after smokers had consumed their cannabis cigarette (which took 10-34 min), nonsmoking participants remained in room for 3 h | Participant selection: NR Inclusion criteria for smokers: NR Inclusion criteria for nonsmokers: NR | 6 smokers | NR | Environmental exposure (gas chromatography), THC level in urine and whole blood (radioimmunoassay) | 13 |
| 4 nonsmokers | NR | |||||
| Moore et al.,28 2011, United States | Intervention: passive 3-h exposure to marijuana in Dutch "coffee shop" Multiple trials: 2 trials in 2 different coffee shops, with varying numbers of active smokers (varying THC percentage) | Participant selection: volunteers; selection strategy NR Inclusion criteria for smokers: any active smoker in coffee shop during exposure timeline Inclusion criteria for nonsmokers: healthy participants who did not smoke marijuana | 16 smokers in trial 1, 6 smokers in trial 2 | NR | Air cannabinoid content (Quantisal collection device), THC level in oral fluid (Quantisal collection device) | 19 |
| 10 nonsmokers | 5 men, average age 22.8 yr, average weight 84 kg, average height 1.9 m, average BMI 233; 5 women, average age 23.8 yr, average weight 62.4 kg, average height 1.71 m, average BMI 21.2 | |||||
| Mørland et al.,33 1985, Norway | Intervention: participants were exposed to marijuana and hashish smoke in small, unventilated car Multiple trials: 1) hashish (1.5% THC), 2) marijuana (1.5% THC) | Participant selection: volunteers; selection strategy NR Inclusion criteria for smokers: NR Inclusion criteria for nonsmokers: healthy cannabis-naive participants | 5 smokers | NR | Blood cannabinoid levels (radioimmunoassay), THC level in urine (EMIT) | 16 |
| 10 nonsmokers | 7 men, 3 women "of normal weight in relation to their height, age, and sex" | |||||
| Mulé et al.,29 1988, United States | Intervention: in first part of experiment, smokers were asked to smoke cannabis as they usually did and were observed; in second part, nonsmokers were exposed to smoke of 4 cannabis cigarettes (27 mg THC) in unventilated room Multiple trials: no | Participant selection: NR Inclusion criteria for smokers: occasional (1 cigarette/wk) or moderate (1-3 cigarettes/wk) smoking Inclusion criteria for nonsmokers: NR | 8 smokers | All male, age 21-27 yr, height 5'9"-6'1" (1.75-1.85 m), weight 154-175 lbs (69.8-79.4 kg) | THC level in urine (EMIT) | 18 |
| 3 nonsmokers | NR | |||||
| Niedbala et al.,20 2005, United States | Intervention: participants were placed in severe second-hand smoke conditions in unventilated van for 1 h Multiple trials: 2 trials, each with 4 smokers and 4 passive inhalers; 5.4% THC in trial 1, 10.4% THC in trial 2 | Participant selection: volunteers; recruitment strategy NR Inclusion criteria for smokers: healthy white men who reported infrequent past cannabis use Inclusion criteria for nonsmokers: healthy white men who tested as cannabis-free before study based on oral fluid and urine tests and self-reported data | 8 smokers | 18-24 yr for both groups | THC level in oral fluid (Intercept collector pads) and urine | 16 |
| 8 nonsmokers | 34-50 yr in first group, 25-50 yr in second group | |||||
| Niedbala et al.,21 2004, United States | Intervention: smokers consumed 1 cannabis cigarette each (approximate THC level 1.75%) in presence of nonsmokers in sealed room Multiple trials: no | Participant selection: volunteers; recruitment strategy NR Inclusion criteria for smokers: healthy white men who reported infrequent prior use of cannabis Inclusion criteria for nonsmokers: healthy white men who tested as cannabis-free before start of study | 5 smokers | Age 21-25 yr | Air cannabinoid content, THC level in oral fluid and urine | 15 |
| 4 nonsmokers | Age 37-49 yr | |||||
| Perez-Reyes et al.,30 1983, United States | Intervention: smokers consumed cannabis cigarettes in presence of nonsmokers in a room (trials 1 and 3) and a car (trial 2); biological samples were then taken and compared between the 2 groups Multiple trials: 1) 2 cigarettes (2.5% and 2.8% THC), 2) 2 cigarettes (2.8% THC), 3) 4 cigarettes (2.8% THC) | Participant selection: NR Inclusion criteria for smokers: experienced marijuana users Inclusion criteria for nonsmokers: marijuana-naive participants | 6 smokers | 3 men, 3 women, "healthy and of normal weight and height in relation to their age and sex" | THC presence in air, THC level in urine (EMIT) and blood | 16 |
| 6 nonsmokers | 3 men, 3 women, "healthy and of normal weight and height in relation to their age and sex" | |||||
| Röhrich et al.,31 2010, Germany | Intervention: nonsmokers were exposed to marijuana smoke in Dutch coffee shop with ventilation (THC percentage NR) Multiple trials: no | Participant selection: NR Inclusion criteria for smokers: active smoker in coffee shop at time of experiment Inclusion criteria for nonsmokers: no history of cannabis use, no contact with cannabis in month preceding experiment | 8-25 smokers at a time | NR | THC level in blood and urine (gas chromatography-mass spectrometry) | 15 |
| 8 nonsmokers | 4 men, 4 women | |||||
| Zeidenberg et al.,32 1977, United States | Intervention: heavy marijuana smokers consumed cannabis (THC level NR) in presence of placebo smoker in locked ward Multiple trials: no | Participant selection: NR Inclusion criteria for smokers: NR Inclusion criteria for nonsmoker: NR | 5 smokers | NR | THC level in urine, subjective reporting, physical examination | 14 |
| 1 nonsmoker | NR |
Note: BMI = body mass index, EMIT = enzyme multiplied immunoassay technique, NR = not reported, SD = standard deviation, THC = tetrahydrocannabinol.
*Assessed with the use of the Downs and Black checklist,17 which rates papers on 5 constructs: 1) reporting, 2) external validity, 3) internal validity - bias, 4) internal validity - confounding and 5) power. A total score of 24-28 points = excellent, 19-23 points = good, 14-18 points = fair, less than 14 points = poor.18