ABSTRACT
Background: In 2016, California transitioned from legalized medical cannabis use to adult-use. Little is known about how this policy change affected medicinal cannabis use among young adults.
Objectives: To identify longitudinal groups of medicinal cannabis users and concurrent changes in health- and cannabis use-related characteristics among young adults in Los Angeles between 2014 and 2021.
Methods: Cannabis users (210 patients and 156 non-patients; 34% female; ages 18–26 at baseline) were surveyed annually across six waves. Longitudinal latent class analysis derived groups from two factors – cannabis patient status and self-reported medicinal use. Trajectories of health symptoms, cannabis use motives, and cannabis use (daily/near daily use, concentrate use, and problematic use) were estimated across groups.
Results: Three longitudinal latent classes emerged: Recreational Users (39.3%) – low self-reported medicinal use and low-to-decreasing patient status; Recreational Patients (40.4%) – low self-reported medicinal use and high-to-decreasing patient status; Medicinal Patients (20.3%) – high self-reported medicinal use and high-to-decreasing patient status. At baseline, Medicinal Patients had higher levels of physical health symptoms and motives than recreational groups (p < .05); both patient groups reported higher level of daily/near daily and concentrate use (p < .01). Over time, mental health symptoms increased in recreational groups (p < .05) and problematic cannabis use increased among Recreational Patients (p < .01).
Conclusions: During the transition to legalized adult-use, patterns of medicinal cannabis use varied among young adults. Clinicians should monitor increases in mental health symptoms and cannabis-related problems among young adults who report recreational – but not medicinal – cannabis use.
Introduction
California became the first U.S. state to legalize the use of cannabis for medical purposes in 1996. Adult-use cannabis was legalized in CA 20 years later in 2016 and retail cannabis sales started on January 1, 2018 (Citation1). The enactment of the law created new opportunities for young adults, a group with already the highest level of cannabis use in the U.S (Citation2) to legally access cannabis for adult use. Greater cannabis use in states where adult-use is legal (Citation3) has raised public health concerns due to potential downstream effects (Citation4), though evidence that legalization increases consumption among young adults is mixed (Citation5–8). Surprisingly, transition from medical-only to adult-use policy environments has received limited attention despite the fact that adult-use legalization diminishes the impetus to participate in medical cannabis programs. Indeed, a recent assessment of U.S. medical cannabis licensure reported that between 2016 and 2020, patient enrollment increased in medical-only states yet decreased in 5 of 7 adult-use states, including Colorado, Oregon, Alaska, Michigan, and Nevada (Citation9). In our past work (Citation10), we found that a higher proportion of young adults transitioned from patients to non-patients rather than the reverse in the period immediately following adult-use legalization in California. Little is known, however, how adult-use legalization affects cannabis patient status among young adults in the longer term.
Patient status alone offers a limited understanding of medicinal cannabis use since state-approved qualifying conditions do not uniformly coincide with medicinal intent among cannabis users (Citation11). Furthermore, since some people seek a doctor’s recommendation for legal access (Citation12,Citation13) or legal protection (Citation12,Citation14,Citation15), it is important to assess self-reported medicinal cannabis use, which is common (Citation16,Citation17). For instance, among people aged 16–65, 27% reported lifetime medicinal cannabis use with the highest prevalence among 25–31-year-olds in states with adult-use cannabis according to a 2018 population survey (Citation18). AminiLari et al. (Citation19), the only longitudinal study to assess the effects of adult-use legalization on self-reported medicinal use, documented that six months after legalization, a notable proportion of 254 Canadian adults, aged 19 to 66, who had previously used cannabis for medicinal purposes, shifted to either dual medicinal/recreational or exclusively recreational use. However, no research has documented changes in self-reported medicinal cannabis use among young adults. Furthermore, evidence is limited regarding the interplay between doctor-recommended and self-reported medicinal use during transitions to adult-use cannabis.
Mild to chronic health conditions are associated with medicinal cannabis use (Citation20,Citation21), which highlights the relevance of longitudinally assessing concurrent changes in health symptoms alongside changes in medicinal use. Our previous work showed that psychological problems (i.e., insomnia, anxiety, and depression) and pain were the most common lifetime health conditions among young adult cannabis users with prevalence higher among patients than non-patients (Citation12). To date, only a few longitudinal studies have assessed changes in health among people who use cannabis for medicinal purposes. For instance, Meng et al. (Citation22) followed a cohort of adult cannabis patients with chronic pain and observed improvements in pain, quality of life and general health yet found no changes in anxiety or stress. Schlienz et al. (Citation23) documented improvements in sleep, pain, anxiety, depression, and quality of life in a cohort of medicinal cannabis users, including children and adults with diagnosed health conditions. Less is known about long-term changes in health associated with medicinal cannabis use among young adults.
Medicinal cannabis use is also characterized by specific health-related reasons or motives for use. Young adults commonly use cannabis for sleep, pain, and mental health problems, especially anxiety (Citation12,Citation18,Citation24). Research has demonstrated that health-related motives are often aligned with clinical concerns in this age group. For instance, pain relief was found to be the primary cannabis use motive among young adults who met criteria for chronic pain (Citation25). Sleep motives (Citation26) and coping motives – using cannabis to cope with emotional distress (Citation26,Citation27) – were linked to anxiety and depressive symptoms among emerging adults. However, changes in health-related motives between young adults who use cannabis for medicinal and recreational purposes remain largely unexplored.
To address these knowledge gaps, the present study examined a cohort of young adults, including both cannabis patients and non-patients, recruited in Los Angeles between 2014 and 2015 and followed through 2020–2021, i.e., from pre- to post-legalization of adult-use cannabis in California. We sought to identify patterns of medicinal cannabis use based on two characteristics – medical cannabis patient status and self-reported medicinal cannabis use – since they represent complimentary but distinct dimensions of medicinal cannabis use and how those patterns differ by demographic characteristics. Then, we assessed concurrent changes in health symptoms and health-related use motives across patterns of medicinal cannabis use. Additionally, given that adult-use legalization is linked with greater cannabis consumption (Citation3,Citation5) and that it increases access to high-potency cannabis products (Citation28,Citation29) associated with adverse health outcomes (Citation30), we evaluated concurrent changes in cannabis use, including daily/near daily use, use of cannabis concentrates, and problematic cannabis use among longitudinal groups. Our overarching aim was to determine how medicinal cannabis use and its potential correlates changed among young adults during California’s transition to an adult-use legal cannabis environment.
Methods
Participants
Data for this analysis comes from the Cannabis, Health, and Young Adults (CHAYA) project, a prospective cohort study which examined cannabis use among 366 young adults recruited in Los Angeles between 2014 and 2015 (Citation12,Citation31). The recruitment criteria at baseline included age (18–26 years old), using cannabis at least 4 times in the past 90 days, living in the Los Angeles metropolitan area, and ability to read and speak English. Additionally, participants had to either 1) possess a valid medical cannabis recommendation or 2) have no history of possessing a medical cannabis recommendation. The cohort has been surveyed annually and the present analysis utilized data from the first six waves collected through 2020–2021. Participants were surveyed face-to-face between Waves 1–3, and remotely via a Research Electronic Data Capture survey link for Waves 4–6. Importantly, by January 2018, when the recreational cannabis sales had begun in California, most participants had turned 21, i.e., became eligible for adult-use cannabis purchases. The study was approved by the Institutional Review Board at Children’s Hospital Los Angeles. The participants provided voluntary consent to participate in the study.
Measures
Medical cannabis patient status was determined by the participant’s possession of a current medical cannabis recommendation (i.e., yes/no), verified by interviewers in Waves 1–3 of data collection by visual inspection of a hard or electronic copy of the recommendation either before or after survey administration. Patient status was assessed via self-report for Waves 4–6 when the survey was moved to the online format.
Self-reported medicinal cannabis use was measured by a question asking to distinguish between recreational and medicinal cannabis use in the past 90 days. Medicinal use was explained as using cannabis “to treat or help cope with any physical ailments, such as pain or discomfort, or psychological conditions, such as feeling anxious or sad, insomnia, etc.” The question was measured by a 5-item Likert-type scale ranging from “exclusively medical (no recreational uses)” to “exclusively recreational (no medical uses).” Consistent with our prior work (Citation10,Citation32), response options were dichotomized into “self-reported medicinal use” (collapsing “exclusively medical” and “primarily medical” categories) and “self-reported recreational use” (collapsing “equally medical and recreational,” “primarily recreational,” and “exclusively recreational” categories).
Demographic characteristics. Participants were asked to self-report several demographic characteristics, including age, sex assigned at birth (female/male), Hispanic ethnicity, and age of cannabis use initiation.
Health symptoms. General psychological distress was measured by the Brief Symptom Inventory-18 (BSI-18; Citation33), which includes three six-item scales (anxiety, depression, somatization) and the overall Global Severity Index (GSI). Raw scores are converted into T-scores, with higher scores indicating higher levels of psychological distress and scores ≥ 63 on GSI or two scales indicating clinical significance. Current non-minor pain was measured by a yes/no screening question from the Brief Pain Inventory-Short Form (Citation34), i.e., “Throughout our lives, most of us have had pain from time to time (such as minor headaches, sprains, and toothaches); Have you had pain other than these everyday kinds of pain today?.”
Motives for cannabis use were examined by utilizing a modified version of the Comprehensive Marijuana Motives Questionnaire (CMMQ; Citation35). The original 36-item measure assessed 12 three-item subscales for cannabis use motives, asking participants to think of all times they used marijuana and rate the frequency of using each item on a scale from 1 (“almost never/never”) to 5 (“almost always/always”). We extended the scale to include three additional health-related subscales (pain-, focus-, and attention-related motives), and the adapted measure demonstrated good-to-acceptable fit (Citation36,Citation37). In the present study, three motives subscales were examined based on their theoretical relevance and reported associations with at least three common health conditions among young adult cannabis users: pain (e.g., using “to relieve aches and pains”), sleep (e.g., “to help you sleep”), and coping with emotional distress (e.g., “to forget your problems”).
Cannabis use variables included daily/near daily cannabis use, concentrate use, and problematic cannabis use. The number of cannabis use days in the past 90 days was dichotomized into “daily/near daily use” if frequency of use ranged between 60–90 days (i.e., 5–7 days a week) and “other use,” i.e., below that threshold. Concentrate use was assessed by a yes/no question asking about any 90-day use of “concentrates, e.g., wax, shatter, dab.” Problematic cannabis use was measured by the Severity of Dependence Scale (SDS; Citation38), a 5-item validated instrument assessing participants’ worries and concerns about their cannabis use. The total score is the sum of all items, with a cutoff score of 4 indicating dependence (Citation39,Citation40).
Analysis
Initially, all longitudinal variables were examined in the total sample across all waves using SPSS (version 28). Retention and attrition within subsamples were calculated by comparing variables of interest (demographics, health symptoms, use motives, and cannabis use) during three periods of observation: Waves 1–6, Waves 1–3, and Waves 4–6. Then, longitudinal groups of medicinal cannabis users were derived using longitudinal latent class analysis (LLCA) in MPlus (version 8.8). LLCA is a longitudinal person-centered approach that identifies unobserved groups of people with similar patterns of responses over time (Citation41). LLCA is a mixture model, but unlike growth mixture models, LLCA models patterns of states across time rather than scaled growth (Citation41). In the present study, LLCA estimated joint probabilities of two repeatedly measured binary variables: cannabis patient status and self-reported medicinal cannabis use. Based on our prior assessment (Citation10), as well as drastic decreases in the proportions of medical cannabis patients by the end of the study, we determined that patient-related transitions are largely one-directional, i.e., from patients to non-patients. Therefore, rather than focusing on transitions between specific time points and employing latent transition analysis, we opted for LLCA to identify the overarching patterns of medicinal cannabis use from pre- to post-legalization across all time points. Missing data were handled with the full information maximum likelihood estimator with robust standard errors utilized by MPlus.
The number of classes was determined based on an unconditional (i.e., without covariates) model (Citation42). Models with varying number of latent classes were compared using several relative fit criteria: Akaike Information Criterion (AIC), Bayesian Information Criterion (BIC), sample size-adjusted BIC (sBIC), the Vuong-Lo-Mendell-Rubin (VLMR) test, Lo-Mendell-Rubin (LMR) test, and the bootstrapped likelihood ratio test (BLRT). Lower values for AIC, BIC, and sBIC indicate better model fit compared to other models, and significant p-values for VLRM, LMR, and BLRT tests indicate better model fit for a model with k+1 versus a model with k classes. We also considered a minimal class size and interpretability of each model. While we reviewed entropy (i.e., degree of homogeneity between classes with values closer to 1 indicating better class separation), it was not used to determine the number of classes as recommended (Citation43). Another classification measure – average class posterior probabilities (values ranging from 0.8 and higher deem acceptable; Citation44) – was evaluated as well.
Once the final model with the optimal number of classes was identified, the manual 3-step approach in MPlus (Citation45,Citation46) was employed to assess the associations of latent classes with covariates and estimate concurrent changes in longitudinal characteristics across classes. Classes were preserved in the 3rd step by utilizing a modal class assignment variable and class-specific threshold values obtained from the unconditional LLCA model in the previous steps. The effect of demographic characteristics on latent class membership was estimated by regressing the latent class variable on the covariates using multinomial logistic regression. Due to the exploratory nature of this research, only time-invariant covariates were tested, including baseline age, female sex, Hispanic ethnicity, and age of cannabis use initiation. Then, we modeled trajectories for health symptoms, motives, and cannabis use across “known” latent classes, estimating means of the growth factors (i.e., intercepts and slopes) conditional on latent class membership. The growth models retained the covariates as latent class predictors. Significant differences between classes were tested by comparing growth factor means using Z-test for class pairwise comparisons and Wald chi-square test for overall comparison.
Results
Baseline and longitudinal characteristics of the total sample
Baseline characteristics
The baseline sample included 210 medical cannabis patients and 156 non-patients, and on average was 21.2 years-old (SD = 2.5), 34% female, and 45.1% ethnically Hispanic. The average age of cannabis use initiation was 15.2 years (SD = 2.3) (). Among cannabis patients, the most common primary health conditions reported to a doctor to receive the medical recommendation included sleep, mood, or other psychiatric condition (53.8%), followed by chronic pain or discomfort (20.5%) and spinal/musculoskeletal conditions (14.8%).
Table 1. Sample characteristics of key variables of interest from Wave 1 to Wave 6.
Longitudinal characteristics
Between baseline and Wave 6, the overall sample size decreased by 31.4%; attrition was marginally associated with male sex (p < .1). Between Waves 1–3, attrition and retention subsamples were not significantly different, and between Waves 4–6, attrition was associated with the lower level of pain motives (p < .01) (Supplemental Table S1).
While the proportion of cannabis patients decreased from 57.4% at baseline to 6% at Wave 6, the level of self-reported medicinal use remained largely unchanged (24.3% at baseline, 23.8% at Wave 6). Between Waves 1–6, the level of psychological distress (i.e., BSI scale scores) and problematic cannabis use increased, while the level of current pain, all use motives, daily/near daily cannabis use, and concentrate use decreased ().
Enumeration of longitudinal latent classes
Longitudinal latent class analysis was performed with the number of classes varying from one to five (). Adding a class to each subsequent model resulted in more favorable relative fit indices through the 3-class model. While the 2-class solution had better entropy among all models, the average class posterior probabilities for the 3-class model were acceptable (>.8) and the 3-class solution added a nuance of having a group with a distinct longitudinal pattern of medicinal use. Based on the interpretability as an additional consideration, a 3-class model was selected for further analysis.
Table 2. Model fit indices for longitudinal latent class analysis.
Characteristics and predictors of latent classes
shows estimated probabilities of two medicinal use characteristics across each class and Supplemental Table S2 provides 95% bootstrap confidence intervals around the probabilities. Class 1 (39.3%, n = 144), labeled Recreational Users, was characterized by low-to-decreasing (i.e., .219 to .039) probability of cannabis patient status and low (<.3) probability of self-reported medicinal use over time. Class 2 (40.4%, n = 148), labeled Recreational Patients, represented participants with a high-to-decreasing (.779 to .036) probability of maintaining cannabis patient status and a very low (<.1) probability of self-reported medicinal use. Class 3, labeled Medicinal Patients, represented about one-fifth of the sample (20.3%, n = 74). Similar to Class 2, this group was marked by high-to-decreasing (.852 to .150) probability of cannabis patient status. Unlike the other groups, however, this class had a consistently higher (>.5) probability of self-reported medicinal use over time. Additionally, an alternate LLCA estimated for sensitivity purposes – dichotomizing “self-reported medicinal use” into “any medicinal use” versus “primarily/exclusively recreational use” – indicated that the original LLCA yielded more meaningful patterns of longitudinal medicinal use (refer to the Supplemental Note along with Supplemental Tables S4 and S5 for details).
Figure 1. Longitudinal patterns of medicinal cannabis use from the selected 3-class model: Recreational Users (39.3% of the sample; low self-reported medicinal use and low-to-decreasing patient status), Recreational Patients (40.4%; low self-reported medicinal use and high-to-decreasing patient status), and Medicinal Patients (20.3%; high self-reported medicinal use and high-to-decreasing patient status). Y-axis displays the estimated probabilities of patient status and self-reported medicinal cannabis use in each class. Descriptively, findings show that patient status decreased but self-reported medicinal cannabis use remained steady in each class. W1-W6 = Waves of data collection. Four-digit year notations represent dates of data collection within each wave.
Next, we examined the effect of covariates on membership in longitudinal latent classes (). In a model simultaneously accounting for age, female sex, Hispanic ethnicity, and age of cannabis use initiation, older participants had higher odds of membership in Medicinal Patients versus Recreational Users (AOR 1.16, 95%CI: 1.01, 1.32). Female sex was associated with lower odds of belonging to Recreational Patients than Recreational Users (AOR 0.42, 95%CI: 0.21, 0.82). Hispanic ethnicity or age of cannabis use initiation did not predict membership in the longitudinal classes.
Table 3. The association of longitudinal latent classes with covariates.
Trajectories of health symptoms, use motives, and cannabis use across latent classes
Health symptoms
There were no significant differences between the classes on overall psychological distress, BSI-Anxiety, or BSI-Depression with respect to either intercept or slope (). Medicinal Patients had a higher initial BSI-Somatization score than the recreational groups based on the pairwise test (omnibus Wald test was not significant). Over time, BSI-Depression increased in both recreational groups and BSI-Anxiety increased among Recreational Users, though the scores did not cross a clinical cutoff level. Compared to the recreational groups, Medicinal Patients had higher initial level of current pain. Over time pain symptoms decreased in Recreational Patients only ().
Table 4. Estimated trajectories of health symptoms, cannabis use motives, and cannabis use across longitudinal latent classes.
Cannabis use motives
As indicated by significant differences in the intercepts (), Medicinal Patients had a higher baseline mean of sleep and pain motives than the recreational groups. Over time, all classes experienced reductions in sleep and pain motives, though differences in the rate of change, i.e., slopes, among the groups were insignificant (). Still, by Wave 6, Medicinal Patients were estimated to use cannabis for sleep (mean = 3.31) or pain (mean = 3.14) between “half” and “most” of the time (, Supplemental Table S3). In contrast, both Recreational Patients and Recreational Users were estimated to use cannabis for sleep or pain between “some” and “half” of the time by Wave 6, i.e., in the range from 2 to 3. Differences in the intercepts or slopes of coping motives among the classes were insignificant.
Figure 2. Trajectories of health symptoms, cannabis use motives, and cannabis use across three longitudinal latent classes: Recreational Users (39.3%), Recreational Patients (40.4%), and Medicinal Patients (20.3%). The left Y-axis displays estimated mean scores (solid lines) and the right Y-axis displays estimated probabilities (dashed lines). Trajectories with statistically significant upward or downward slopes are represented by lines ending in arrows (see for slope p-values). Findings show that between waves 1–6, depression or/and anxiety symptoms increased in recreational groups and pain decreased in Recreational Patients (panels a, c, e). Pain motives, sleep motives, and concentrate use decreased in all groups, daily/near daily use decreased in Recreational Users and Medicinal Patients, and problematic cannabis use increased in Recreational Patients (panels b, d, f). BSI-GSI = Brief Symptom Inventory - Global Severity Index; BSI-ANX = BSI-Anxiety subscale; BSI-DEP = BSI-Depression subscale; BSI-SOMA = BSI-Somatization subscale; SDS = Severity of Dependence Scale; pain = current non-minor pain; W1-W6 = Waves of data collection.
Cannabis use
Patient groups had significantly higher initial levels of past 90-day daily/near daily cannabis use and concentrate use than Recreational Users (). By Wave 6, daily/near daily cannabis use decreased in Recreational Users and Medicinal Patients but remained stable in Recreational Patients, with significant differences in slopes between Recreational Patients and the other groups. Concentrate use decreased in all three groups. Problematic cannabis use did not significantly differ between the groups at baseline and was below the clinically significant level. Over time, however, Recreational Patients experienced an increase in problematic cannabis use score, approaching the clinical cutoff value of 4 by Wave 6.
Discussion
This is the first study to examine the longitudinal patterns of medicinal cannabis use among young adults during California’s transition from medical-only to adult-use legal cannabis to the best of our knowledge. Three unique patterns of longitudinal medicinal cannabis use emerged – Recreational Users, Recreational Patients, and Medicinal Patients – and each was associated with a specific profile of health symptoms, health-related motives, and cannabis use. While the probability of cannabis patient status was declining in each longitudinal class – a trend that started even pre-legalization – self-reported medicinal use appeared steady during this transitional period in all classes.
Recreational Users (39.3% of the sample) had low probabilities of both maintaining cannabis patient status and self-reporting medicinal cannabis use throughout the study. This class was characterized by a lower initial level of current pain, sleep, and pain motives, as well as daily/near daily use and concentrate use than the patient groups. Over time, the group experienced elevations in depression and anxiety symptoms, yet a decrease in current pain, sleep and pain motives, daily/near daily use, and concentrate use. While all were still using cannabis, this group may represent a typical subset of people who experiment with cannabis during adolescence or young adulthood but eventually transition out of cannabis use (Citation48,Citation49).
In contrast, Medicinal Patients, comprising one-fifth of the sample, included participants with an elevated initial probability of cannabis patient status and consistently high levels of self-reported medicinal cannabis use across the study period. Additionally, the group was marked by a higher proportion of older participants than Recreational Users, which is consistent with a study finding the highest prevalence of self-reported medicinal cannabis use among people aged 25–31 in North America (Citation18). Medicinal Patients had significantly higher baseline levels of sleep and pain motives, as well as non-minor pain and somatic symptoms compared to one or both recreational groups. Notably, by Wave 6 Medicinal Patients still used cannabis for sleep or pain at least half of all times cannabis was used – a finding that possibly explains the lack of significant reduction in current pain in this group. These results suggest a substantial degree of comorbidity of medical needs in this group and provide additional validation of the “genuine” status of some Medicinal Patients (Citation12). The group was also characterized by high baseline probability of daily/near daily cannabis use and concentrate use, though those levels decreased significantly over time.
Recreational Patients (40.4%) exhibited more wide-ranging characteristics. Participants in this group had a high-to-decreasing probability of patient status, yet a consistently low probability of self-reported medicinal use over time, even below that of Recreational Users. Such a discrepancy can potentially be linked to reports indicating that in medicinal-cannabis-only states, some cannabis patients obtain medical recommendation for legal access or protection from arrest (Citation12–15). Notably, the health symptoms or use motives of Recreational Patients resembled those of Recreational Users. Yet, the level of daily/near daily cannabis and concentrate use in this group was closer to that of Medicinal Patients. The decrease in the probability of 90-day concentrate use is an unexpected finding given heavy cannabis consumption in this group which warrants further investigation. Nevertheless, Recreational Patients was the only group with no reduction in daily/near daily cannabis use and increases in problematic use score approaching the clinical cutoff value. This finding aligns with research linking frequent cannabis use with developing cannabis dependence among young adults (Citation40,Citation47).
Whereas each class was characterized by specific trajectories of symptoms, motives, and severity of use, two trends emerged. First, there is a clear separation between the recreational groups and the medicinal group given the significantly higher baseline level of characteristics related to physical health among Medicinal Patients, i.e., somatic symptoms, current pain, and sleep and pain use motives (). Of note, group differences in mental health-related symptoms and motives were less pronounced with an increase in one or both mental health symptoms among recreational groups over time. Second, both patient groups were clearly distinct from Recreational Users by greater cannabis consumption (i.e., higher level of daily/near daily use and concentrate use) from baseline throughout the study. Certainly, by virtue of expanded access to legal cannabis, including its more potent forms, authorized patients often exhibit more intense patterns of cannabis use (Citation25,Citation31). Importantly, our results indicated that cannabis use with increased access but without clear medicinal purpose – as exhibited by Recreational Patients – was associated with increases in problematic cannabis use over time.
Our findings differ somewhat from previous longitudinal studies, which have reported improvements in pain (Citation22) or both pain and mental health (Citation23) in people who use cannabis for medicinal purposes. In contrast, our findings showed that Medicinal Patients – the group with clearer bonafide medicinal cannabis use – did not experience a change in pain or mental health symptoms over time; only Recreational Patients were marked by decline in current non-minor pain (which was low at baseline). Nonetheless, our study found no increases in deleterious physical or mental health symptoms among Medicinal Patients. At the same time, an essential clinical implication of this research is the importance of monitoring potential increases in mental health symptoms and cannabis-related problems among subsets of young adults who engage in recreational cannabis use.
Importantly, our results complement and build on previous studies examining medicinal cannabis use in the post-legalization period. Particularly, the present study extends our previous assessment, which reported reduction in the proportion of cannabis patients among young adults immediately following adult-use cannabis legalization in California (Citation10). This study demonstrated that the demand for participation in medical cannabis programs continued to decline at least for two years following the start of retail cannabis sales in all subgroups – a finding that is also corroborated by the downward trends in medical patient enrollment in several adult-use states (Citation9). Notably, to continue the legacy of medical cannabis programs, adult-use states often incentivize patient participation. For example, in California, registered patients are granted extended privacy and parental rights protections, allowed to purchase more cannabis than recreational users, and exempt from retail sales tax on medical cannabis (Citation50). Those incentives, however, can be offset by other factors as indicated by our earlier qualitative study with a subset of participants interviewed between 2020–2021 (Citation51) as well as other studies (Citation52–54). Particularly, the decision to let a medical cannabis recommendation expire can be affected by reduced legal concerns (Citation51,Citation52), inconvenience associated with medical recommendation renewal (Citation51,Citation53), as well as high prices of retail cannabis products in California despite patient discounts, which can prompt both medical and recreational users to pursue illicit markets (Citation51,Citation54). Additional research is needed to develop a more nuanced understanding of forces behind declining interest in medical cannabis program participation in adult-use states.
A compelling contribution of our study is that while adult-use legalization may reduce demand for participation in medical cannabis programs, it does not appear to impact self-reported medicinal use, which remained relatively stable (high or low) in each longitudinal group. Our results seemingly diverge from the longitudinal assessment of changes in self-reported medicinal use in Canada (Citation19), which could be explained by longer observation period in our study, our focus on young adults, as well as differences in how medicinal/recreational cannabis use was operationalized. Since our prior research has documented protective effects of self-reported medicinal cannabis use against the use of some illicit drugs (Citation55), we believe understanding how medicinal practices are learned and maintained is an important line of future research.
Though the impact of adult-use legalization on patterns of cannabis consumption was not a primary focus of this study, our findings suggest that the effects of adult-use legalization were minimal, which is consistent with several other studies focused on young adults (Citation6–8). The lack of increases in daily/near daily use and concentrate use post-legalization among the patient groups may be attributed to prior exposure to a wide range of cannabis products due to medical access. Yet, Recreation Users, the group that could be impacted by the adult-use legalization the most, did not increase consumption either despite new opportunities for access. This finding may illustrate the “ceiling effect” of age, as noted by Cerdá and colleagues (Citation6) as young adults’ cannabis use is already at the highest levels (Citation2). Moreover, the fact that participants aged six years over the course of the study to become 27 years-old on average by the end () and were likely transitioning to adult roles and responsibilities, could further counterweigh potential increases in cannabis use following legalization.
Several limitations of this study should be noted. All data are based upon self-report (except for medical cannabis patient status for Waves 1–3), which could be affected by recall bias. As such, the decline in patient status in Waves 4–6 could be due to self-reporting rather than effects of legalization. Additionally, the sample was not randomly selected and a third of the sample was lost to observation by the end of the study. However, during the recruitment, the cohort was monitored for the balance of key demographic characteristics, including age, race/ethnicity, and gender, and demographic differences between the attrition and retention subsamples by Wave 6 were insignificant. Finally, our study did not directly ask about perceived improvements in health or quality of life and those lines of inquiry should be pursued in future longitudinal studies.
In conclusion, this prospective observational study identified three distinct patterns of medicinal cannabis use among young adults during California’s transition to adult-use cannabis: Recreational Users, Recreational Patients, and Medicinal Patients. Initially, patient status (Recreational Patients and Medicinal Patients) was associated with greater cannabis consumption, while self-reported medicinal use (Medicinal Patients) was associated with a higher level of medical needs. Over time, recreational groups were characterized by increase in mental health symptoms and Recreational Patients in particular reported greater problematic cannabis use. Overall, while demand for medical cannabis patient access decreased, self-reported medicinal cannabis use remained stable among young adults during transition to adult-use cannabis.
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Download MS Word (34.6 KB)Acknowledgments
The authors would like to acknowledge the National Institute on Drug Abuse for funding the Cannabis, Health, and Young Adults (CHAYA) study, CHAYA’s Community Advisory Board for overseeing the research, and the following individuals who supported the development of this manuscript: Meagan Suen, Alisha Osornio, and Susie Choi.
Disclosure statement
Drs. Ataiants, Fedorova, and Lankenau receive research funding from Agronomed Biologics for a separate set of medical cannabis studies. Drs. Wong, Odejimi, and Conn declare no conflicts of interest.
Supplementary data
Supplemental data for this article can be accessed online at https://doi.org/10.1080/00952990.2024.2308098
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References
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