The 'grass ceiling': limitations in the literature hinder our understanding of cannabis use and its consequences

Typical Hits, Grams, or Joints: Evaluating Cannabis Survey Measurement Strategies for Quantifying Consumption

Aim: Standardized survey measures that capture diverse cannabis consumption patterns are needed to inform public health and policy. Our team is developing a flexible, personalized, low-burden survey item inventory to measure cannabis use patterns and estimate milligrams of THC (mgTHC) consumption in large samples. This study aimed to identify measurement gaps and analysis implications associated with an initial pool of candidate items that assessed use of cannabis flower and concentrate products (smoked and/or vaporized). Methods: Adult cannabis consumers (n=4247) completed an online survey assessing cannabis use frequency, quantity, product types, product potencies (%THC), and methods of administration. Participants chose to report their consumption quantities using one of three units: "hits per day," "grams per week," or "joints per week." Respondents also indicated whether their past 7-day consumption pattern represented their typical pattern. Results: Eighty-one percent had used cannabis daily in the past week. Thirty-two percent, 53%, and 15% chose to report flower and concentrate consumption quantity in hits, grams, and joints, respectively. Approximately 80-90% of responses for the number of hits, grams, and joints consumed were less than the maximum response option-suggesting that response options captured the full range of potential cannabis consumption behaviors. Those who chose grams or joints units were generally more likely to endorse higher risk cannabis use (e.g., morning use, high %THC products) in the past week than those who chose the hits unit (adjusted Odds Ratio range: 1.2-3.9). Among those who reported that the past week represented their typical behavior (83%), past 30-day and past 7-day frequencies were highly correlated (Spearman's Rho=0.77)-supporting the feasibility of using lower burden "typical week" items to extrapolate patterns beyond a 1-week time frame. Conclusion: Results from this online convenience sample of frequent cannabis consumers suggest that the current items yield coherent and expected response patterns. Although additional testing is required, a standardized, flexible survey instrument for large-scale assessment of cannabis patterns and calculation of mgTHC seems within reach.

Exploring survey methods for measuring consumption quantities of cannabis flower and concentrate products

Background: Researchers need accurate measurements of cannabis consumption quantities to assess risks and benefits. Survey methods for measuring cannabis flower and concentrate quantities remain underdeveloped.Objective: We examined "grams" and "hits" units for measuring flower and concentrate quantities, and calculating milligrams of THC (mgTHC).Methods: Online survey participants (n = 2,381) reported preferred unit (hits or grams), past-week hits and grams for each product, and product %THC. Quantile regression compared mgTHC between unit-preference subgroups. Hits-based mgTHC calculations assumed a universal grams-per-hit ratio (GPHR). To examine individualized GPHRs, we tested a "two-item approach," which divided total grams by total hits, and "one-item approach," which divided 0.5 grams by responses to the question: "How many total hits would it take you to finish 1/2 g of your [product] by [administration method]?"Results: Participants were primarily daily consumers (77%), 50% female sex, mean age 39.0 (SD 16.4), 85% White, 49% employed full-time. Compared to those who preferred the hits unit, those who preferred the grams unit reported consuming more hits and grams, higher %THC products, and consequently, larger median mgTHC (flower-hits mgTHC: 32 vs. 91 (95%CI: 52-67); flower-grams mgTHC: 27 vs. 113 (95%CI: 73-95); concentrate-hits mgTHC: 29 vs. 59 (95%CI: 15-43); concentrate-grams mgTHC: 61 vs. 129 (95%CI: 43-94)). "Two-item" and "one-item" approach GPHRs were similar and frequently 50% larger or smaller than the universal GPHR.Conclusion: Allowing respondents to choose "hits" or "grams" when reporting cannabis quantities does not compromise mgTHC estimates. A low-burden, one-item approach yields individualized "hit sizes" that may improve mgTHC estimates.

Income inequality and daily use of cannabis, cigarettes, and e-cigarettes among Canadian secondary school students: Results from COMPASS 2018-19

INTRODUCTION

Cannabis, cigarette, and e-cigarette use among Canadian adolescents is a major public health concern. Income inequality has been associated with adverse mental health among youth and may contribute to the risk of frequent cannabis, cigarette, and e-cigarette use. We tested the association between income inequality and the risk of daily cannabis, cigarette, and e-cigarette use among Canadian secondary school students.

METHODS

We used individual-level survey data from Year 6 (2018/19) of Cannabis, Obesity, Mental health, Physical activity, Alcohol use, Smoking, and Sedentary Behavior (COMPASS) and area-level data from the 2016 Canadian Census. Three-level logistic models were used to assess the relationship between income inequality and adolescent daily and current cannabis use, cigarette smoking, and e-cigarette use.

RESULTS

The analytic sample included 74,501 students aged 12-19. Students were most likely to report being male (50.4%), white (69.1%), and having weekly spending money over $100 (23.5%). We found that a standard deviation unit increase in Gini coefficient was significantly associated with increased likelihood of daily cannabis use (OR=1.25, 95% CI = 1.01-1.54) when adjusting for relevant covariates. We found no significant relationship between income inequality and daily smoking. While Gini was not significantly associated with daily e-cigarette use, we observed a significant interaction between Gini and gender (OR=0.87, 95% CI= 0.80-0.94), indicating that increased income inequality was associated with higher risk of reporting daily e-cigarette use among females only.

DISCUSSION

An association between income inequality and the likelihood of reporting daily cannabis use across all students and daily e-cigarette use in females were observed. Schools in higher income inequality areas may benefit from targeted prevention and harm reduction programs. Results emphasize the need for upstream discussion on policies that can mitigate the potential effects income inequality.

A Review of Historical Context and Current Research on Cannabis Use in India

Background

The cultivation and use of cannabis is historically rooted in the Indian subcontinent and this rich heritage of cannabis use dates back to at least two thousand years. Cannabis remains an illicit substance in India despite its changing status globally with many countries legalizing cannabis use in recent years. Scientific research on cannabis use in India has also been sparse.

Method

Extensive search of online databases resulted in the identification of 29 original research studies pertaining to one of three areas of cannabis research; a) prevalence of cannabis use b) psychological correlates of cannabis use, c) cannabis use in substance use treatment settings.

Findings

We found that most Indian studies used very basic quantitative research designs and had poor scientific rigor. Samples were small, region specific and included only males. Data analyses were limited to descriptive methods. The criteria for cannabis use in most of the reviewed studies were not rigorous and prone to biases.

Conclusion & Implications

With changing attitudes and loosening of restrictions on cannabis use, the prevalence of new users is rising dramatically particularly in the college going population. This presents a strong need for research on motivations and attitudes to cannabis use and how those can influence patterns of use, and also the short- and long-term effects of use. More studies with stronger research designs (both cross sectional and longitudinal) are required for the study of cannabis use and this knowledge will be critical for managing the growing substance epidemic, generating public health solutions as well as formulating effective policy frameworks.

The International Cannabis Toolkit (iCannToolkit): a multidisciplinary expert consensus on minimum standards for measuring cannabis use

BACKGROUND

The lack of an agreed international minimum approach to measuring cannabis use hinders the integration of multidisciplinary evidence on the psychosocial, neurocognitive, clinical and public health consequences of cannabis use.

METHODS

A group of 25 international expert cannabis researchers convened to discuss a multidisciplinary framework for minimum standards to measure cannabis use globally in diverse settings.

RESULTS

The expert-based consensus agreed upon a three-layered hierarchical framework. Each layer-universal measures, detailed self-report and biological measures-reflected different research priorities and minimum standards, costs and ease of implementation. Additional work is needed to develop valid and precise assessments.

CONCLUSIONS

Consistent use of the proposed framework across research, public health, clinical practice and medical settings would facilitate harmonisation of international evidence on cannabis consumption, related harms and approaches to their mitigation.

Clinical Approaches to Cannabis: A Narrative Review

Cannabis use in the United States is growing at an unprecedented pace. Most states in the United States have legalized medical cannabis use, and many have legalized nonmedical cannabis use. In this setting, health care professionals will increasingly see more patients who have questions about cannabis use, its utility for medical conditions, and the risks of its use. This narrative review provides an overview of the background, pharmacology, therapeutic use, and potential complications of cannabis.

Cannabis based medicines and cannabis dependence: A critical review of issues and evidence

Cannabis has been legalised for medical use in an ever-increasing number of countries. A growing body of scientific evidence supports the use of medical cannabis for a range of therapeutic indications. In parallel with these developments, concerns have been expressed by many prescribers that increased use will lead to patients developing cannabis use disorder. Cannabis use disorder has been widely studied in recreational users, and these findings have often been projected onto patients using medical cannabis. However, studies exploring medical cannabis dependence are scarce and the appropriate methodology to measure this construct is uncertain. This article provides a narrative review of the current research to discern if, how and to what extent, concerns about problems of dependence in recreational cannabis users apply to prescribed medical users. We focus on the main issues related to medical cannabis and dependence, including the importance of dose, potency, cannabinoid content, pharmacokinetics and route of administration, frequency of use, as well as set and setting. Medical and recreational cannabis use differs in significant ways, highlighting the challenges of extrapolating findings from the recreational cannabis literature. There are many questions about the potential for medical cannabis use to lead to dependence. It is therefore imperative to address these questions in order to be able to minimise harms of medical cannabis use. We draw out seven recommendations for increasing the safety of medical cannabis prescribing. We hope that the present review contributes to answering some of the key questions surrounding medical cannabis dependence.

Characterising heterogeneity in the use of different cannabis products: latent class analysis with 55 000 people who use cannabis and associations with severity of cannabis dependence

BACKGROUND

As new cannabis products and administration methods proliferate, patterns of use are becoming increasingly heterogeneous. However, few studies have explored different profiles of cannabis use and their association with problematic use.

METHODS

Latent class analysis (LCA) was used to identify subgroups of past-year cannabis users endorsing distinct patterns of use from a large international sample (n = 55 240). Past-12-months use of six different cannabis types (sinsemilla, herbal, hashish, concentrates, kief, edibles) were used as latent class indicators. Participants also reported the frequency and amount of cannabis used, whether they had ever received a mental health disorder diagnosis and their cannabis dependence severity via the Severity of Dependence Scale (SDS).

RESULTS

LCA identified seven distinct classes of cannabis use, characterised by high probabilities of using: sinsemilla & herbal (30.3% of the sample); sinsemilla, herbal & hashish (20.4%); herbal (18.4%); hashish & herbal (18.8%); all types (5.7%); edibles & herbal (4.6%) and concentrates & sinsemilla (1.7%). Relative to the herbal class, classes characterised by sinsemilla and/or hashish use had increased dependence severity. By contrast, the classes characterised by concentrates use did not show strong associations with cannabis dependence but reported greater rates of ever receiving a mental health disorder diagnosis.

CONCLUSIONS

The identification of these distinct classes underscores heterogeneity among cannabis use behaviours and provides novel insight into their different associations with addiction and mental health.

Depression level, not pain severity, is associated with smoked medical marijuana dosage among chronic pain patients

BACKGROUND

The use of medical marijuana (MM) for the treatment of chronic pain is rapidly growing in the United States and Europe; however there is concern regarding the specificity of its therapeutic effects and the motivation underlying its use. While research indicates that among chronic pain prescribed opioids, depression has been associated with increased opioid dosage (regardless of pain levels), the extent to which depression and pain each contribute to MM dose among chronic pain patients is yet unknown.

METHODS

This cross-sectional study included 209 chronic pain patients prescribed smoked MM, in flower or other plant form, with no concurrent opioid treatment. Ordinal regression analyses were performed in order to explore the unique contribution of mean pain level (1-10 scale), depression severity (measured by the Patient Health Questionnaire (PHQ-9)) and anxiety severity (measured by the Generalized Anxiety Disorder scale (GAD-7)) to doses of MM, while taking into account additional sociodemographic and clinical factors.

RESULTS

Individuals with mild depression and those with moderate to severe depression were at significantly increased odds for using higher doses of MM in grams per month(Adjusted Odds Ratio(AOR) = 2.06,95% Confidence Interval(CI) = 1.05-4.01, and AOR = 5.95,95% CI = 1.97-17.98, respectively) compared to those without depression. In addition, individuals with mild depression were at significantly increased odds for smoking more MM joints daily(AOR = 2.07, 95% CI = 1.01-4.23) compared to individuals without depression. Mean levels of pain or anxiety severity were not significantly associated with either dose measures.

CONCLUSIONS

Depression and MM dose are highly correlated and should be concurrently addressed during chronic pain treatment.

'Standard THC units': a proposal to standardize dose across all cannabis products and methods of administration

BACKGROUND AND AIMS

Cannabis products are becoming increasingly diverse, and vary considerably in concentrations of ∆⁹ -tetrahydrocannabinol (THC) and cannabidiol (CBD). Higher doses of THC can increase the risk of harm from cannabis, while CBD may partially offset some of these effects. Lower Risk Cannabis Use Guidelines currently lack recommendations based on quantity of use, and could be improved by implementing standard units. However, there is currently no consensus on how units should be measured or standardized among different cannabis products or methods of administration.

ARGUMENT

Existing proposals for standard cannabis units have been based on specific methods of administration (e.g. joints) and these may not capture other methods, including pipes, bongs, blunts, dabbing, vaporizers, vape pens, edibles and liquids. Other proposals (e.g. grams of cannabis) cannot account for heterogeneity in THC concentrations among different cannabis products. Similar to alcohol units, we argue that standard cannabis units should reflect the quantity of primary active pharmacological constituents (dose of THC). On the basis of experimental and ecological data, public health considerations and existing policy, we propose that a 'standard THC unit' should be fixed at 5 mg THC for all cannabis products and methods of administration. If supported by sufficient evidence in future, consumption of standard CBD units might offer an additional strategy for harm reduction.

CONCLUSIONS

Standard ∆⁹ -tetrahydrocannabinol (THC) units can potentially be applied among all cannabis products and methods of administration to guide consumers and promote safer patterns of use.

Association Between the Use of Cannabis and Physical Violence in Youths: A Meta-Analytical Investigation

OBJECTIVE

The aim of this meta-analysis was to investigate the extent to which cannabis use among youths is associated with the risk of perpetrating physical violence.

METHODS

Searches were conducted in PubMed, PsycINFO, Web of Science, and Google Scholar for articles published from the inception of each database to July 2019. All studies that examined both cannabis use and the perpetration of physical violence in a sample of youths and young adults <30 years old were included. The meta-analysis was performed with a random-effects model. Risk of publication bias was assessed with Egger's test. Guidelines from the Meta-Analysis of Observational Studies in Epidemiology were followed.

RESULTS

After screening 11,348 potential studies, 30 study arms were included, yielding a total of 296,815 adolescents and young adults. The odds ratio for the pooled studies was 2.11 (95% CI=1.64, 2.72). The pooled odds ratios were 2.15 (95% CI=1.58, 2.94) and 2.02 (95% CI=1.26, 3.23) for the cross-sectional and longitudinal studies, respectively. Preliminary evidence suggests that the risk of violence was higher for persistent heavy users (odds ratio=2.81, 95% CI=1.68, 4.74) compared with past-year users (odds ratio=2.05, 95% CI=1.5, 2.8) and lifetime users (odds ratio=1.94, 95% CI=1.29, 2.93). The odds ratio for unadjusted studies was 2.62 (95% CI=1.89, 3.62), and for studies using odds ratios adjusted for potential confounding factors, 2.01 (95% CI=1.57, 2.56).

CONCLUSIONS

These results demonstrate a moderate association between cannabis use and physical violence, which remained significant regardless of study design and adjustment for confounding factors (i.e., socioeconomic factors, other substance use). Cannabis use in this population is a risk factor for violence.

Systematic Review of Cannabis Use and Risk of Occupational Injury

Aim: A range of nations, including countries of the European Union, Australia, and the Americas have recently implemented or proposed reforms to how they control cannabis use, thereby departing from traditional approaches of criminal prohibition that have dominated throughout most of the twentieth century. Given these policy developments and the widespread global use of cannabis, it is critically important to understand the possible risks associated with cannabis use in relation to major societal harms. Methods: This systematic review investigates the potential link between cannabis use and occupational injury. Consequently, it appraises all available current literature from five databases, following Cochrane and PRISMA guidelines. Results: Seven of the 16 reviewed studies show evidence supporting a positive association between cannabis use and occupational injury. One study shows evidence supporting a negative association and the remaining eight studies show no evidence of a significant relation. None of the studies assessed cannabis-related impairment. Only three of the reviewed studies show clear evidence that cannabis use preceded the occupational-injury event. Conclusion: The current body of evidence does not provide sufficient evidence to support the position that cannabis users are at increased risk of occupational injury. Further, the study quality assessment suggests significant biases in the extant literature are present due to potential confounding variables, selection of participants, and measurement of exposures and outcomes. Future high-quality evidence will be needed to elucidate the relation between cannabis use and occupational injury.

Violence and Cannabis Use: A Focused Review of a Forgotten Aspect in the Era of Liberalizing Cannabis

There has been a shift surrounding societal and legal perspectives on cannabis reflecting changing public attitudes towards the perceived safety and social acceptability of cannabis use. With cannabis liberalization internationally, the focus of most cannabis-related harms has been on effects with users themselves. Harm-to-others including injuries from violence have nevertheless been unfortunately largely overlooked. While studies remain heterogeneous, there is meta-analytical evidence pointing towards an association. The aims of this focused review are two-fold: (I) review the evidence from meta-analyses on the association between cannabis and violence; and (II) provide an overview of possible mechanisms relating cannabis use to violence. First, evidence from meta-analytical studies in youths, intimate partners, and individuals with severe mental disorders have shown that there is a global moderate association between cannabis use and violence, which is stronger in the latter more at-risk population. Preliminary data has even highlighted a potential dose-response relationship with larger effects in more frequent users. Although of importance, this subject has remained essentially forgotten as a public health concern. While literature remains inconclusive, data has suggested potential increases in cannabis use following liberalization policies. This may increase violent outcomes if the effect is directly related to the use of cannabis by means of its psychophysiological modifications. However, for the moment, the mechanisms associating cannabis use and violence remain to be clearly resolved. Considering the recency of policy changes on cannabis, further methodologically sound research using longitudinal designs should examine the effects that cannabis use may have on different forms of violence and the trends that emerge, while evaluating the effects of possible confounding factors (e.g. other substance use). In addition, as evidence-based research from meta-analyses have shown that cannabis use is associated with violence, measures must be taken to mitigate the risks.

Who consumes most of the cannabis in Canada? Profiles of cannabis consumption by quantity

AIM

To establish whether the population-level pattern of cannabis use by quantity is similar to the distributions previously reported for alcohol, in which a small subset of drinkers accounts for a majority of total population alcohol consumption.

METHOD

The current study pooled Waves 1-3 of the 2018 National Cannabis Survey (n = 18,900; 2584 past-three-month cannabis users), a set of stratified, population-based surveys designed to assess cannabis consumption and related behaviors in Canada. Each survey systematically measured self-reported cannabis consumption by quantity across seven of the major cannabis-product types. In order to enable the conversion of self-reported consumption of non-flower cannabis products into a standard joint equivalent (SJE: equal to 0.5 g of dried cannabis), we created conversion metrics for physical production equivalencies across cannabis products.

RESULTS

Similar to the findings in the alcohol literature, study results show that cannabis consumption is highly concentrated in a small subset of users: the upper 10% of cannabis users accounted for approximately two-thirds of all cannabis consumed in the country. Males reported consuming more cannabis by volume than females (approximately 60% versus 40%), with young males (15-34 years old) being disproportionately represented in the heaviest-using subgroups.

CONCLUSIONS

Most of the cannabis used in Canada is consumed by a relatively small population of very heavy cannabis users. Future research should attempt to identify the characteristics of the heaviest-using groups, as well as how population-level cannabis consumption patterns relate to the calculus of cannabis-related harms in society.

Cessation of cannabis use: A retrospective cohort study

Given recent findings of a worldwide increase in cannabis use, a better understanding of the factors associated with cannabis use is needed. Most previous studies have focused on factors that predict the initiation of cannabis use, but less is known about factors associated with cessation. The present study is a retrospective cohort study of 6467 current or former cannabis users aged 15 to 46 years (mean age 22.5, SD = 4.8). Data were collected via an online survey advertised in social media. All analyzed participants had used cannabis for at least three years. Approximately 16.3% (n = 1055) of the sample population had not used cannabis in the previous 12 months and were classified as quitters; all others (83.7%, n = 5412) reported at least monthly use. Cessation was predicted by older current age, being female, nonmigrant status, less sensation seeking, using psychological treatment, more peer cannabis use during youth and more negative first experience with cannabis. An additional predictor was a nonincrease in the frequency of cannabis use in the first three years of use, indicating that trajectories of cannabis use are set early on and might be used to identify risk groups for early preventive measures.

Unpacking the Longitudinal Associations between the Frequency of Substance Use, Substance Use Related Problems, and Academic Achievement among Adolescents

Previous research repeatedly observed associations between academic achievement and substance use during adolescence. However, the simple frequency of substance use was not differentiated from the emergence of substance use related problems, such as abuse and dependence. This study presents autoregressive cross-lagged models describing inter-relations between academic achievement, frequency of substance use, and substance use related problems among a sample of 1034 seventh graders (46% female; 83% White North Americans; Mage = 12.64 years, SD_age = 0.65) who participated in a four-year longitudinal study. The stability of measurement structure of frequency of substance use and substance use related problems was supported. Higher frequency of substance use and substance use related problems did not predict lower academic achievement. A higher academic achievement predicted a later increase in frequency of substance use and substance use related problems in boys, whereas a higher academic achievement predicted a lower frequency of substance use in girls. Although substance use related problems were mainly predicted by frequency of substance use, substance use can remain, nonetheless, non-problematic during adolescence.

Has illicit drug use become normalised in groups of Swedish youth? A latent class analysis of school survey data from 2012 to 2015

Background:

It is often assumed that illicit drug use has become normalised in the Western world, as evidenced for example by increased prevalence rates and drug-liberal notions in both socially advantaged and disadvantaged youth populations. There is accumulating research on the characteristics of young illicit drug users from high-prevalence countries, but less is known about the users in countries where use is less common. There is reason to assume that drug users in low-prevalence countries may be more disadvantaged than their counterparts in high-prevalence countries, and that the normalisation thesis perhaps does not apply to the former context.

Aim:

This article aims to explore to what extent such assertions hold true by studying the characteristics of young illicit drug users in Sweden, where prevalence is low and drug policy centres on zero tolerance.

Material and Method:

We draw on a subsample (n = 3374) of lifetime users of illicit drugs from four waves of a nationally representative sample of students in 9th and 11th grade (2012–2015). Latent class analysis (LCA) on ten indicators pertaining to illicit drug use identified four classes which we termed “Marijuana testers”, “Marijuana users”, “Cannabinoid users” and “Polydrug users”.

Findings:

Indications of social advantage/disadvantage such as peer drug use, early substance-use debut and truancy varied across groups, particularly between “Marijuana testers” (low scores) and “Polydrug users” (high scores).

Conclusions:

Our findings corroborate the idea that the majority of those who have used illicit drugs in the Swedish youth population have tried marijuana a few times only. We discuss whether or not the comparably large share of socially advantaged “Marijuana testers” in a comparably small sample of lifetime users can be interpreted as a sort of normalisation in a prohibitionist drug policy context.

Perceptions of the cognitive effects of cannabis use: A survey of neuropsychologists' beliefs

Introduction: Research evaluating the neuropsychological effects of cannabis has yielded mixed findings, with some studies finding cognitive deficits in cannabis users (primarily in learning and memory) and others finding no significant effects. It is important to understand how clinicians perceive this discrepancy in the empirical literature. However, no studies have assessed neuropsychologists' beliefs regarding the effects of cannabis on cognitive functioning. Thus, this study sought to evaluate how patient and cannabis-use factors influence neuropsychologists' perceptions of cannabis's cognitive effects. Method: Neuropsychologists (N = 261) read eight vignettes, each depicting cannabis users varying in age, gender, and cannabis-use history (frequency, duration, and recreational/medicinal use). Respondents rated the anticipated effects of cannabis in each vignette on nine cognitive domains. Mixed effects linear regression modeled the ratings of cognitive abilities as a function of neuropsychologist, neuropsychologists' training, vignette, patient age, gender, and frequency/duration/type of cannabis use, and treated neuropsychologist and vignette as random effects. Results: Duration of use had the most notable effect on neuropsychologists' ratings, with a small (0.1 to 0.2 SDs) yet statistically significant (p < .001) negative effect on each cognitive domain. Male gender and medicinal use also predicted lower cognitive ratings. Differences in ratings between neuropsychologists accounted for 73% of the total variability in each domain, whereas variability due to vignette alone was negligible (<1%). Conclusions: Results suggest that neuropsychologists believe that cannabis use results in broad but mild cognitive deficits, consistent with meta-analytic findings of active chronic cannabis users, particularly for males and for individuals using cannabis for medicinal purposes. Interestingly, neuropsychologists expected fewer cognitive effects in recreational cannabis users. Further, duration of use (rather than frequency) was believed to be the primary factor contributing to cognitive deficits.

What do we know about the pharmacotheraputic management of insomnia in cannabis withdrawal: A systematic review

BACKGROUND AND OBJECTIVES

Sleep disturbance is one of the hallmarks of cannabis withdrawal. Studies have indicated that treatment of this key symptom may facilitate abstinence. In the present paper we aim to provide a systematic review of the extant literature on pharmacological management of sleep disturbance associated with cannabis withdrawal.

METHOD

We conducted a systematic literature search across five electronic databases including PubMed, Psycinfo, MEDLINE, Cochrane review and Embase. Human studies using a pharmacological treatment for sleep disturbances associated with cannabis withdrawal were included. Review articles, case-series, open trials, posters, and editorials were excluded.

RESULTS

Seventeen publications, involving 562 participants, were included in this review. Major limitations involved small sample size, high dropout rate, methodological limitations, and heterogeneity of participants. Most of the studies were at high risk of bias, further downgrading the level of evidence. A meta-analysis was not performed due to lack of quantitative data, marked heterogeneity and low quality of the included studies.

CONCLUSION

There is not sufficient evidence for any of the reviewed treatment options. Methodological limitations in a majority of the studies rendered their findings preliminary. Of the twelve investigated pharmacological agents, Gabapentin, Lofexidine, Mirtazapine, Quetiapine, and Zolpidem showed some primary benefits for treatment of sleep difficulties associated with cannabis withdrawal; however, future prospective studies are required to confirm such results.

SCIENTIFIC SIGNIFICANCE

This review examines the current evidence for potential pharmacological options for treatment of cannabis withdrawal and associated sleep disturbance. It furthers our knowledge and provides groundwork for future research. (Am J Addict 2018;27:453-464).

Medical Marijuana and Marijuana Legalization

State-level marijuana liberalization policies have been evolving for the past five decades, and yet the overall scientific evidence of the impact of these policies is widely believed to be inconclusive. In this review we summarize some of the key limitations of the studies evaluating the effects of decriminalization and medical marijuana laws on marijuana use, highlighting their inconsistencies in terms of the heterogeneity of policies, the timing of the evaluations, and the measures of use being considered. We suggest that the heterogeneity in the responsiveness of different populations to particular laws is important for interpreting the mixed findings from the literature, and we highlight the limitations of the existing literature in providing clear insights into the probable effects of marijuana legalization.

Anatomy of a Joint: Comparing Self-Reported and Actual Dose of Cannabis and Tobacco in a Joint, and How These Are Influenced by Controlled Acute Administration

Introduction: Major gaps exist in the measurement of cannabis exposure. The accuracy of self-reported cannabis and tobacco dose per joint is poorly characterized and has never been investigated following acute cannabis/tobacco exposure. Using an innovative "Roll a Joint" paradigm, this study aims to (1) compare estimated and actual dose of cannabis and tobacco per joint at baseline and (2) examine the acute effects of cannabis and/or tobacco on estimated and actual dose. Materials and Methods: We investigated this by using a randomized, double-blind, placebo-controlled crossover 2 (active cannabis, placebo cannabis)×2 (active tobacco, placebo tobacco) design in a laboratory setting. Participants were 24 recreational cousers of cannabis and tobacco. At baseline, they were asked to measure out the amount of cannabis and tobacco they would put in an average joint for themselves (dose per joint). Then, on each of four drug administration sessions, participants were again asked to do this for a joint they would want to smoke "right now." Self-reported and actual amount was recorded (g). Results: At baseline, the estimated amount of cannabis per joint (0.28±0.23 g) was double the actual amount (0.14±0.12 g) (p=0.003, d=0.723). No difference emerged between estimated (0.43±0.25 g) and actual (0.35±0.15 g) (p=0.125) amount of tobacco per joint. Compared to placebo, active cannabis reduced the actual dose of both cannabis (p=0.035) and tobacco (p<0.001) they put in a joint. Participants accurately estimated this reduction for tobacco (p=0.014), but not for cannabis (p=0.680). Conclusions: Self-reported dose per joint is accurate for tobacco but dramatically overestimates cannabis exposure and therefore should be viewed with caution. Cannabis administration reduced the amount of cannabis and tobacco added to joints, suggesting a reduction in dose during a smoking session. The "Roll A Joint" paradigm should be implemented for better accuracy in assessing dose per joint.

Marijuana and Alcohol Use as Predictors of Academic Achievement: A Longitudinal Analysis Among Youth in the COMPASS Study

BACKGROUND

We tested the effect of initiating marijuana and alcohol use at varying frequencies on academic indices.

METHODS

In a sample of 26,475 grade 9-12 students with at least 2 years of linked longitudinal data from year 1 (Y1: 2012-2013), year 2 (Y2: 2013-2014), and year 3 (Y3: 2014-2015) of the COMPASS study, separate multinomial generalized estimating equations models tested the likelihood of responses to measures of academic goals, engagement, preparedness, and performance when shifting from never using alcohol or marijuana at baseline to using them at varying frequencies at follow -up.

RESULTS

Students who began using alcohol or marijuana were less likely to attend class regularly, complete their homework, achieve high marks, and value good grades, relative to their abstaining peers. Changing from abstaining to rare/sporadic-to-weekly drinking or rare/sporadic marijuana use predicted aspirations to continue to all levels of higher education, and initiating weekly marijuana use increased the likelihood of college ambitions, while more regular marijuana use reduced the likelihood of wanting to pursue graduate/professional degrees, over high school.

CONCLUSIONS

The importance of delaying or preventing substance use is evident in associations with student performance and engagement. The influence on academic goals varied by substance and frequency of initiated use.

Cannabis use and Drug Related Problems among Adolescents in 27 European Countries: The Utility of the Prevention Paradox

Aims

To study the prevalence of cannabis use and drug-related problems among European adolescents and the utility of the prevention paradox.

Methods

Survey data from the European School Survey Project on Alcohol and Other Drugs (ESPAD) in 2007 in the 27 countries with information about drug use and drug-related problems was used. We analysed the proportion of all drug-related problems that occurred in a high risk group and among others who had used cannabis in the previous 12 months. The cut-off for the high risk group was chosen to include 10-15 % of the most frequent cannabis users.

Results

The high risk groups accounted for a substantial, but a minority, of drug-related problems among boys as well as girls. A minority of those who had used cannabis reported any drug-related problem. The proportion of adolescents with drug-related problems and the average number of problems increased with frequency of cannabis use.

Conclusions

We find support for policy measures of more general character, supported by the prevention paradox. However, this does not exclude a policy supporting frequent drug users if they can be identified

Cannabis Epidemiology: A Selective Review

BACKGROUND

Globally, the most widely used set of compounds among the internationally regulated drugs is cannabis.

OBJECTIVE

To review evidence from epidemiological research on cannabis, organized in relation to this field's five main rubrics: quantity, location, causes, mechanisms, and prevention/ control.

METHOD

The review covers a selection of evidence from standardized population surveys, official statistics, and governmental reports, as well as published articles and books identified via MEDLINE, Web of Science, and Google Scholar as of July 2016.

RESULTS

In relation to quantity, an estimated 3% to 5% of the world population is thought to have tried a cannabis product, with at least one fairly recent use, mainly extra-medical and outside boundaries of prescribed use. Among cannabis users in the United States, roughly one in 7-8 has engaged in medical marijuana use. In relation to location, prevalence proportions reveal important variations across countries and between subgroups within countries. Regarding causes and mechanisms of starting to use cannabis, there is no compelling integrative and replicable conceptual model or theoretical formulation. Most studies of mechanisms have focused upon a 'gateway sequence' and person-to-person diffusion, with some recent work on disability-adjusted life years. A brief review of cannabis use consequences, as well as prevention and control strategies is also provided.

CONCLUSION

At present, we know much about the frequency and occurrence of cannabis use, with too little replicable definitive evidence with respect to the other main rubrics. Given a changing regulatory environment for cannabis products, new institutions such as an independent International Cannabis Products Safety Commission may be required to produce evidence required to weigh benefits versus costs. It is not clear that governmentsponsored research will be sufficient to meet consumer demand for balanced points of view and truly definitive evidence.

Keep off the grass? Cannabis, cognition and addiction

In an increasing number of states and countries, cannabis now stands poised to join alcohol and tobacco as a legal drug. Quantifying the relative adverse and beneficial effects of cannabis and its constituent cannabinoids should therefore be prioritized. Whereas newspaper headlines have focused on links between cannabis and psychosis, less attention has been paid to the much more common problem of cannabis addiction. Certain cognitive changes have also been attributed to cannabis use, although their causality and longevity are fiercely debated. Identifying why some individuals are more vulnerable than others to the adverse effects of cannabis is now of paramount importance to public health. Here, we review the current state of knowledge about such vulnerability factors, the variations in types of cannabis, and the relationship between these and cognition and addiction.

The Formation of Marijuana Risk Perception in a Population of Substance Abusing Patients

Risk perception has been shown to be protective with regard to marijuana use. Notably, the risk perception of marijuana in individuals with substance abuse problems varies significantly from that of the general public. Understanding how risk perception is formed in substance users could explain these differences and help predict the consequences of policy changes. Using this framework, we explored risk perception and its formation in a sample of substance abusing veterans. Semi-structured interviews were conducted with veterans who were receiving treatment for substance abuse. Interviews were recorded digitally, transcribed verbatim, and analyzed using inductive thematic analysis. A prominent perspective among the 31 participants was that marijuana is significantly different from other drugs because it is safe, not addictive, not associated with physical withdrawal, and has less overt behavioral effects than other substances. Many of these participants drew upon their own innocuous experiences with the drug in developing this perspective, more so than information from any other source. A contrasting narrative emphasized marijuana's capacity to cause negative social consequences, act as a gateway to the use of other, more harmful substances, and cause paranoia or worsen psychosis. In conclusion, individual experience with marijuana featured more prominently in informing risk perception than any other source of information. Our results and previous literature suggest that the significant disconnect between the individual experiences of substance users and the current clinical and legal policy towards marijuana may weaken the legitimacy of public policy or the authority of the medical community.

Are IQ and educational outcomes in teenagers related to their cannabis use? A prospective cohort study

There is much debate about the impact of adolescent cannabis use on intellectual and educational outcomes. We investigated associations between adolescent cannabis use and IQ and educational attainment in a sample of 2235 teenagers from the Avon Longitudinal Study of Parents and Children. By the age of 15, 24% reported having tried cannabis at least once. A series of nested linear regressions was employed, adjusted hierarchically by pre-exposure ability and potential confounds (e.g. cigarette and alcohol use, childhood mental-health symptoms and behavioural problems), to test the relationships between cumulative cannabis use and IQ at the age of 15 and educational performance at the age of 16. After full adjustment, those who had used cannabis ⩾ 50 times did not differ from never-users on either IQ or educational performance. Adjusting for group differences in cigarette smoking dramatically attenuated the associations between cannabis use and both outcomes, and further analyses demonstrated robust associations between cigarette use and educational outcomes, even with cannabis users excluded. These findings suggest that adolescent cannabis use is not associated with IQ or educational performance once adjustment is made for potential confounds, in particular adolescent cigarette use. Modest cannabis use in teenagers may have less cognitive impact than epidemiological surveys of older cohorts have previously suggested.

Associations of adolescent cannabis use with academic performance and mental health: A longitudinal study of upper middle class youth

BACKGROUND

There is a hypothesis that low socioeconomic status (SES) may explain the link between cannabis use and poorer academic performance and mental health. A key question, therefore, is whether adolescent cannabis use is associated with poorer academic performance and mental health in high SES communities where there is reduced potential for confounding.

METHODS

Youth (n=254) from an upper middle class community were followed prospectively through the four years of high school (from age 14/15 to age 17/18). Past-year frequency of cannabis use was assessed annually. Official school records of academic performance and self-reported mental health symptoms (externalizing and internalizing symptoms) were assessed in grades 9 and 12.

RESULTS

Persistent cannabis use across the four years of high school was associated with lower grade-point average (β=-0.18, p=.006), lower Scholastic Aptitude Test (SAT) score (β=-0.13, p=.038), and greater externalizing symptoms (β=0.29, p<.001) in 12th grade, but not with greater internalizing symptoms (β=0.04, p=.53). Moreover, persistent cannabis use was associated with lower grade-point average (β=-0.13, p=.014) and greater externalizing symptoms (β=0.24, p=.002) in 12th grade, even after controlling for 9th grade levels of these outcomes. Similar associations were observed for persistent alcohol and tobacco use. Effects for persistent cannabis use became non-significant after controlling for persistent alcohol and tobacco use, reflecting the difficulties of disentangling effects of cannabis from effects of alcohol and tobacco.

CONCLUSIONS

Low SES cannot fully explain associations between cannabis use and poorer academic performance and mental health.

Predicting Young Adult Degree Attainment by Late Adolescent Marijuana Use

PURPOSE

The purpose of this study was to assess whether infrequent and frequent marijuana use at age 19/20 years predicts receipt of educational degrees by the mid-20s, independent of confounding age 18 adolescent risk factors.

METHODS

Data were from the Monitoring the Future study, an annual nationally representative survey of high school seniors followed into adulthood. Thirteen cohorts (1990-2002) of high school seniors were followed longitudinally to their mid-20s (n = 4,925; 54% female). We used logistic regression and propensity score matching with successive inclusion of age 18 risk factors and substance use to compare age 19/20 frequent marijuana users (six or more occasions in past 30 days) to nonusers, frequent users to infrequent users (1-6 occasions), and infrequent users to nonusers on their likelihood of degree attainment by the mid-20s.

RESULTS

Frequent marijuana users were less likely than infrequent users and nonusers to earn bachelor's degrees, even after controlling for a host of age 18 risk factors (e.g., family socioeconomic background, academic performance, educational expectations, truancy). However, these differences were reduced in magnitude to statistical nonsignificance when we controlled for age 18 substance use. Across analyses, the proportion reaching this educational milestone did not differ significantly between infrequent users and nonusers.

CONCLUSIONS

Results support a growing body of work suggesting that frequent marijuana use predicts a lower likelihood of postsecondary educational attainment, and this difference may originate during secondary school.

Effects of marijuana use on impulsivity and hostility in daily life

BACKGROUND

Marijuana use is increasingly prevalent among young adults. While research has found adverse effects associated with marijuana use within experimentally controlled laboratory settings, it is unclear how recreational marijuana use affects day-to-day experiences in users. The present study sought to examine the effects of marijuana use on within-person changes in impulsivity and interpersonal hostility in daily life using smartphone administered assessments.

METHODS

Forty-three participants with no substance dependence reported on their alcohol consumption, tobacco use, recreational marijuana use, impulsivity, and interpersonal hostility over the course of 14 days. Responses were analyzed using multilevel modeling.

RESULTS

Marijuana use was associated with increased impulsivity on the same day and the following day relative to days when marijuana was not used, independent of alcohol use. Marijuana was also associated with increased hostile behaviors and perceptions of hostility in others on the same day when compared to days when marijuana was not used. These effects were independent of frequency of marijuana use or alcohol use. There were no significant effects of alcohol consumption on impulsivity or interpersonal hostility.

CONCLUSIONS

Marijuana use is associated with changes in impulse control and hostility in daily life. This may be one route by which deleterious effects of marijuana are observed for mental health and psychosocial functioning. Given the increasing prevalence of recreational marijuana use and the potential legalization in some states, further research on the potential consequences of marijuana use in young adults' day-to-day life is warranted.

Three-Year Course of Cannabis Dependence and Prediction of Persistence

AIMS

To examine the course and the predictors of the persistence of cannabis dependence.

METHODS

Through cannabis outlets and chain referral, a prospective enriched community cohort of 207 young adults (aged 18-30) with DSM-IV cannabis dependence at baseline (T0) was formed and followed-up after 1.5 (T1) and 3 (T2) years. The presence of cannabis dependence, cannabis-related problems, functional impairment and treatment was assessed using the Composite International Diagnostic Interview (CIDI 3.0) and the Sheehan Disability Scale (SDS). Predictors of persistence were lifetime cannabis abuse and dependence symptoms, cannabis use characteristics, distant vulnerability factors (e.g. childhood adversity, family history of psychological/substance use problems, impulsivity, mental disorders), and proximal stress factors (recent life events, social support).

RESULTS

Four groups were distinguished: persistent dependent (DDD: 28.0%), stable non-persistent (DNN: 40.6%), late non-persistent (DDN: 17.9%) and recurrent dependent (DND: 13.5%). At T2, persisters (DDD) reported significantly more (heavy) cannabis use and cannabis problems than non-persisters (DNN/DDN/DND). Treatment seeking for cannabis-related problems was rare, even among persisters (15.5%). The number (OR = 1.23 (1.03-1.48)) and type ('role impairment' OR = 2.85 (1.11-7.31), 'use despite problems' OR = 2.34 (1.15-4.76)) of lifetime cannabis abuse/dependence symptoms were the only independent predictors of persistence with a total explained variance of 8.8%.

CONCLUSIONS

Persistence of cannabis dependence in the community is low, difficult to predict, and associated with a negative outcome. The substantial proportion of stable non-persisters suggests that screening and monitoring or low-threshold brief interventions may suffice for many non-treatment-seeking cannabis-dependent people. However, those with many lifetime abuse/dependence symptoms may benefit from more intensive interventions.

Marijuana use and intoxication among daily users: an intensive longitudinal study

BACKGROUND

Most of the harm from marijuana use is experienced by daily users. Despite this, there has not been a detailed prospective description of daily marijuana use.

METHODS

We recruited daily marijuana users (n=142) by internet ads, Craigslist, flyers, etc. Participants were mostly women (58%) with a mean age of 33 and 47% were minorities. Participants called an Interactive Voice Response phone system to report marijuana and other drug use daily for 3months.

RESULTS

Participants averaged using marijuana 3.2 times per day. Almost all participants used multiple modes of delivery during the study. Bongs/vaporizers/pipes were the most common mode of use (45% of uses). Day-to-day variability in amount of use was relatively small. The median rating of intoxication was 3.8 on a 0-6 scale with no intoxication reported on 1% of days and severe intoxication on 24% of days. The large majority binge drank (71%) or used tobacco (73%). Fifteen during-study variables were associated with the frequency of marijuana use; running out of marijuana and social setting were the strongest correlates. Retrospective reports of "usual" use at study entry were often significantly different than daily reports of use during the study.

CONCLUSIONS

This is the first detailed prospective description of daily marijuana use. Most users used multiple times/day, used multiple modes to administer marijuana, were often intoxicated, and under-reported high rates of using alcohol and tobacco. The frequency of marijuana use was especially influenced by social factors. These results will help future studies better describe daily marijuana use.

The role of leisure and delinquency in frequent cannabis use and dependence trajectories among young adults

BACKGROUND

The link between leisure and cannabis use has been widely studied, but less so for young adults, and rarely with a focus on frequent cannabis use. Also, little is known about how changes in leisure develop over time and how they are related to transitions in cannabis use and dependence.

METHOD

As part of a 3-year longitudinal project, in a qualitative study 47 frequent male and female young adult cannabis users with (n=23) and without (n=24) dependence at baseline were interviewed in-depth after 1.5 and 3 years.

RESULTS

Frequent cannabis users (at baseline ≥3 days per week in the past 12 months) are involved in similar leisure activities as the general young adult population and live rather conventional lives, generally away from a delinquent subculture. They mostly regulate their cannabis use to leisure time, to enhance other leisure activities, including socialising and video gaming. While they often give precedence to responsibilities (e.g. work and study), dependent and non-dependent users differed in whether they actively adapted their leisure activities to their cannabis use, or their cannabis use to their leisure time. Both types of and time spent on leisure activities were associated with transitions in use and dependence.

CONCLUSIONS

While our findings generally support the normalisation thesis, it is questionable whether frequent but non-problematic cannabis use is socially accepted in wider society. This study also questions the diagnostic dependence vs. non-dependence dichotomy, and adds finer distinctions to the concept of cannabis dependence. Implications for prevention and treatment include facilitating structured spending of leisure time (e.g. sports), and targeting frequent users who spent much leisure time video gaming at home.

An Examination of Marijuana Use Among a Vulnerable Population in Canada

OBJECTIVES

Although the perceived risk of cannabis has decreased over the last few years, the contribution of marijuana use to the burden of disease on society is significant. Globally, Indigenous peoples have rates of marijuana use that are significantly higher than that of the general population. Understanding patterns of use is fundamental to developing appropriate policy and programming strategies to improve health and well-being.

METHODS

This study examined the characteristics of respondents who had ever been frequent marijuana users (used more than once a week), among a cross-sectional sample of 340 people, aged 18 and over, from Kettle and Stony Point First Nation in Ontario, Canada. The research incorporated Aboriginal-specific measures, examining issues related to colonialism and racism. Logistic regression models were used to assess the extent that sociodemographic variables, body mass index, mental health (depression, anxiety), licit substance use (alcohol and tobacco), Historical Loss Scale, Childhood Trauma Scale, and Measure of Indigenous Racism Experience (MIRE) Interpersonal Racism Scale predicted ever having been a frequent marijuana user.

RESULTS

Aboriginal-specific issues were not associated with marijuana use nor was marijuana use related to depression or anxiety. However, ever engaging in frequent marijuana use was reported by more than half of the sample and associated with being younger, male, and a smoker.

CONCLUSIONS

The high prevalence of frequent marijuana use (53.2 %) suggests normalization of the substance that may indicate a potentially large public health problem.

Cross-sectional and prospective relation of cannabis potency, dosing and smoking behaviour with cannabis dependence: an ecological study

BACKGROUND AND AIMS

Increased delta-9-tetrahydrocannabinol (THC) concentrations in cannabis may lead to higher THC exposure, cannabis dependence and treatment need, but users may also adapt the actual intake of THC through reduced inhalation of THC containing smoke (titration). We investigated whether consumers of stronger cannabis use less cannabis per joint or inhale less smoke than those using less potent cannabis and whether these factors predict cannabis dependence severity.

METHODS

Heavy cannabis users (n = 98) brought their own cannabis, rolled a joint and smoked it ad libitum in a naturalistic setting. We analysed the content of the joint, its association with smoking behaviour and the cross-sectional and prospective (1.5-year follow-up) relations between smoking behaviour and cannabis dependence severity (total number of DSM-IV dependence symptoms).

RESULTS

THC concentration in cannabis (range 1.10-24.70%) was correlated positively with cannabis dose per joint (b = 0.008, P = 0.01), but the resulting THC concentration per joint (range 0.24-15.72%) was associated negatively with inhalation volume (b = -0.05, P = 0.03). Smoking behaviour measures (number of puffs, inhaled volume, reduction of puff volume and puff duration while smoking) predicted follow-up dependence severity, independently of baseline dependence severity and monthly THC dose (number of joints × cannabis dose × cannabis THC concentration). Monthly THC dose only predicted follow-up dependence severity when unadjusted for baseline severity.

CONCLUSIONS

Cannabis users titrate their delta-9-tetrahydrocannabinol intake by inhaling lower volumes of smoke when smoking strong joints, but this does not fully compensate for the higher cannabis doses per joint when using strong cannabis. Thus, users of more potent cannabis are generally exposed to more delta-9-tetrahydrocannabinol. Smoking behaviour appears to be a stronger predictor for cannabis dependence severity than monthly delta-9-tetrahydrocannabinol dose.

The link between dopamine function and apathy in cannabis users: an [18F]-DOPA PET imaging study

RATIONALE

Cannabis is the most widely used illicit drug in the world, and regular use has been associated with reduced motivation, i.e. apathy. Regular long-term cannabis use has been associated with reduced dopamine synthesis capacity. The mesolimbic dopaminergic system mediates the processing of incentive stimuli by modifying their motivational value, which in turn is modulated by endocannabinoid signalling. Thus, it has been proposed that dopaminergic dysfunction underlies the apathy associated with chronic cannabis use.

OBJECTIVES

The aim of this study was to examine the relationship between dopaminergic function and subjective apathy in cannabis users.

METHODS

We measured dopamine synthesis capacity (indexed as the influx rate constant K i(cer)) via 3,4-dihydroxy-6-[(18)F]-fluoro-l-phenylalanine positron emission tomography and subjective apathy using the self-rated Apathy Evaluation Scale (AES-S) in 14 regular cannabis users.

RESULTS

All subjects scored in excess of 34 points on the AES-S (median [interquartile range] 59.5 [7.5]), indicative of significant apathy based on normative data. K i (cer) was inversely correlated to AES-S score in the whole striatum and its associative functional subdivision (Spearman's rho = -0.64, p = 0.015 [whole striatum]; rho = -0.69, p = 0.006 [associative]) but not in the limbic or sensorimotor striatal subdivisions. There were no significant relationships between AES-S and current cannabis consumption (rho = 0.28, p = 0.34) or age of first cannabis use (rho = 0.25, p = 0.40).

CONCLUSIONS

These findings indicate that the reduction in striatal dopamine synthesis capacity associated with chronic cannabis use may underlie reduced reward sensitivity and a motivation associated with chronic cannabis use.

Problems with the identification of 'problematic' cannabis use: examining the issues of frequency, quantity, and drug use environment

Considerable recent attention has focused on how harmful or problematic cannabis use is defined and understood in the literature and put to use in clinical practice. The aim of the current study is to review conceptual and measurement shortcomings in the identification of problematic cannabis use, drawing on the WHO ASSIST instrument for specific examples. Three issues with the current approach are debated and discussed: (1) the identification of problematic cannabis use disproportionately relies on measures of the frequency of cannabis consumption rather than the harms experienced; (2) the quantity consumed on a typical day is not considered when assessing problematic use, and (3) screening tools for problematic use employ a 'one-size-fits-all approach' and fail to reflect on the drug use context (networks and environment). Our commentary tackles each issue, with a review of relevant literature coupled with analyses of two Canadian data sources--a representative sample of the Canadian adult population and a smaller sample of adult, regular, long-term cannabis users from four Canadian cities--to further articulate each point. This article concludes with a discussion of appropriate treatment interventions and approaches to reduce cannabis-related harms, and offers suggested changes to improve the measurement of problematic cannabis use.

Predicting the transition from frequent cannabis use to cannabis dependence: a three-year prospective study

BACKGROUND

Frequent cannabis users are at high risk of dependence, still most (near) daily users are not dependent. It is unknown why some frequent users develop dependence, whereas others do not. This study aims to identify predictors of first-incidence DSM-IV cannabis dependence in frequent cannabis users.

METHODS

A prospective cohort of frequent cannabis users (aged 18-30, n=600) with baseline and two follow-up assessments (18 and 36 months) was used. Only participants without lifetime diagnosis of DSM-IV cannabis dependence at baseline (n=269) were selected. Incidence of DSM-IV cannabis dependence was established using the Composite International Diagnostic Interview version 3.0. Variables assessed as potential predictors of the development of cannabis dependence included sociodemographic factors, cannabis use variables (e.g., motives, consumption habits, cannabis exposure), vulnerability factors (e.g., childhood adversity, family history of mental disorders or substance use problems, personality, mental disorders), and stress factors (e.g., life events, social support).

RESULTS

Three-year cumulative incidence of cannabis dependence was 37.2% (95% CI=30.7-43.8%). Independent predictors of the first incidence of cannabis dependence included: living alone, coping motives for cannabis use, number and type of recent negative life events (major financial problems), and number and type of cannabis use disorder symptoms (impaired control over use). Cannabis exposure variables and stable vulnerability factors did not independently predict first incidence of cannabis dependence.

CONCLUSIONS

In a high risk population of young adult frequent cannabis users, current problems are more important predictors of first incidence cannabis dependence than the level and type of cannabis exposure and stable vulnerability factors.

Validation of self-reported cannabis dose and potency: an ecological study

AIMS

To assess the reliability and validity of self-reported cannabis dose and potency measures.

DESIGN

Cross-sectional study comparing self-reports with objective measures of amount of cannabis and delta-9-tetrahydrocannabinol (THC) concentration.

SETTING

Ecological study with assessments at participants' homes or in a coffee shop.

PARTICIPANTS

Young adult frequent cannabis users (n = 106) from the Dutch Cannabis Dependence (CanDep) study.

MEASUREMENTS

The objectively measured amount of cannabis per joint (dose in grams) was compared with self-reported estimates using a prompt card and average number of joints made from 1 g of cannabis. In addition, objectively assessed THC concentration in the participant's cannabis was compared with self-reported level of intoxication, subjective estimate of cannabis potency and price per gram of cannabis.

FINDINGS

Objective estimates of doses per joint (0.07-0.88 g/joint) and cannabis potency (1.1-24.7%) varied widely. Self-reported measures of dose were imprecise, but at group level, average dose per joint was estimated accurately with the number of joints made from 1 g [limit of agreement (LOA) = -0.02 g, 95% confidence interval (CI) = -0.29; 0.26], whereas the prompt card resulted in serious underestimation (LOA = 0.14 g, 95% CI = -0.10; 0.37). THC concentration in cannabis was associated with subjective potency ['average' 3.77% (P = 0.002) and '(very) strong' 5.13% more THC (P < 0.001) than '(very) mild' cannabis] and with cannabis price (about 1% increase in THC concentration per euro spent on 1 g of cannabis, P < 0.001), but not with level of intoxication.

CONCLUSIONS

Self-report measures relating to cannabis use appear at best to be associated weakly with objective measures. Of the self-report measures, number of joints per gram, cannabis price and subjective potency have at least some validity.

Mental health differences between frequent cannabis users with and without dependence and the general population

AIMS

To compare the prevalence of mental disorders between frequent cannabis users with and without dependence and the general population.

DESIGN

Cross-sectional comparison of interview data.

SETTING

Enriched community sample of frequent cannabis users and a representative sample of non-users and non-frequent users from the general population.

PARTICIPANTS

A total of 521 young adult (aged 18-30 years) frequent cannabis users, 252 of whom were with DSM-IV cannabis dependence (D+) and 269 without DSM-IV cannabis dependence (D-), and 1072 young adults from the general population.

MEASUREMENTS

Multinomial logistic regression was used to compare groups regarding the presence of DSM-IV mental disorders. Detailed measures of cannabis use, childhood adversity and other substance use were considered confounders.

FINDINGS

Compared with the general population, externalizing disorders were more prevalent in D- [odds ratio (OR) = 8.91, P < 0.001] and most prevalent in D+ (OR = 17.75, P < 0.001), but internalizing disorders were associated only with D+ (mood OR = 4.15, P < 0.001; anxiety OR = 2.20, P = 0.002). Associations were attenuated (and often became non-significant) after correction for childhood adversity and substance use other than cannabis. However, the prevalence of mental disorders remained higher in D+ compared with D- (OR = 2.40, P < 0.001), although cannabis use patterns were remarkably similar.

CONCLUSIONS

Cannabis use patterns, childhood adversity and the use of other substances are similar in dependent and non-dependent frequent cannabis users. With the exception of more externalizing disorders, the mental health condition of non-dependent frequent cannabis users is similar to that of the general population, whereas it is worse in dependent frequent cannabis users.

Alcohol and marijuana use in the context of tobacco dependence treatment: impact on outcome and mediation of effect

INTRODUCTION

Alcohol and marijuana are among the most commonly used substances together with tobacco worldwide, but their relationship to smoking cessation is unclear. Although alcohol use decreases the likelihood of abstinence from tobacco, mechanisms of this effect have not been identified. Moreover, a small literature has yielded inconsistent findings regarding the effect of marijuana use on tobacco dependence treatment outcome. The aims of this study were to test increased positive-reinforcement smoking urge as a mediator of the relationship between alcohol and cigarette use and evaluate the impact of marijuana use on abstinence from tobacco.

METHODS

Participants were adult cigarette smokers (N = 739) from 3 randomized clinical trials of smoking cessation treatment. Alcohol consumption and marijuana use were assessed at pretreatment and postcessation. Biochemically verified, 7-day point prevalence smoking abstinence was determined at Weeks 12, 24, 36, and 52, as were urges to smoke as measured by the Questionnaire of Smoking Urges.

RESULTS

Increased positive-reinforcement urge mediated the effect of postcessation alcohol use on smoking abstinence. Although pretreatment alcohol use was associated with a decreased likelihood of abstinence from tobacco, increased positive-reinforcement urge did not account for this relationship. Marijuana use was not associated with abstinence from tobacco.

CONCLUSIONS

Smoking cessation treatments should provide those who drink during a quit attempt techniques designed to mitigate positive-reinforcement urge to smoke. Additional research is needed to determine how pretreatment alcohol consumption exerts its effect on cigarette use. Modifying the use of marijuana might not be critical to the success of tobacco interventions.

Cannabis and social welfare assistance: a longitudinal study

AIMS

To investigate associations between cannabis use and subsequent receipt of social welfare assistance.

DESIGN, SETTING AND PARTICIPANTS

The Young in Norway Longitudinal Study. A population-based Norwegian sample (n = 2606) was followed-up from adolescence to late 20s. Self-report data were merged with data from national registers.

MEASUREMENTS

Data were extracted on the use of alcohol, tobacco and cannabis and other illegal substances. Information was also retrieved on socio-demographic and family factors, academic achievement, conduct problems and mental health. National registers provided data on social welfare assistance, educational level and crime statistics.

FINDINGS

We observed prospective bivariate associations between increasing levels of cannabis use and subsequent social welfare assistance (P < 0.0001). The associations were reduced after adjusting for a range of potentially confounding factors, but remained significant. Frequent cannabis users were at highly increased risk for subsequently receiving social welfare assistance. At 28 years, those with 50+ times cannabis use during the previous 12 months and had an odds ratio of 9.3 (95% confidence interval: 4.3-20.1) for receiving social welfare assistance in the following 2-year span. Users of cannabis also had longer periods of receiving social welfare assistance than others (P < 0.0001) and were less likely to leave the welfare assistance system (P < 0.0001).

CONCLUSIONS

In Norway the use of cannabis is linked with subsequent receipt of social welfare assistance whether the consequences are related to use of the substance per se, or to cultural factors and the illegal status of the cannabis. Future research should attempt to understand the interactions of factors behind these associations.

The Dutch Cannabis Dependence (CanDep) study on the course of frequent cannabis use and dependence: objectives, methods and sample characteristics

This paper presents an overview of the prospective cohort design of the Dutch Cannabis Dependence (CanDep) study, which investigates (i) the three-year natural course of frequent cannabis use (≥ three days per week in the past 12 months) and cannabis dependence; and (ii) the factors involved in the transition from frequent non-dependent cannabis use to cannabis dependence, and remission from dependence. Besides its scientific relevance, this knowledge may contribute to improve selective and indicated prevention, early detection, treatment and cannabis policies. The secondary objectives are the identification of factors related to treatment seeking and the validation of self report measures of cannabis use. Between September 2008 and April 2009, baseline data were collected from 600 frequent cannabis users with an average age of 22.1 years, predominantly male (79.3%) and an average cannabis use history of 7.1 years; 42.0% fulfilled a (12-month DSM-IV) diagnosis of cannabis dependence. The response rate was 83.7% after the first follow up at 18 months. The second and last follow-up is planned at 36 months. Computer assisted personal interviews (CAPI) were conducted which covered: cannabis use (including detailed assessments of exposure, motives for use and potency preference); use of other substances; DSM-IV internalizing and externalizing mental disorders; treatment seeking; personality; life events; social support and social functioning.