Abstract
Background and Objectives:
To expand on epidemiologic studies examining associations between the legalization of recreational cannabis and use among young adults, we examined the associations between licensed and unlicensed cannabis outlet density and cannabis outcomes.
Methods:
A total of 1097 young adults aged 21 and older living in Los Angeles County were surveyed before licensed recreational cannabis outlets opened (Time 1: July to December 2017) and after (Time 2: July 2018 to June 2019). Using a database of open licensed and unlicensed cannabis retailers to calculate individual-level cannabis outlet density measures, we examined associations between outlet density within a 4-mile radius of participants’ residences with Time 2 outcomes of any past-month use, daily use, intentions to use, quantity used, consequences, and cannabis use disorder (CUD) symptoms.
Results:
After controlling for demographic factors and cannabis outcomes at a time point prior to their opening (Time 1), licensed cannabis outlets were associated with young adults’ cannabis use, heavy use, and intentions, and unlicensed outlets were associated with young adults’ heavy cannabis use and CUD symptoms.
Conclusion and Scientific Significance:
This study expands beyond studies of outlet prevalence to find that, after controlling for outcomes 1 year prior, licensed and unlicensed outlets were associated with young adults’ cannabis outcomes. The current study is among the first to find associations between cannabis use outcomes and density of cannabis outlets among young adults using data from two time points: preopening and postopening of recreational cannabis retailers. Findings can inform policies around the density and placement of cannabis outlets.
INTRODUCTION
Young adults are an at-risk group for heavy and problematic cannabis use. More than half of young adults initiate cannabis use by the age of 21,1 and heavy use in young adulthood can lead to subsequent physical and cognitive health problems.2 Trend studies have documented that prevalence rates for both cannabis use and cannabis use disorder (CUD) among young adults between the ages of 18 and 25 are rising in the United States, with those aged 21 to 25 reporting the heaviest use and most problems.3–6 Young adults aged 21 to 25 are twice as likely to report CUD compared with other age groups,4 and they are the least likely to pursue treatment for CUD.7 Given emerging laws and regulations in the United States that have made cannabis more accessible to young people, it is important to examine young adults’ use and problems in relation to changing policies, especially within the 11 states and the District of Columbia that have legalized possession and supply of recreational cannabis for those aged 21 and older.
Though researchers and policymakers have attempted to determine how legalization has affected cannabis outcomes among young people, thus far, studies have been largely based on examination of trends in cannabis use among adolescents from statewide or nationwide repeated cross-sectional surveys, and findings have been mixed.8–10 Few studies have looked at young adults; as one example, a study of college students from 587 US institutions in 48 states found a general trend toward increased rates of past-month cannabis use in states that had recreational cannabis laws compared with those that did not.11 With some exceptions, however, most studies do not factor in an essential component related to legalization: the emergence of cannabis outlets, which are retailers where individuals can legally purchase cannabis. Often, cannabis laws are passed months or years before regulations around the actual sale of cannabis are implemented, meaning that laws have been passed, but there are no retail outlets available for legal purchase. Thus, examinations of cannabis outcomes among young people post-legalization must factor in the availability of cannabis via these cannabis outlets.
Los Angeles (LA) County is an ideal location to study the effects of cannabis outlets on outcomes. LA County has a long-standing medical cannabis patient and dispensary program, starting in 1996 with more regulation by the state in 2003. The cultivation, possession, and sale of recreational cannabis for adults (age 21 and older) were passed by voter initiative in November 2016. On January 1, 2018, the state allowed recreational cannabis to be sold for nonmedical purposes at retail outlets after issuing licenses for cultivation, manufacturing, distribution, retail, and laboratory testing of the drug. Prior to this date, unregulated medical dispensaries flourished in California12; in 2016 and 2017, there were upwards of 900 medical cannabis dispensaries in LA County, yet there were no formal licensing procedures, and only 139 were in compliance with LA City’s business tax regulations.12,13 Legalization of recreational cannabis led to the conversion of many medical dispensaries to licensed retailers and sparked the regulation and closing of unlicensed medical dispensaries. The Bureau of Cannabis Control became the sole authority of licensing retailers. Although LA County implemented practices to locate and shut down unlicensed cannabis outlets starting January 1, 2018, unlicensed cannabis outlets remained prevalent. Our recent work identified 430 cannabis outlets operating in the county as of March 2019, of which only 38% were licensed.14
Researchers have begun to examine how the density of cannabis outlets around schools and residential addresses are associated with cannabis use,15–17 and how outlet locations are associated with the economic, neighborhood, and social environmental factors.18–21 However, this work has focused almost exclusively on medical cannabis dispensaries in a time prior to the opening of retail outlets. Moreover, very few studies have examined the effects of cannabis outlets longitudinally, and those that do have examined trends based on repeated cross-sectional surveys and have looked at adolescents and not individuals who actually have access to cannabis through legal purchase at retail outlets (ie, those aged 21 and older).22–24 Studies are needed to examine the unique contribution of cannabis outlets on young adult behavior during a period after cannabis was available through these outlets, while controlling for participants’ cannabis use behavior prior to availability of cannabis through these recreational outlets. Such data would allow for stronger conclusions about whether individuals’ cannabis outcomes are associated with the density of cannabis outlets.
The Present Study
This study used two time points to examine the associations between licensed and unlicensed cannabis outlets and cannabis outcomes among 1097 young adults from a period prior to the opening of recreational cannabis outlets to a period after recreational cannabis outlets were opened in LA County. Although medical dispensaries were available in the county for medical cannabis patients, there were no licensed recreational cannabis outlets prior to January 1, 2018, which represents the first time point in our data. We then assessed outcomes 1 year later during a period following the opening of recreational cannabis outlets (post-January 1, 2018), at which time many of the unregulated medical dispensaries were converted to retail outlets that sold both recreational and medical cannabis. Using a large-scale, multiwave online survey of young adults in LA County25–27 and a comprehensive database of licensed and unlicensed cannabis outlets operating in LA County at one point in time during Time 2 (May 2019),14 we examined whether the density of cannabis outlets by outlet licensure type (ie, licensed vs unlicensed) from individuals’ residential addresses was associated with cannabis outcomes of any past-month cannabis use, daily/near-daily cannabis use, intentions to use cannabis in the next 6 months, quantity of cannabis flower/bud used per occasion, consequences from use, and CUD symptoms. After controlling for outcomes assessed prior to the opening of retail outlets, we hypothesized that greater cannabis outlet density would be positively associated with cannabis outcomes. We explored the differential effects of licensed and unlicensed outlets given the wide availability of unlicensed outlets in LA County.14
METHODS
Participants and Procedures
Participants were initially recruited in 2008 from 16 middle schools in Southern California when they were in 6th and 7th grades for an evaluation of voluntary after-school alcohol and other drug prevention program.25 Since enrollment, they have completed 12 surveys assessing substance use. Details of the larger study, including participation and retention rates across waves, as well as details for how the sample was closely matched to larger nationally representative samples, are published elsewhere.26–28 Briefly, youth completed surveys about substance use behavior and attitudes initially during physical education classes and then moved to online surveys once they began high school. Retention rates for each survey ranged from 61% to 91% across all waves. We fielded the full sample at every wave so that all participants had an opportunity to participate in each survey.
For the current study, we began with 2277 participants who had completed the survey at Time 1 (wave 10 of the larger study) and restricted that sample to 1097 participants who (a) lived in LA County at Time 1 and Time 2 (excluding n = 358 from the original 2277), (b) were 21 years or older at Time 2 (excluding n = 75) to include only participants who had legal access to enter recreational outlets, and (c) completed the Time 1 survey before (July 1, 2017 to December 31, 2017) and Time 2 survey after (July 1, 2018 to June 1, 2019) the opening of recreational cannabis outlets (excluding n = 747). Participants completed the Time 1 and Time 2 surveys 1 year apart. The sample represented 44% of the larger cohort at Time 2 (1097/2497 of wave 11 participants), with no significant differences from the larger sample on demographics or any of the six included outcomes.
Density of Cannabis Outlets at Time 2
We used a multistep process to identify and geocode cannabis retailers in LA County. Methods are discussed briefly and described in detail elsewhere.14 First, we searched online cannabis outlets directories (ie, WeedMaps, Leafly) to create a database of both licensed and unlicensed cannabis outlets in LA County. We then verified address data and confirmed that each outlet was open for business through direct in-person observations of the outlet’s storefront. We confirmed whether each outlet was licensed or unlicensed to sell cannabis through a review of official online tools from the City of LA Department of Cannabis Regulation and the California Bureau of Cannabis Control. Procedures were completed in March 2019 and represented the 430 cannabis outlets open for business during the approximate time participants completed the Time 2 survey. Of these outlets, 162 were verified as licensed to sell cannabis and 268 were unlicensed (but operating). It was unclear for how long these outlets had been open at the time of data collection.
Addresses from the 1097 participants were used to calculate the average distance traveled (as the crow flies) over all times of the day and days of the week for a 10-minute (4 miles; range: 0–9 miles) time frame, based on the average driving distance in the United States for consumer goods being about 3.8 miles.29,30 As in our prior work,17 this 4-mile radius was calculated by drawing circular buffers around respondents’ home addresses and counting the number of licensed outlets within the mileage buffer. We created a similar measure of the density of unlicensed outlets. In a prior cross-sectional study of medical cannabis dispensaries, we examined the effects of outlets’ signage17 as an individual passing by an outlet may not know that cannabis is available inside in the absence of clear signage. Although we collected data on signage outside of the 430 cannabis outlets,14 there was extensive overlap between indicators of clear signage and licensed status, such that licensed outlets were more likely to have clear signage. Thus, presenting findings for indicators of clear signage would be redundant.
Measures
Outcomes
Three outcomes were assessed at both time points for all participants. Any past-month cannabis use was assessed using items from the Monitoring the Future study (1 = 0 days to 7 = 20–30 days), which was dichotomized to any past-month use vs no past-month use. Daily/near-daily cannabis use was determined by dichotomizing participants from the past-month use item who reported use on 20 to 30 days in the past month vs those who did not. Participants were asked if they had intentions to use cannabis in the next 6 months (1 = definitely no to 4 = definitely yes).31 An additional three outcomes were assessed among participants who reported any past-year use of cannabis using an item from the Monitoring the Future study (1 = none to 7 = 20 or more times) (n = 530). These participants were asked about the quantity of cannabis flower/bud used per occasion using an image depicting response options from 1 = “Less than 0.25 g” to 10 = “More than 5 g.” These responses were recoded to represent quantities in grams (eg, “between 1 and 1.5 g” recoded to 1.25 g) with a final range from 0.25 to 5 g. Those who did not use flower/bud were coded as 0. We focused on flower/bud given the popularity of this form of cannabis consumption over other forms. Participants also indicated how often in the past year (1 = never to 7 = 20 or more times) they experienced 10 cannabis use consequences (eg, less motivation to do things, relationships negatively impacted).32,33 The items were summed to create a composite score (α = .91). The Cannabis Use Disorders Short Form (CUDIT-SF)34 was used to assess for CUD symptoms over the past 6 months (not able to stop using marijuana/cannabis once they had started; devoted a great deal of their time to getting, using, or recovering from marijuana/cannabis; had a problem with their memory or concentration after using marijuana/cannabis); these items were rated 0 = never to 4 = daily or almost daily with a summary indicating a CUD severity score (α = .72).
Covariates
Participants reported on age, gender, race/ethnicity (Hispanic, non-Hispanic white, non-Hispanic black, non-Hispanic Asian, non-Hispanic other/multiracial), and college student status at Time 2 (not in college, in college part time, in college full time). Participants also reported their mother’s educational attainment, which served as a proxy for socioeconomic status.35 We controlled for neighborhood socioeconomic status using five census tract-level indicator variables from the American Community Survey36: median household income, level of education for the population 25 years and older, percent of population aged 16 and older that is unemployed, percent of households with children 18 years and younger that are female-headed, and percent of households below the federal poverty level. As in prior work,17 the index was calculated using the coefficients estimated from confirmatory factor analysis and merged using each participant’s census tract code. Neighborhood socioeconomic conditions have been correlated with both licensed and unlicensed retailers in California. Specifically, research has shown that the density of cannabis retailers is correlated with neighborhoods that have more people of color and greater poverty.37 We also included possession of a medical cannabis card at Time 1, which indicated whether the participant was enrolled in California’s medical marijuana program and served as an indicator of legal access to cannabis via dispensaries at Time 1. Time 1 outcomes were included to control for use and intentions in the prior year when retail outlets had not yet been open.
Analytic Plan
We conducted six models for each specified outcome at Time 2: any use, daily/near-daily use, and intentions to use for the entire sample, and quantity of cannabis flower used per occasion, cannabis consequences, and CUDIT-SF scores for those reporting past-year cannabis use. For continuous outcomes, we used traditional linear regression; for dichotomous outcomes, we used logistic regression. All models were estimated in R. Each model included covariates of corresponding Time 1 cannabis outcome and possession of a medical cannabis card at Time 1; Time 2 age, gender, race/ethnicity, college status, mother’s education, and neighborhood socioeconomic status. In each of the six models, we included both licensed and unlicensed cannabis outlets to examine their unique effects.
RESULTS
Sample Description
Table 1 includes demographics and descriptive statistics of cannabis outcomes, while Table 2 contains the estimates and confidence intervals for the six outcome models, including covariates. In each model, the Time 1 outcome was significantly positively associated with the Time 2 outcome.
TABLE 1.
Sample descriptives, information on cannabis outlets, and cannabis outcomes
| N = 1097 | ||
|---|---|---|
| Covariates | ||
| ● Age at Time 2, mean (SD) | 21.6 (0.6) | |
| ● Female gender, % (n) | 56.2 (617) | |
| ● Mother’s educational level, % (n) | ||
| ○ Did not finish high school | 14.0 (154) | |
| ○ Completed high school | 15.8 (173) | |
| ○ Completed some college | 14.1 (155) | |
| ○ Completed college or higher | 48.7 (534) | |
| ○Do not know | 7.4 (81) | |
| ● College student status at Time 2, % (n) | ||
| ○ Not currently in college | 35.1 (385) | |
| ○ In college part time | 13.8 (151) | |
| ○ In college full time | 51.1 (561) | |
| ● Race/ethnicity, % (n) | ||
| ○ Hispanic | 48.3 (530) | |
| ○ Non-Hispanic white | 17.5 (192) | |
| ○ Non-Hispanic black | 3.1 (34) | |
| ○ Non-Hispanic Asian | 19.6 (215) | |
| ○ Non-Hispanic other/multiracial | 11.5 (126) | |
| ● Medical cannabis card at Time 1, % (n) | 10.4 (105) | |
| Exposures: Cannabis outlets | ||
| ● Number of licensed cannabis outlets within 4 miles of individual’s home address, mean (SD) | 5.9 (4.8) | |
| ● Number of unlicensed cannabis outlets within 4 miles of individual’s home address, mean (SD) | 7.6 (6.5) | |
| Cannabis outcomes | Time 1 | Time 2 |
| Any past-month use of cannabis, % (n) | 30.0 (329) | 29.5 (324) |
| Any past-month daily or near-daily use of cannabis, % (n) | 8.0 (88) | 9.1 (100) |
| Intentions to use cannabis in the next 6 months (range, 1–4), mean (SD) | 2.1 (1.2) | 2.1 (1.2) |
| Quantity of cannabis flower/bud used per occassiona (range, 0–5), mean (SD) | 0.6 (0.8) | 0.7 (0.8) |
| Cannabis use consequencesa (range, 10–70), mean (SD) | 14.4 (7.6) | 15.1 (8.5) |
| CUD symptoms (CUDIT-SF score)a (range, 0–12), mean (SD) | 1.5 (2.2) | 1.8 (2.6) |
CUD = cannabis use disorder; CUDIT-SF = Cannabis Use Disorders Short Form.
Outcomes assessed and reported for participants reporting past-year use of cannabis. Mean age at Time 1 was 20.63, SD = 0.60.
TABLE 2.
Density of cannabis outlets within 4 miles and cannabis outcomes
| Standardized coefficients (95% confidence interval) |
||||||
|---|---|---|---|---|---|---|
| Any past-month cannabis use | Any past-month daily/near-daily cannabis use | Intention to use cannabis in next 6 months | Quantity of cannabis flower/bud used per occassiona | Cannabis use consequencesa | CUD symptoms (CUDIT-SF)a | |
| Cannabis outlets | ||||||
| ● Number of licensed cannabis outlets within 4 miles |
0.007 (0.002, 0.013) |
0.004 (0.001, 0.007) |
0.012 (0.001, 0.024) |
0.010 (−0.003, 0.022) |
0.095 (−0.039, 0.229) |
0.043 (−0.026, 0.112) |
| ● Number of unlicensed cannabis outlets within 4 miles | 0.000 (−0.005, 0.003) |
0.003 (0.000, 0.005) |
0.007 (−0.001, 0.016) |
0.010 (0.002, 0.019) |
0.036 (−0.054, 0.127) |
0.046 (0.004, 0.089) |
| Covariates | ||||||
| ● Cannabis outcome at Time 1 |
0.465 (0.409, 0.522) |
0.503 (0.443, 0.563) |
0.677 (0.621, 0.724) |
0.523 (0.448, 0.599) |
0.490 (0.413, 0.567) |
0.506 (0.356, 0.656) |
| ● Neighborhood SES | 0.027 (−0.006, 0.059) |
0.035 (0.015, 0.055) |
0.056 (−0.012, 0.124) |
−0.021 (−0.101, 0.059) |
−0.673 (−1.487, 0.141) |
0.251 (−0.160, 0.661) |
| ● Age | 0.002 (−0.039, 0.044) |
0.013 (−0.012, 0.038) |
−0.003 (−0.089, 0.084) |
−0.113 (−0.223, −0.003) |
−1.868 (−2.970, −0.767) |
−0.375 (−0.941, 0.190) |
| ● Hispanic race/ethnicityb | −0.031 (−0.104, 0.043) |
0.028 (−0.017, 0.073) |
−0.133 (−0.287, 0.021) |
0.109 (−0.059, 0.277) |
0.181 (−1.505, 1.867) |
0.950 (0.029, 1.872) |
| ● Asian race/ethnicityb | −0.059 (−0.138, 0.020) |
0.009 (−0.039, 0.057) |
−0.105 (−0.271, 0.061) |
0.045 (−0.164, 0.254) |
1.420 (−0.593, 3.434) |
0.505 (−0.579, 1.589) |
| ● Black/African-American race/ethnicityb | 0.043 (−0.103, 0.190) |
0.135 (0.046, 0.224) |
0.015 (−0.291, 0.321) |
0.093 (−0.242, 0.438) |
3.505 (0.203, 6.807) |
1.805 (0.290, 3.320) |
| ● Other race/ethnicityb | 0.052 (−0.038, 0.142) |
0.003 (−0.052, 0.058) |
0.131 (−0.059, 0.320) |
0.101 (−0.122, 0.325) |
1.603 (−0.567, 3.772) |
−0.137 (−1.301, 1.028) |
| ● Gender |
−0.057 (−0.102, −0.011) |
0.003 (−0.025, 0.030) |
−0.042 (−0.137, 0.053) |
−0.069 (−0.184, 0.047) |
−0.966 (−2.125, 0.194) |
−0.492 (−1.143, 0.160) |
| ● Mother graduated high schoolc | −0.073 (−0.154, 0.008) |
−0.024 (−0.073, 0.026) |
0.083 (−0.086, 0.252) |
0.112 (−0.101, 0.324) |
0.361 (−1.743, 2.465) |
0.525 (−0.647, 1.698) |
| ● Mother completed some collegec | −0.060 (−0.146, 0.026) |
−0.033 (−0.086, 0.019) |
0.084 (−0.096, 0.264) |
0.232 (0.022, 0.443) |
1.451 (−0.712, 3.613) |
0.632 (−0.549, 1.814) |
| ● Mother graduated collegec | −0.016 (−0.087, 0.055) |
−0.031 (−0.074, 0.012) |
0.066 (−0.082, 0.215) |
0.100 (−0.079, 0.279) |
1.056 (−0.811, 2.923) |
0.487 (−0.484, 1.459) |
| ● Part-time college studentd | −0.053 (−0.131, 0.024) |
−0.002 (−0.049, 0.045) |
0.148 (−0.013, 0.310) |
−0.047 (−0.151, 0.245) |
0.344 (−1.635, 2.324) |
−0.245 (−1.289, 0.797) |
| ● Full-time college studentd |
−0.055 (−0.109, −0.000) |
−0.010 (−0.044, 0.023) |
0.085 (−0.030, 0.200) |
−0.102 (−0.238, 0.034) |
−1.278 (−2.628, 0.071) |
−0.354 (−1.058, 0.350) |
| ● Medical marijuana card at Time 1 |
0.210 (0.124, 0.296) |
0.209 (0.154, 0.264) |
0.362 (0.184, 0.539) |
0.109 (−0.045, 0.263) |
1.505 (−0.022, 3.032) |
0.302 (−0.403, 1.007) |
These standardized coefficient estimates reflect change in log odds for the unit change in the indicated predictor. For example, the standardized coefficient of 0.003 for any past-month daily/near-daily cannabis use is the change in log odds for every additional outlet. Bolded values indicate statistically significant estimates with a P-value < .05.
CUD = cannabis use disorder; CUDIT-SF = Cannabis Use Disorders Short Form.
Outcome reported for participants who reported use of cannabis in the past year.
Non-Hispanic white as reference group.
Mother did not graduate high school as reference group.
Nonstudent status as reference group.
Cannabis Outlets Within 4 Miles
Any Past-Month Cannabis Use
A higher number of licensed cannabis outlets within 4 miles of home was significantly associated with a greater likelihood of past-month cannabis use after controlling for any use the prior year (odds ratio [OR] = 1.007 [confidence interval [CI]: 1.002, 1.013]). For each additional licensed cannabis outlet, there was an expected 0.7% increase in the odds of using cannabis in the past month. For example, there was an approximate 10% increase in the odds of using cannabis for someone with 14 licensed outlets within a 4-mile radius compared with someone with no outlets. The count of unlicensed cannabis outlets within 4 miles was not significantly associated with past-month use.
Any Daily/Near-Daily Past-Month Cannabis Use
Daily/near-daily use was significantly associated with the count of licensed cannabis outlets within 4 miles (OR = 1.004 [CI: 1.001, 1.007]), with a 0.4% increase in the odds of daily/near-daily use for each additional licensed outlet, and with the count of unlicensed cannabis outlets within 4 miles (OR = 1.003 [CI: 1.001, 1.005]) with a 0.3% increase in the odds of daily/near-daily use for each additional unlicensed outlet.
Intentions to Use Cannabis in the Next 6 Months
The count of licensed cannabis outlets within 4 miles was significantly associated with intentions to use (B = 0.012; SE = 0.006; t = 1.97, P = .049). The count of unlicensed cannabis outlets within 4 miles was not significantly associated with intentions.
Quantity of Cannabis Flower/Bud Used Per Occasion
Among those with past-year use, the number of unlicensed cannabis outlets within 4 miles was significantly associated with greater quantity consumed (B = 0.010; SE = 0.004; t = 2.384, P = .018). The number of licensed cannabis outlets was not significantly associated with the quantity of use.
Cannabis Use Consequences
Neither cannabis outlet density measure was significantly associated with cannabis use consequences among those who used cannabis in the past year.
CUD Symptoms (CUDIT-SF Scores)
Among those with past-year cannabis use, a higher count of unlicensed cannabis outlets within 4 miles was significantly associated with higher scores on the CUDIT-SF (B = 0.046; SE = 0.022; t = 2.13, P = .035). The count of licensed cannabis outlets was not significantly associated with the CUDIT-SF.
DISCUSSION
The current study used data across two time points to examine the associations between the density of cannabis outlets around young adults’ homes and their cannabis use, intentions to use, and consequences. Data were taken from two distinct time points, preopening and postopening of recreational cannabis retailers in LA County, and include an examination of both licensed and unlicensed cannabis outlets; the latter of which has been absent from most prior work. Findings mirrored prior cross-sectional studies showing associations between medical cannabis dispensaries and young adult cannabis outcomes,16,17,37,38 and generally indicated that the density of cannabis outlets around a 4-mile area of one’s residential address was associated with multiple cannabis outcomes. These associations between cannabis outlets and outcomes were observed during the first year of licensed cannabis retailers despite an already crowded market of unlicensed medical cannabis dispensaries in LA County in the year prior to the opening of licensed outlets.12,17,21 Yet, our findings were robust even after controlling for possession of a medical cannabis card during the year prior, which served as an indicator of access to cannabis from outlets at that time. Results were also robust even after controlling for sociodemographic characteristics at individual and neighborhood levels, as well as after controlling for individuals’ cannabis outcomes the year prior.
Findings varied by specific cannabis outcome and by cannabis retailer licensure status. For licensed outlets, higher density was significantly associated with an increased likelihood of past-month use, increased likelihood of past-month daily/near-daily use, and stronger intentions to use cannabis in the next 6 months. For unlicensed outlets, which made up 62% of all outlets at Time 2,14 higher density of outlets was significantly associated with an increased likelihood of past-month daily/near-daily use, and for those with past-year use, greater quantity consumed, and more symptoms of CUD. Of note, the density of outlets was not significantly associated with consequences, perhaps because the measure focused more on social and relational effects of cannabis use than the symptoms of CUD assessed by the CUDIT-SF.
The mechanisms through which licensed and unlicensed outlets affect outcomes are not entirely clear and an area for future research, but for those young adults reporting past-year use, we found the density of unlicensed retailers was significantly associated with heavier use (ie, greater quantity used per occasion) and CUD symptoms, whereas licensed outlets were not. Unlicensed retailers are illegal and do not abide by licensing requirements that prohibit the sale of cannabis products from unlicensed producers or that restrict minors from entering the store and purchasing products, paying sales tax, and limiting the amount of cannabis that can be purchased by an adult each day. Young adults who use cannabis more frequently may be drawn to purchasing from unlicensed shops because of discounted prices and lack of regulation on purchase quantities. Unlicensed products, which do not abide by packaging and testing regulations, may also contain harmful contaminants and misrepresent product potency. In other work, young adults who reported the use of high-potency cannabis products also reported higher CUDIT scores and risk of dependence compared with those who used less potent cannabis products.39 Thus, the efforts to regulate unlicensed retailers and reduce the density of cannabis retailers may be important factors to be considered when implementing strategies to mitigate potential public health harms from expanded legal access to cannabis.
Limitations
By design, we looked at the effects of cannabis outlets on those who were legally able to purchase cannabis from outlets at Time 2; thus, our sample is restricted to those who were 21 years old at Time 2, which limits the generalizability to other young adults. Although it is a strength of the study that we have Time 1 outcomes prior to the opening of licensed cannabis outlets for participants, we may be modeling the novelty effects of a new legal market. In future work, we can monitor changes in cannabis behavior in subsequent waves. Moreover, Time 1 and Time 2 assessments were 1 year apart, and although most participants completed their Time 2 survey between November 2018 and April 2019, our cannabis outlets database represented the open outlets during March 2019, which is the time period we collected the outlet data. We were unable to look at the exact number of open outlets for each participant at the time they completed their Time 2 survey.
Also, we do not have direct data on whether young adults in our sample purchased cannabis from retail outlets (eg, they could have been given cannabis from a friend) or what retailer they purchased cannabis from. Although we attempted to control for this by including Time 1 outcomes in models, it is also possible that recreational outlets emerged in areas that already had higher cannabis use; presumably, retailers targeted areas where more customers would live. Future studies should test if associations hold among young adults who report purchasing cannabis from retailers and examine how opening retail cannabis outlets has changed modes of cannabis use and product preferences—particularly given some of the newer high-potency products that are of public health concern.9 In addition, we examined one county in a state with laws for legalized recreational cannabis and with a large number of licensed and unlicensed cannabis outlets. Future studies will need to determine if effects are similar in other states with varying laws, as well as in different municipalities throughout California, where laws for cannabis outlets may differ. Finally, although the effects reported here are compelling, especially considering the number of covariates included, effect sizes are small. Continued longitudinal research is needed to better understand the short- and long-term effects of recreational cannabis legalization.
CONCLUSIONS
Findings indicate that among young adults aged 21 and older in LA County, a higher density of both licensed and unlicensed cannabis outlets near young adults’ homes was associated with greater likelihood of use, heavier use, stronger intentions to use, and more problematic use during a period after the opening of recreational cannabis outlets. Regulations for licensed outlets, as well as greater enforcement of penalties for unlicensed cannabis outlets, may be needed. Beyond increased legal access to cannabis, there are possibly indirect effects associated with changes in cannabis outcomes among young adults, such as increased perceptions of the acceptability of cannabis use and effects from outlets’ advertising (eg, on freeway billboards). Complementary studies should use longitudinal approaches to examine how cannabis outlet density also affects underage use.
Footnotes
Declaration of Interest
Authors have no conflicts of interest to report. This research has not been previously published, either in whole or in part, nor have the findings been posted online. As the corresponding author, I confirm my full access to all aspects of this research and writing process, and I take final responsibility for this paper.
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