Table 1.
Studies investigating the role of recreational cannabis legalization on cannabis and other substance consumption.
| Author | Year | Location | Date of legalization | Study design | Sample | Brief findings |
|---|---|---|---|---|---|---|
| Cannabis use in adolescents | ||||||
| Duan et al | 2022 | U.S. | Longitudinal | N = 19 503 | In states with RCL adolescents who never used cannabis but used e-cigarettes were more likely to use cannabis than those living in states without recreational cannabis legalization. | |
| Estoup et al | 2016 | Washington | 2012 | Cohort | N = 262 | Cannabis-related consequences significantly increased following RCL. There was not a significant effect of frequency of cannabis use. |
| Gunadi et al | 2022 | U.S. | 2016 | Longitudinal | N = 21 863 | Significant association between RCL and transition from non-users to cannabis users when compared to states with no medical or recreational cannabis legalization and states with no legalization combined with those with medical cannabis legalization, but not when compared to states with medical cannabis legalization only. |
| Mason et al | 2016 | Washington | 2012 | Cohort | N = 238 | RCL cohort had increased cannabis use at follow-up compared to pre-RCL, but this increase was not significant. There were positive, but not significant, cohort effects for cannabis use. |
| Paschall et al | 2022 | California | 2016 | Repeated cross-sectional | N = 3 319 329 | Adolescent alcohol and cannabis co-users had a significant increase in the frequency of past 30-day cannabis use following RCL. |
| Rusby et al | 2018 | Oregon | 2015 | Cohort | N = 444 | RCL cohort was more likely to increase their intent to use cannabis overtime, while the pre-RCL cohort was less likely to increase willingness and intent to use. RCL was not associated with initiating cannabis use. The RCL cohort did have significant increases in cannabis use compared to pre-RCL. |
| Stormshak et al | 2019 | U.S. | Cohort | N = 1438 | Post-RCL cohort had higher odds of cannabis use compared to the pre-RCL cohort over time. Use decreased over time for pre-RCL but increased post-RCL. However, patterns of use were similar in cohorts. | |
| Vignault et al | 2021 | Quebec | 2018 | Archival administrative data | N = 2615 | No significant increase in the frequency of or prevalence of cannabis use following RCL. |
| Yu et al | 2020 | U.S. | Cohort | N = 749 152 | RCL was not significantly associated with period effects for cannabis use, but medical legalization was. | |
| Zuckermann et al | 2021 | Canada | 2018 | Repeated cross-sectional | N = 102 685 | Adolescents had increased odds of ever using cannabis in the year following RCL in the cross-sectional data 28 . However, the longitudinal sample revealed no significant differences in the odds of ever use, current use, and regular use of cannabis post-RCL. |
| Cannabis use in young adults | ||||||
| Bailey et al | 2020 | Washington | 2012 | Longitudinal | N = 281 | RCL predicted a higher likelihood of past-year cannabis use. |
| Barker & Moreno | 2021 | Washington & Wisconsin | 2012 | Longitudinal cohort | N = 338 | Significant association between RCL and increased cannabis use. The rate of students ever using cannabis did not change, however, in those who had used cannabis prior to RCL, the proportion of students using in the past 28-days increased faster following RCL in Washington (legal-state) when compared with the rate of increase in Wisconsin (non-legal state). |
| Han & Seo | 2022 | U.S. | Longitudinal cohort | N = 6155 | In a sample of young adults who had never vaped cannabis at the time of recruitment results revealed that cannabis use in the past year did not differ in states with or without RCL, although, those living in states with RCL did show a larger increase in rates of cannabis vaping across time, compared to those in non-RCL states. | |
| Kerr et al | 2017 | Oregon | 2015 | Repeated cross-sectional | N = 10 924 | Rates of cannabis use significantly increased following RCL but use also increased over time in non-legal states. Oregon students with heavy alcohol use had greater increases in recent use. Among heavy drinker’s RCL had a greater impact on cannabis use for minors. No support that first year students experience a greater effect of RCL on use. RCL was not associated with changes in cigarette and alcohol use. |
| Cannabis use in adults | ||||||
| Gali et al | 2021 | California | 2016 | Longitudinal cohort | N = 429 | Past 30-day cannabis use increased significantly 1-month post-RCL and remained elevated 6-months post-RCL. |
| Gunadi et al | 2022 | U.S. | 2016 | Longitudinal cohort | N = 21, 863 | In adults, there was an association between legalization and transition from non-users to cannabis users and non-users to weekly users when compared to states with no medical or recreational cannabis legalization and states with no legalization combined with those with medical cannabis legalization. |
| Kerr et al | 2018 | U.S. | 2018 | Repeated cross-sectional | N = 37 359 | There was a non-significant increase in cannabis use post-RCL. Rates of simultaneous cannabis and alcohol use did not increase with RCL. Comparison studies found evidence of some increase in cannabis use 12 months after RCL. Past year cannabis use rates started increasing prior to RCL. |
| Turna et al | 2021 | Ontario | 2018 | Longitudinal | N = 1502 | For non-users prior to RCL, there were significant increases in cannabis use frequency, quantity of cannabis used, and severity of cannabis misuse following RCL. The opposite pattern was seen for those reporting cannabis use prior to RCL, with significant decreases in frequency of use, quantity, and misuse. |
| Vignault et al | 2021 | Quebec | 2018 | Archival administrative data | N = 2615 | No significant increase in the frequency of or prevalence of cannabis use following RCL. |
| Cannabis use in clinical populations | ||||||
| Geoffrion et al | 2021 | British Columbia | 2018 | Archival administrative data | N = 3705 | Cannabis use rates increased from pre- to post-RCL for women with pelvic pain. |
| Grigorian et al | 2019 | California | 2016 | Archival administrative data | N = 21 173 | The rate of adult positive THC screens increased post-RCL. Pediatric positive THC screens were non-significant. |
| Hawke & Henderson | 2021 | Ontario | 2018 | Cohort | N = 269 | In a sample of youth in an outpatient addictions treatment program, there was no change in the rate of cannabis use following RCL. |
| Hawley et al | 2019 | British Columbia | 2018 | Repeated cross-sectional | N = 1673 | There was a significant increase in the prevalence of current cannabis use after RCL among cancer patients. |
| Pusateri et al | 2022 | Colorado & Washington | 2012 | Archival administrative data | N = 18 545 | There was a significant increase of irritable bowel disease patients reporting cannabis use post-RCL. |
| Rosic et al | 2021 | Ontario | 2018 | Repeated cross-sectional | N = 1390 | In individuals receiving treatment for opioid use disorder, cannabis use was compared for those recruited 6 months before or after RCL with no significant changes in the prevalence or frequency of self-reported or urine screen-detected cannabis use following RCL. |
| Maternal cannabis use | ||||||
| Grant et al | 2018 | Washington | 2012 | Cohort | N = 1359 | Increases in cannabis use in mothers who used substances during pregnancy at treatment exit post-RCL. Post-RCL cohort more likely to report cannabis use 30 days following exit compared to pre-RCL-cohort. Post-RCL cohort also less likely to quit cannabis use and more likely to have used from enrollment to exit. Post-RCL cohort who initiated use during treatment used about 3x more than Pre-RCL cohort. |
| Lee et al | 2022 | California | 2016 | Cohort | N = 466 | Urine screen-detected cannabis use during pregnancy increased from 6% to 11% following RCL. |
| Yee et al | 2021 | U.S. | Cohort | N = 2926 | No significant difference in cannabis or alcohol use associated with RCL in women living with HIV during pregnancy or the postpartum period. | |
| Other substance use | ||||||
| Bailey et al | 2020 | Washington | 2012 | Longitudinal | N = 281 | RCL predicted a higher likelihood of alcohol use. RCL was not significantly associated with past-year cigarette use. |
| Grigorian et al | 2019 | California | 2016 | Archival administrative data | N = 21 173 | There was no difference for alcohol and other drug screens in adults post-RCL. Post-RCL there was increased rate of benzodiazepine and barbiturate screens for pediatrics. |
| Hawke & Henderson | 2021 | Ontario | 2018 | Cohort | N = 269 | No significant effect of RCL on rates of alcohol or illicit drug use. |
| Kerr et al | 2017 | Oregon | 2015 | Repeated cross-sectional | N = 10 924 | Among heavy drinker’s RCL had a greater impact on cannabis use for minors. RCL was not associated with changes in cigarette and alcohol use. |
| Mason et al | 2016 | Washington | 2012 | Cohort | N = 238 | The pre-RCL cohort had higher past month cigarette use at follow-up compared to the RCL cohort. Alcohol use was also greater for the pre-RCL cohort but not significantly. There were negative and significant cohort effects for alcohol and cigarette use. |
| Paschall et al | 2022 | California | 2016 | Repeated cross-sectional | N = 3 319 329 | Among 7th, 9th, and 11th grade students in the U.S., RCL was associated with a 6% increase in the odds of past 30-day alcohol and cannabis co-use. The association was even stronger in students with past 30-day alcohol use and heavy drinking. However, among past 30-day cannabis users, RCL was associated with a 24% reduction in co-use. |
| Route of administration | ||||||
| Gali et al | 2021 | California | 2016 | Longitudinal cohort | N = 429 | Smoking, vaping, and edibles (in that order) were the most frequent modes of cannabis use pre- and post-RCL. The least common mode of cannabis use was blunts, which declined following RCL. |
| Zuckerman et al | 2021 | Canada | 2018 | Cohort | N = 2953 | Changes in the number of different modes of cannabis use reported by high school students showed that 31.3% of students maintained a single mode of use, 14.3% maintained multiple modes of use, 42.3% expanded and 12.1% reduced their modes of use pre- and post-RCL. |
Author, author of article; Year, publication year of article; Location, jurisdiction article data was collected in; Date of Legalization, year legalization was enacted in jurisdiction; Sample, total N of article sample; RCL, Recreational Cannabis Legalization.