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. Author manuscript; available in PMC: 2022 Nov 1.
Published in final edited form as: Int J Drug Policy. 2021 May 30;97:103278. doi: 10.1016/j.drugpo.2021.103278

Associations Between Self-Reported Cannabis Use Frequency, Potency, and Cannabis/Health Metrics

Christine M Steeger 1, Leah N Hitchcock 2, Angela D Bryan 2,3, Kent E Hutchison 2,3, Karl G Hill 1, L Cinnamon Bidwell 2,3
PMCID: PMC8585676  NIHMSID: NIHMS1709855  PMID: 34062287

Abstract

Background.

Research shows that cannabis use frequency is associated with cannabis dependence and health metrics. However, much less is known about how self-reported cannabis potency (THC and CBD) may be associated with the same metrics, and whether any associations exist after accounting for frequency of cannabis use. Moreover, even less is known about how these relations may differ across cannabis product forms. This exploratory study examined 1) associations between cannabis frequency, potency, and cannabis/health metrics, and 2) whether associations between potency and cannabis/health metrics remained after controlling for frequency.

Methods.

Using a sample of adult recreational cannabis users in Colorado (N=300), we tested the relationship between self-reported cannabis use metrics of frequency and potency of flower, edible, and concentrate products with separate measures of problematic cannabis use (i.e., dependence, withdrawal, craving), depression, anxiety, and general perceived health.

Results.

Greater frequency of flower and concentrate (but not edible) use were associated with greater problematic cannabis use, and greater concentrate use frequency was also associated with more mental health problems. Partial correlations controlling for average frequency of use across all product forms and CBD potency per product showed that one significant association between THC potency and cannabis/health metrics remained (i.e., higher THC concentrate potency with better health), and one emerged (i.e., higher THC concentrate potency with lower cannabis withdrawal).

Conclusions.

Frequency of use is reliably associated with problematic cannabis use for flower and concentrates, but it did not account for all observed associations in this study. Differences in patterns of associations between frequency and potency and cannabis/health metrics across cannabis forms suggest a need for better understanding user reports of THC and CBD potency, individual differences among users, and improved measurement.

Keywords: Cannabis frequency of use, cannabis potency, THC, CBD, self-report, behavioral health

Introduction

The 2018 National Survey on Drug Use and Health (NSDUH) reported that 43.5 million people used cannabis in the past year, with increasing cannabis use trends among adults (SAMHSA, 2019). The increases in both cannabis use and wide variety of products available in retail markets underscore the critical need to understand the public health implications of the current cannabis landscape. Most existing cannabis research has examined the public health, mental health, and substance use and addiction consequences of how often cannabis is used, cannabis use frequency (e.g., monthly, weekly, daily) while ignoring cannabis potency. Greater frequency of use is a reliable predictor of cannabis use disorder symptoms, cannabis dependence, and other problematic outcomes (e.g., Buu, Hu, Pampati, Arterberry, & Lin, 2017; Casajuana et al., 2016; Curran et al., 2019). However, most of this work examined associations between frequency of cannabis flower/bud, leaving questions about relations between cannabis use frequency and outcomes across other product forms such as edibles and concentrates. For example, several reviews indicate that frequent and long-term cannabis use (of mostly flower/bud) may be associated with impaired cognition (Solowij & Battisti, 2008), problems in psychosocial, mental health, and physical health domains, and motor vehicle accidents (Hall & Degenhardt, 2014; Volkow et al., 2016). Further, other reviews call for updated research on how other dimensions of cannabis (e.g., potency) may be related to cannabis dependence and health outcomes (Freeman & Lorenzetti, 2019; Volkow, Baler, Compton, & Weiss, 2014).

The current cannabis legalization environment shows that cannabis potency (e.g., concentration of the psychoactive cannabinoid Δ9-tetrahydrocannabinol [THC]) has increased considerably over the past two decades (Chandra et al., 2019; ElSohly et al., 2016). Despite widespread increases in potency, little is known about how THC and other cannabinoids (e.g., cannabidiol; CBD) are related to problematic cannabis use (i.e., dependence, withdrawal, and craving), depression, anxiety, and general health. Further, even less is known about how potency may be related to these cannabis/behavioral health metrics across cannabis product forms including flower, edibles, and concentrates (e.g., hash oil, shatter, wax). A better understanding of the influence of cannabinoid potency, over and above simple frequency of use, is critical given the wide variability in the potency and forms of products on the legal cannabis market. This study therefore examined associations between cannabis frequency, THC and CBD potency, and cannabis/health metrics, and whether associations differed across product forms.

Relations between Potency and Cannabis/Health Metrics

Research indicates that higher THC cannabis potency may be associated with a range of negative outcomes, such as poorer cognitive functioning, increased risk of psychosis, and a greater potential for addiction than lower THC cannabis (Hall, 2015; Hall & Degenhardt, 2014). There is some evidence that high-potency cannabis may be more reinforcing than low-potency cannabis (Chait & Burke, 1994), which supports findings that high-potency cannabis may increase the likelihood of tolerance, dependence, and cannabis use disorder (Arterberry, Padovano, Foster, Zucker, & Hicks, 2019; Loflin & Earleywine, 2014; Meier, 2017; Ramesh & Haney, 2015). In addition to problematic patterns of use and dependence, studies have found that higher THC potency may contribute to problems in other domains such as other forms of substance use, poor mental health, and physical health consequences (Hall, Hoch, & Lorenzetti, 2019; Prince & Conner, 2019; Xue, Husain, Zhao, & Ravindran, 2020), unless users are able to titrate their cannabis doses (Freeman & Winstock, 2015; Hall, 2015).

Notably, most of the research on relations between cannabis potency and health outcomes is focused on levels of THC in cannabis flower. Less is known about behavioral and physical health effects of the other major cannabinoid, CBD, which is not intoxicating and may moderate the effects of THC (Freeman et al., 2019). Some studies report beneficial effects of CBD for decreasing risk of withdrawal symptoms and dependence associated with cannabis use disorder, mental health problems including anxiety and depression, physical pain/inflammation, and potential antipsychotic effects; however, other studies find weak or no associations between CBD and health outcomes (for reviews, see Blessing, Steenkamp, Manzanares, & Marmar, 2015; Freeman et al., 2019; Khan et al., 2020; Kosiba, Maisto, & Joseph, 2019). Little is known about how recreational cannabis users self-report THC and CBD potency across cannabis products, and how those are linked to cannabis use and health outcomes. The current study explored associations of self-reported THC and CBD across three of the most commonly used product forms on the legal market: flower, edibles, and concentrates.

Product Potency and Labelling in the Colorado Retail Market

A range of novel cannabis product forms are available in the retail market (Spindle, Bonn-Miller, & Vandrey, 2019). THC potency tends to be the focus of extraction, which can vary across product forms. For example, in Colorado dispensaries, 2017 statewide average estimates of product potencies were 19.6% THC for cannabis flower/bud and 68.6% THC for cannabis concentrates, with an upward limit of above 90% THC for high potency concentrates (e.g., hash and hash oil) (Orens, Light, Lewandowski, Rowberry, & Saloga, 2018). In the legal retail market, the State of Colorado requires that a universal THC symbol, along with potency profile information and testing statements are listed on cannabis product labels. Specifically, five cannabinoids are required to be tested for and reported by third party analytical laboratories in Colorado: (−)-D9-tetrahydrocannabinol (THC), cannabidiol (CBD), Tetrahydrocannabinolic acid A (THCA-A), cannabidiolic acid (CBDA), and cannabinol (CBN) (Code of Colorado Regulations, 2019). All of this labelling information is available to users/purchasers of state market products.

There is some recent evidence supporting the reliability of self-reported potency such that those who self-report on potency of legally-purchased products from Colorado dispensaries, report on it consistently across time (Martin-Willett et al., 2020). Other studies have explored cannabis users’ and non-users’ understanding of product labelling features, including potency and dosage information for edibles, and limitations of understanding product labelling in Colorado, Washington, and Canada (Hammond, 2019; Kosa, Giombi, Rains, & Cates, 2017; Leos-Toro, Fong, Meyer, & Hammond, 2020). For example, using focus groups of adult users and non-users of edibles, Kosa et al. (2017) reported that all participants found Colorado potency profile statements for edibles (i.e., potency in milligrams, number of THC servings, and whether cannabinoid potency was tested) important for consumers, though not all participants completely understood all labelling features. Despite limitations in full understanding of cannabis product label components, some recent evidence suggests that consumer knowledge of labelled THC and CBD potency may be higher in legal (versus non-legal) US states (e.g., Hammond & Goodman, 2020). Thus, it is possible that adult cannabis users may look for and read standardized product potency profiles and serving size statements (e.g., Kosa et al., 2017), and are better able to self-report product potencies in the context of an established Colorado legal market environment.

Potency across Cannabis Product Forms

Recent empirical work suggests that potency should be examined separately across cannabis product forms or route of administration to avoid obscuring effects between potency and health outcomes (Prince & Conner, 2019). The flower/bud product form has dominated retail market sales, accounting for two thirds of the market share (Orens et al., 2018) and has been the most widely studied form. Research on the health effects of cannabis shows generally positive associations between high THC flower/smoked cannabis potency and problematic cannabis use or mental health problems (Hall & Degenhardt, 2014; Hines et al., 2020; Russell, Rueda, Room, Tyndall, & Fischer, 2018). However, a recent study found that cannabis users who reported use of greater THC flower potency had fewer physical and mental health problems (Prince & Conner, 2019). Less work has focused on specific links between edible potency components and cannabis/health outcomes. It is clear that there are delayed effects with oral cannabis delivery methods (Nadulski et al., 2005), and some evidence suggests that overconsumption of edibles with high THC concentration can result in undesirable outcomes such as acute harms from intoxication or longer-term use consequences of psychosis and anxiety (Barrus et al., 2016; Matheson & Le Foll, 2020).

Growing evidence on concentrates and related cannabis/health effects shows that butane hash oil (or dabs, an extremely potent concentrate) may lead to higher self-reported tolerance and withdrawal (Loflin & Earleywine, 2014) or higher levels of physical dependence (Meier, 2017). Chan et al. (2017) found that butane hash oil as compared to high THC cannabis flower, was strongly associated with higher self-reported anxiety and depression and other illicit drug use. Concentrate users who reported using higher THC potency products also have more negative physical and mental health consequences (Prince & Conner, 2019). Other research shows that concentrate users endorsed more symptoms of cannabis use disorder and use higher strength cannabis even when using non-concentrated forms (Bidwell, YorkWilliams, Mueller, Bryan, & Hutchison, 2018). Additionally, Bidwell and colleagues found that frequent concentrate users did not differ significantly from frequent flower users on cannabis use disorder symptoms, suggesting needs for future work to examine whether frequency or forms of cannabis better explain associations with cannabis outcomes. Overall, current research highlights that not only should additional studies examine the effects of THC and CBD potency on cannabis use and health outcomes across product forms, but that it is also important to assess and account for frequency of use when comparing different cannabis product potency.

Purpose of Study

In this study, we seek to understand whether self-reported cannabinoid potency contributes to variance in cannabis/health metrics (i.e., cannabis dependence, withdrawal, and craving; depression; anxiety; and, general health) over and above frequency of use. We examined the following three exploratory research questions using a sample of adult recreational cannabis users.

  1. Is cannabis frequency of use related to cannabis/health metrics across flower, edible, and concentrate product forms?

  2. Is cannabis potency related to cannabis/health metrics across flower, edible, and concentrate product forms?

  3. Controlling for frequency of cannabis use, is cannabis potency associated with cannabis/health metrics across flower, edible, and concentrate product forms?

Methods

Study Sample and Procedures

Data were taken from a larger multi-study longitudinal project on cannabis, mood, and cognition for adult recreational cannabis users. Participants were recruited from 2017–2020 in the greater Denver-Boulder area of Colorado, United States, using social media postings and mailed flyers advertising to cannabis users. Informed consent was obtained from participants, and these studies were approved by the University of Colorado Boulder Institutional Review Board. A total of 300 participants who had data on pertinent study variables of self-reported cannabis use, potency, and health were included in the current analysis. The analyses reported herein were drawn from the baseline assessments of the larger study, with current research questions not overlapping with the larger project aims. Participants contacted trained research staff with their interest by phone or e-mail. Inclusion criteria were: 1) Aged between 21 and 70; 2) Used cannabis at least 4 times in the past month; 3) No other non-prescription drug use in the past 60 days; confirmed with a urine toxicology screen; 4) No daily tobacco use; 5) Drinking 2 times or fewer per week, and ≤ 3 drinks per occasion; 6) Not pregnant (verified via pregnancy test) or trying to become pregnant; and 7) Not receiving treatment for psychotic disorder or bipolar disorder.

Baseline Appointment

Participants were instructed not to use cannabis on the day of their study appointment. After informed written consent was obtained from participants, a breathalyzer and urinalysis test were administered to test for alcohol and other drug use, respectively. Participants completed questionnaires on demographics, lifestyle, substance use, health status and history, and completed detailed self-report measures of cannabis use. Other measures, such as biomarkers for cannabinoids and neurobehavioral tests, were also collected and are the focus of a prior report (Bidwell et al., 2020).

Measures

Self-reported demographic characteristics, cannabis frequency and potency, cannabis use metrics, and mental and physical health measures are described below. Internal consistency (measured by Cronbach’s alpha) is reported for aggregated measures.

Cannabis frequency.

Past month cannabis frequency of use was measured on a 0–11 scale. Frequency categories were 0 (I never use cannabis), 1 (Less than once a month), 2 (One day a month), 3 (Two days a month), 4 (Three days a month), 5 (One day a week), 6 (Two days a week), 7 (Three days a week), 8 (Four days a week), 9 (Five days a week), 10 (Six days a week), and 11 (Daily). Frequency of use response ranges were the same across three separate product forms: flower (“How often do you vaporize or smoke cannabis flower on average?”), edibles (“On average, how often do you consume cannabis orally or consume edibles? This question refers to anything that you consume orally like capsules, food, or drink [e.g., baked goods, candies, drinks, hemp oil, cannabis oil, Rick Simpson oil, tinctures, etc.]”), and concentrates (“On average, how often do you use cannabis concentrates [e.g., hash oil, shatter, wax]? For example, how many times do you take a dab?”). Additionally, we created a composite past month frequency of use variable by averaging frequency of flower, edibles, and concentrates use for all users, which included both single product and multiple product users. This variable was used as a control variable and represented a measure of overall (average) past month frequency of use across all product forms.

Cannabis potency.

Separate items of self-reported THC and CBD potency were also measured across the three product forms. Specific items were, “How much THC and/or CBD is in the cannabis flower that you use most often?”, “On average, how many milligrams (mg) of THC (or CBD) do you consume at one time when using cannabis orally?”, and “How much THC (or CBD) is in the concentrates that you use most often?” Participants reported percent potency of THC and CBD across categories 0–7. Potency category ranges were 0 (0%), 1 (less than 5%), 2 (5–10%), 3 (10–15%), 4 (15–20%), 5 (20–25%), 6 (25–30%), and 7 (greater than 30%) for flower and 0 (0%) 1 (less than 50%), 2 (50–60%), 3 (60–70%), 4 (70–80%), 5 (80–90%), 6 (90–100%), and 7 (100% isolate) for concentrates. THC and CBD potencies for edibles were reported as a scale in milligrams (mg), ranging from 0 mg to greater than 150 mg. In the legal Colorado retail market, dispensaries are required to report standardized cannabinoid potency information on product labels, including a total or range of THC and CBD values based on product testing variability (Code of Colorado Regulations, 2019). The percentages of flower and potency categories reflect how a large number of cannabis products are currently labelled in the legal Colorado market (e.g., a reported range of lab-tested potency components or an average % potency). Overlapping intervals provided cannabis users with general reference points for potency (strength) categories.

Cannabis metrics.

The Marijuana Dependence Scale (MDS; Stephens, Roffman, & Curtin, 2000) is a self-report cannabis use disorder measure based on DSM criteria, that includes items targeting dependence, withdrawal, and tolerance (e.g., “When I used marijuana, I often used more than I intended”). Individuals responded to each item with No or Yes (0/1). The MDS total score is a 9-item index, which was summed.

The Marijuana Withdrawal Checklist (MWC; Budney, Moore, Vandrey, & Hughes, 2003) 16-item total score was used to assess severity of withdrawal symptoms after the last time individuals used cannabis. Example items included symptoms such as shakiness/tremulousness, restlessness, sweating, sleep difficulty, headaches, and increased anger. Response options ranged from 0 (None) to 3 (Severe). The total score alpha was .89.

An adapted version of the Marijuana Craving Questionnaire (MCQ; Heishman, Singleton, & Liguori, 2001) measured degree of craving, from 0 (Not at all) to 10 (Strongest possible feeling). Items were adapted to include a wider response range in this study (0–10) compared to the original version (1–7). A 4-item average craving scale was created for this study. Specific items were, “I crave marijuana right now,” “I have a desire for marijuana right now,” “I have an urge to use marijuana right now,” and “All I want right now is to use marijuana.” The scale alpha was .89.

Mental health

Mental health was measured using the Beck Depression Inventory (BDI; Beck, Steer, & Brown, 1996) and Beck Anxiety Inventory (BAI; Beck, Epstein, Brown, & Steer, 1988). Respondents were asked how much they have been bothered by each current symptom during the past week, with responses ranging from 0 (Not at all) to 3 (Severely). This study used a 20-item subscale for the BDI (excluding a suicidal ideation item) and a 21-item BAI subscale. Alphas were .90 for depression and .91 for anxiety.

General health

General health was assessed with one item drawn from the Health Related Quality of Life (HRQL, SF-12; Ware Jr, Kosinski, & Keller, 1996) survey. The global health item asked individuals to rate their current health, “In general, how would you describe your overall health?” The item ranged from 1 (Poor) to 5 (Excellent), with higher scores indicating better health.

Analysis

The main analyses included the estimation of a series of partial correlations, which were conducted separately for each of the three product forms (flower, edibles, and concentrates). All analyses controlled for age and gender and examined separate associations between 1) cannabis use frequency and cannabis/health outcomes, 2) THC cannabis potency controlling for CBD potency and cannabis/health outcomes; and, 3) THC cannabis potency and cannabis/health outcomes controlling for average cannabis frequency of use across all product forms and CBD potency per product form. Partial correlations measure the strength and direction of a linear relationship between two continuous variables while controlling for the effect of one or more other variables (i.e., a covariate). Analyses comparing the significance and magnitude of correlations between cannabis potency and cannabis/health metrics while controlling for frequency of use will provide evidence for the role of frequency, accounting for any relationships between the variables in this study. For example, if a significant correlation exists between potency and a cannabis/health variable, but this correlation becomes nonsignificant, greatly reduced in magnitude, or changes direction after controlling for frequency of use, this provides evidence for a spurious relationship. However, if comparing the sets of correlations shows little change, this may suggest a direct relationship (i.e., frequency of use had little influence in controlling for the relationship between potency and the cannabis/health metric).

We used SPSS v.26 for all analyses. There were no missing response data for cannabis frequency of use, problematic cannabis use, mental health, and general health metrics. However, samples sizes per cannabis product form varied because of different numbers of users and non-users in the current study. Non-users of particular cannabis products were 3% (n=10) for flower, 14% (n=42) for edibles, and 40% (n=120) for concentrates. For flower, edible, and concentrate potency, missing response data were minimal (less than or about 5%), thus we used pairwise deletion for all exploratory analyses.

Results

Descriptive statistics for all demographic characteristics, cannabis frequency of use and potency, problematic cannabis use metrics, mental health, and general health are shown in Table 1. To summarize sample characteristics, adult participants were an average of 34.81 years (SD=14.9), over half male (58%), mostly White (78%), and generally well educated (51% had a bachelor’s degree or higher). As shown in Table 1, cannabis flower users indicated use between 4–5 days per week (i.e., 16–20 days per month; 51% were daily users), while edible and concentrate users indicated use between 2–3 days per month. Average reported potencies for cannabis flower were between 15–20% and 20–25% for THC and between less than 5% and 5–10% for CBD. Edible potency averaged 31.36 mg for THC and 12.74 mg for CBD. Concentrate potency averaged between 60–70% and 70–80% for THC and less than 50% for CBD.

Table 1.

Descriptive statistics of adult cannabis users

Variable N Mean or % SD Item, Scale, or Index Range
Demographics and characteristics
 Age 300 34.81 14.90 21–71
 Gender (Male %) 300 57.7% -- --
 Race (White %) 300 78% -- --
 Education (Bachelor’s degree or higher) 300 51.3% -- --
 Age at first regular use 294 21.4 9.74 13–66
Cannabis frequency & potency
 PM Flower frequency 300 8.70 = ~between 4–5 days/week 3.14 0–11 item
 PM Edible frequency 300 3.20 = ~between 2–3 days/month 3.16 0–11 item
 PM Concentrates frequency 300 3.03 = ~between 2–3 days/month 3.75 0–11 item
 PM All product forms average frequency 300 4.98 = ~about 1 day/week 2.10 0–11 item
 THC Flower potency 287 4.63 = ~15–25% 1.22 0–30% in 0–7 categ
 CBD Flower potency 284 1.81 = ~less than 5%−10% 1.50 0–30% in 0–7 categ
 THC Edible potency 251 31.36 40.76 0–150 mg
 CBD Edible potency 248 12.74 24.69 0–150 mg
 THC Concentrate potency 177 3.30 = ~60–80% 1.59 0–100% in 0–7 categ
 CBD Concentrate potency 169 .78 = ~0%-less than 50% 1.17 0–100% in 0–7 categ
Cannabis metrics
 MDS Total 300 1.96 2.18 0–9 index
 MWC Total 300 .46 .47 0–3 item
 MCQ Craving 300 1.71 2.02 0–10 item
Mental health
 BDI Depression 300 .31 .35 0–3 subscale
 BAI Anxiety 300 .29 .34 0–3 subscale
General health
 Good health 300 3.91 .83 1–5 item
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Note. PM = past month. Categ = categories. THC = Δ9-tetrahydrocannabinol. CBD = cannabidiol. MDS = Marijuana Dependence Scale. MWC = Marijuana Withdrawal Checklist. MCQ = Marijuana Craving Questionnaire. BDI = Beck Depression Inventory. BAI = Beck Anxiety Inventory.

Frequency of Cannabis Use and Cannabis/Health Metrics

First, to answer research question 1, correlation analyses tested associations between past month frequency of cannabis use across flower, edible, and concentrate product forms and cannabis/health metrics (see Table 2). Per individual product form, flower frequency of use was negatively correlated with edible frequency and positively correlated with concentrate frequency, and edible frequency was positively correlated with concentrate frequency. Average frequency of use across all three product forms was positively correlated with each frequency of use per individual product form (rs ranged from .47 for edibles to .81 for concentrates). Within flower users who also use concentrates, the patterns of associations were very similar for both concentrate frequency of use and average frequency of use across all products.

Table 2.

Correlations between cannabis past month frequency of use and cannabis/health metrics

Flower frequency Edible frequency Concentrate frequency All product forms average frequency
Variable N = 300 N = 300 N = 300 N = 300
Age −.08 .15** −.20** −.08
Gender (male) .00 −.07 .10 .03
Flower frequency -- −.21** .32** .58**
Edible frequency −.21** -- .14* .47**
Concentrate frequency .32** .14* -- .81**
All product forms average frequency .58** .47** .81** --
Problematic cannabis use
 MDS Dependence Total .16** −.07 .06 .08
 MWC Withdrawal Total .26** .02 .21** .26**
 MCQ Craving .23** .01 .22** .25**
Mental health problems
 BDI Depression .09 −.03 .15* .12*
 BAI Anxiety .10 .02 .18** .16**
General health
 Good health −.03 −.05 −.11 −.10
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Note. All correlations controlled for age and gender.

**

p < .01,

*

p < .05.

Higher flower frequency of use was positively associated with all three measures of problematic cannabis use, whereas higher concentrate frequency was positively correlated with two of three problematic cannabis use measures. Higher concentrate frequency of use was also associated with higher depression and anxiety symptoms. There were no significant associations between edible frequency of use and any problematic cannabis use outcome or health metric. Results for correlations between average frequency of use across all product forms and outcomes followed the same pattern of effects as for concentrate frequency of use—average frequency of use across all product forms was positively associated with cannabis withdrawal, craving, depression and anxiety (rs ranged from .12 for depression to .26 for withdrawal).

Potency of Cannabis and Cannabis/Health Metrics

To answer research question 2, we examined correlations between THC cannabis potency and cannabis/health metrics controlling for CBD potency per product form (see Table 3). First, for flower, there were no significant associations between THC potency and any outcome. For edibles, use of higher THC potency was associated with greater withdrawal and cannabis craving and poor general health. For concentrates, use of higher THC potency was positively correlated with only good general health.

Table 3.

Correlations between THC cannabis potency use and cannabis/health metrics controlling for CBD per product form

Potency of THC Flower Used Potency of THC Edibles Used Potency of THC Conc. Used
Variable N = 284–287 N = 248–251 N = 169–177
Age −.02 −.13* −.17*
Gender (male) −.08 .11 .28**
Problematic cannabis use
 MDS Dependence Total −.06 .06 .01
 MWC Withdrawal Total −.03 .19** −.12
 MCQ Craving .08 .15* .04
Mental health problems
 BDI Depression −.03 .03 −.07
 BAI Anxiety −.06 −.04 −.10
General health
 Good health .06 −.13* .20*
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Note. All correlations also controlled for age and gender. Conc. = concentrates.

**

p < .01,

*

p < .05.

Separate THC and CBD potency correlations with frequency of use and within each cannabis product form are presented in Table 4. Greater frequency of use per product form was positively associated with use of THC flower potency, CBD edible potency, and THC concentrate potency (rs ranged from .14 for flower to .32 for concentrates) and negatively associated with CBD flower potency (see Table 4). There were no significant associations between frequency of use and THC edible potency or CBD concentrate potency. Greater average frequency of use across all product forms was positively correlated with THC flower potency, THC and CBD edible potency, and THC concentrate potency (rs ranged from .14 for flower to .32 for edibles) and negatively correlated with CBD flower potency. Average frequency of use across all product forms was not correlated with CBD concentrate potency.

Table 4.

Correlations between frequency of use and potency of THC and CBD cannabis used

Potency of THC Flower Used Potency of CBD Flower Used Potency of THC Edibles Used Potency of CBD Edibles Used Potency of THC Conc. Used Potency of CBD Conc. Used
Variable N = 284–287 N = 248–251 N = 169–177
Age −.02 .11 −.13* .01 −.17* −.09
Gender (male) −.08 −.20** .11 .06 .28** −.09
Frequency of use per product form .14* −.15* −.04 .15* .32** .07
All product forms average frequency .14* −.12* .32** .17** .24** .05
Potency of THC flower used --
Potency of CBD flower used .06 --
Potency of THC edibles used .15* −.02 --
Potency of CBD edibles used .05 .27** .50** --
Potency of THC concentrates used .35** −.11 .11 .03 --
Potency of CBD concentrates used −.01 .41** −.04 .06 .21** --
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Note. All correlations controlled for age and gender. Conc. = concentrates.

**

p < .01,

*

p < .05.

Within each cannabis product form, results of THC and CBD potency correlations showed that THC and CBD potencies were positively correlated for edibles and concentrates (but not flower; see Table 4). Across products, THC flower potency was positively correlated with THC edible potency and THC concentrate potency (rs = .15 and .35), but THC edible potency and THC concentrate potency were uncorrelated. Similarly, CBD flower potency was positively correlated with both CBD edible and concentrate potencies (rs = .27 and .41), but CBD edible potency and CBD concentrate potency were uncorrelated. These results suggest that those who reported higher use of THC or CBD potency in one product form also generally reported higher use of THC or CBD potency in another form. However, results may be at least partially due to use of high THC and high CBD potency in the same edible or use of high THC in one and high CBD potency in another edible, which we are unable to parse in this study. Thus, we controlled for CBD potency in main analyses.

Cannabis Potency and Cannabis/Health Metrics Controlling for Frequency of Use

Finally, to answer research question 3, we examined correlations between cannabis potency and cannabis/health metrics while controlling for average cannabis frequency of use across all product forms and CBD potency per product form (see Table 5). Comparing results in Table 5 with Table 3 (not controlling for average frequency of use across all product forms) showed that THC flower potency was still not significantly associated with any health outcomes. Use of higher THC edible potency was no longer significantly associated with withdrawal, craving, or general health, suggesting that average frequency of use across all product forms contributed variance to these cannabis and health outcomes. However, use of higher THC concentrate potency remained associated with better general health. Additionally, one significant negative correlation emerged for THC concentrate potency after controlling for average frequency of use across all product forms, such that higher THC concentrate use was associated with lower withdrawal.

Table 5.

Correlations between THC cannabis potency used and cannabis/health metrics controlling for average frequency of use across all product forms and per product CBD

Potency of THC Flower Used Potency of THC Edibles Used Potency of THC Conc. Used
Variable N = 284–287 N = 248–251 N = 169–177
Age −.02 −.13* −.17*
Gender (male) −.08 .11 .28**
Problematic cannabis use
 MDS Dependence Total −.08 .04 −.01
 MWC Withdrawal Total −.07 .12 −.19*
 MCQ Craving .05 .09 −.02
Mental health problems
 BDI Depression −.04 −.00 −.10
 BAI Anxiety −.09 −.09 −.14
General health
 Good health .08 −.10 .23**
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Note. All correlations also controlled for age and gender. Conc. = concentrates.

**

p < .01,

*

p < .05.

Discussion

This exploratory study examined patterns of associations between self-reported cannabis frequency of use, THC and CBD potency, and cannabis/health metrics, and tested whether associations between potency and cannabis/health metrics remained after controlling for average frequency of use across all product forms. Overall, results showed different patterns of correlations across cannabis product forms for all analyses, which is consistent with recent research highlighting that cannabis product forms and/or mode of use should be investigated separately (Gunn, Aston, Sokolovsky, White, & Jackson, 2020; Prince & Conner, 2019). Also consistent with other work is the finding that past month frequency of flower use and concentrate use were associated with greater problematic cannabis use metrics (Curran et al., 2019; Gunn et al., 2020; Swan, Ferro, & Thompson, 2020), and higher concentrate use frequency was associated with greater anxiety (Chan et al., 2017; Hines et al., 2020). However, we did not find that edible use frequency was associated with any cannabis or other health metric. It is possible that this result may be sample specific (i.e., mostly flower users and occasional concentrate and edible users) and should be replicated in other studies.

Next, results of frequency of use and potency correlations showed varying associations across product forms. The finding that greater frequency of use was correlated with greater THC flower potency and greater THC concentrate potency may be an indicator for higher tolerance of cannabis. For example, as users may develop a tolerance for high THC concentrate potency, they may need to use more and stronger cannabis products to achieve their desired high (Loflin & Earleywine, 2014; Russell et al., 2018).

We found that both THC and CBD potency were moderately correlated across all three product forms, with the exception of no correlation between CBD edible and concentrate potencies. That is, those who used higher THC (or CBD) potency in one product form (e.g., flower) also used higher THC (or CBD) potency in another form (e.g., concentrates). We also found that within product form, THC and CBD were positively correlated for edibles and concentrates (but not flower). While it is somewhat expected that there would be a positive correlation between THC and CBD content, particularly in highly potent products, we were unable to determine within and across product combined THC and CBD concentrations (e.g., potency ratios) as this study was limited to simple self-reported separate potency components. Future work will benefit from examining THC/CBD ratios (see below for further discussion) and how ratios may be similar or different across patterns of product forms of use. Further, some research shows that basic labelling standards of retail edible and other products may not be accurate (i.e., exact THC and CBD potency % on product labels) and need to be improved (Bonn-Miller et al., 2017; Vandrey et al., 2015). For example, the State of Colorado allows for a plus or minus 15% potency variance on retail cannabis products (Code of Colorado Regulations, 2019), due to differences in potency lab testing. These current regulations in Colorado and other legalized states suggest necessary improvements in testing accuracy standards and refinement of state potency reporting laws on product labels. In addition to improving testing and product labelling standards, a growing area of research interest in educating consumers on both labelling potency and dosage of cannabis products may further help with understanding separate and combined THC and CBD components (Hammond, 2019; Hammond & Goodman, 2020; Hindocha, Norberg, & Tomko, 2018; Leos-Toro et al., 2020).

Main Analyses of Potency and Cannabis/Health Metrics Controlling for Frequency of Use

Our primary findings showed that only one significant association between THC potency and problematic cannabis use or health outcomes remained significant, after controlling for average frequency of use across all product forms and CBD potency per product form—higher THC concentrate potency remained significantly associated with better general health. This is an interesting finding because we controlled for age and gender in all analyses, which rules out the potential explanation that younger compared to older age accounted for these results. Thus, this association may at least partially be a function of this study’s generally healthy/high-functioning sample of adults with an average age of mid-30s. Other results showed that for edibles, THC potency was no longer significantly associated with cannabis withdrawal, cannabis craving, or general health after controlling for frequency of use. These results suggest that average frequency of use across all product forms primarily accounted for the variance in problematic cannabis use and health outcomes for edibles.

Controlling for average frequency of use across all product forms showed an interesting pattern for THC concentrate potency – one negative association emerged between THC concentrate potency and cannabis withdrawal. In prior analyses, concentrate frequency of use was positively associated with withdrawal. The most likely explanation is that this association is the result of statistical suppression and is an artifact. That is, controlling for frequency of use when potency is not associated with some of the cannabis/health variables may lead to spurious findings. We note that there were different coefficient signs (i.e., one positive and one negative direction) for the frequency of use and THC concentrate potency correlation with cannabis withdrawal. Therefore, frequency of use may be conflated with THC and CBD potency and cannabis/health metrics in some analyses.

A possible substantive explanation that should be explored in future work is whether these observed associations for concentrates and cannabis/health metrics may be different in high functioning users (i.e., those with relatively low levels of problematic substance use behavior and with good health), like in this study. Results may suggest that individuals who had higher withdrawal used concentrates more often, but when they used concentrates, they used less potent THC. Our findings are contrary to other studies reporting positive associations between high-potency cannabis concentrate use and physical dependence or physical health problems (Chan et al., 2017; Meier, 2017). It is possible that results may be different for predominately concentrate users versus users with preferences for other product forms. In the current study, most participants can be characterized as mainly flower users and occasional concentrate (or edible) users. Additional research in this area should examine whether users predominantly use one cannabis form versus multiple product forms, as well as user characteristics including level of functioning/health and substance use problems.

Limitations and Future Directions

This study has several limitations. First, all measures were only self-reported among adult cannabis users. Biological measures are necessary to accurately measure cannabis potency components and true cannabinoid exposure (Curran et al., 2019), and should be used in addition to self-report cannabis measures. Limited research has measured the validity of self-reported potency measures. One study examining self-reported cannabis potency and dose among frequent young adult Dutch users found that associations between subjective potency estimates (i.e., very mild to very strong) and THC concentration were weakly associated, but that subjective measures have at least some validity (van der Pol et al., 2013). In another study conducted in the United Kingdom, Freeman et al. (2014) found a modest positive association between estimated potency strength (i.e., self-rated from negligible effect to incredibly strong) and THC content for different cannabis types, which indicated some validity of relations between potency ratings and cannabinoids. Further research is needed in this area, including incorporating actual cannabis product testing of THC and CBD potency or product labelling information into studies using self-report methods.

Second, we did not assess the source of self-reported potency, so we could not determine whether users reported potency information from labels of legally-purchased products or products used from the illegal cannabis market. Future work in this area should measure where users obtained their products to further help understand user knowledge of potency labelling information. Third, the extent to which products contained both THC and CBD was not measured in this study. Products containing different ratios of THC to CBD reflect current use trends and diversity of available products in legalized retail markets (Chandra et al., 2019). As most cannabis research is based on flower/smoked products, it will be important to continue to explore associations across various product forms and with CBD and other cannabis components, ideally in controlled trials (Barrus et al., 2016).

Fourth, this study did not measure quantity of cannabis use. Recent work shows the importance of measuring cannabis potency and quantity together (e.g., % cannabinoid content, product weight, and amount of product used) to inform recommendations for product dosage and safer consumption practices (e.g., Freeman & Lorenzetti, 2019; Hammond, 2019; Parnes, Bravo, Conner, & Pearson, 2018). Fifth, our average frequency measure represents frequency of use across all forms for both those who have used or not used a product. Future work should examine additional ways to measure overall frequency of use when including several cannabis products in the same study (e.g., summing use across product forms, average use across product forms for single-product users and multiple-product users).

Sixth, the cross-sectional nature of the data precludes interpreting any causal effects among cannabis frequency, potency, and outcomes. Correlation coefficient sizes were generally small to medium in magnitude and should not be over-interpreted, suggesting other variables contribute to the variance in effects. This study used a high-functioning and overall healthy sample, and restriction of range may have been a factor for some analyses. Future research should examine these associations longitudinally with problematic cannabis use, mental health problems, and physical health as outcomes.

Seventh, our sample was recruited from a single US state; our findings should be replicated in other states and countries. Lastly, we used a sample of adults who were recruited as recreational cannabis users. There is likely heterogeneity in types of users in the present study’s sample, including patterns of use and reasons for use which could have included medical use. Sznitman (2017) found sample differences across recreational, unlicensed and licensed medical users in method of use and patterns of use. Future research should explore associations between CBD, THC/CBD ratios, other cannabinoid potency and cannabis/health outcomes for recreational compared to medically motivated cannabis users (Lin, Ilgen, Jannausch, & Bohnert, 2016). Additionally, many cannabis users use multiple cannabis products, have varying methods of use, or are polyusers of cannabis, tobacco and alcohol (Gunn et al., 2020; Swan et al., 2020). Future studies will benefit from addressing complexities in user characteristics and patterns of use for infrequent to regular user types, including craving for specific products, which may affect problematic cannabis use and other health outcomes (e.g., Gunn et al., 2020).

In summary, this study adds to the literature on associations between self-reported cannabis frequency of use, separate potency measures of THC and CBD, and cannabis/health metrics among adult recreational cannabis users. We explored associations among three types of cannabis forms (flower, edibles, concentrates) and found different patterns of effects both across product forms and between frequency and potency and cannabis/health metrics. Frequency of use was reliably associated with problematic cannabis use for flower and concentrates (but not edibles), though it did not account for all observed associations in this study. Frequency may be an important confounding variable in cannabis measurement when examining the contributions of potency to cannabis use and health problems. This study highlights that although frequency of use remains important, cannabis potency is also an important and understudied aspect of cannabis research. Studying both of these dimensions together will help us better understand the public health consequences of cannabis use.

Highlights.

  • Higher frequency of flower and concentrate use was related to cannabis use problems

  • Frequency of concentrate use was positively correlated with anxiety and depression

  • Cannabis frequency of use was more reliably associated with outcomes than potency

  • Associations between potency and cannabis/health metrics varied across product form

  • Research should account for frequency of use when examining cannabis potency

Acknowledgements:

This research was funded by the National Institutes of Health (grant number DA039707 to KEH), and development of this paper was supported, in part, by the Institute of Behavioral Science Research Development Award.

Footnotes

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Declaration of interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Ethics approvals

The authors (Steeger, Hitchcock, Bryan, Hutchison, Hill, & Bidwell) certify that the manuscript contains a statement that informed consent was obtained for all participants and all procedures were performed in compliance with and approved by the University of Colorado Institutional Review Board.

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