Changes in cigarette and alcohol use during cannabis abstinence

The underrepresentation of racial/ethnic minorities in research on co-use of nicotine, alcohol, and/or cannabis via ecological momentary assessment methods: A narrative review

BACKGROUND

Co-use of nicotine, alcohol and/or cannabis is common among adults in the United States. Co-use may represent greater addiction severity than single substance use. Recent studies have examined the extent to which the frequency, order, simultaneity, motivations, and contextual factors associated with co-use differ from that of single use. Co-use has become prevalent among racial/ethnic minority individuals who exhibit distinct co-use patterns and related outcomes; however, most of these studies rely on cross-sectional or sparse longitudinal observations. Ecological momentary assessment (EMA) can illuminate such patterns and associations with time-varying contexts. This review summarizes EMA studies on co-use published from 2008 to 2023 involving racial/ethnic minority individuals and point to gaps. Our review addresses: 1) whether use of one substance leads to substitution or complementary use of another, 2) whether antecedents/contexts differ by co-use patterns and minority status, and 3) what consequences of co-use have been documented across co-use patterns or minority status.

METHODS

Search results yielded 465 articles, with 33 meeting inclusion criteria. We extracted study-level characteristics and synthesized the findings.

RESULTS

The findings largely focused on co-use patterns, categories of co-use, proximal antecedents and contexts, and consequences. Variations by minority status were rarely examined; few examined acute effects of unique experiences that may contribute to co-use among racial/ethnic minority adults.

CONCLUSIONS

The EMA literature on co-use is burgeoning in recent years and supports complementary hypothesis. More research to capture time-intensive data on experiences to contextualize the co-use among racial/ethnic minority groups with greater diversity in race/ethnicity is warranted.

Profiles of cannabis users and impact on cannabis cessation

Although cannabis was legalized in Canada in 2018 and is one of the most used substances in Canada, few studies have examined how individuals with different patterns of cannabis use differ in their attempts to decrease or abstain from cannabis. The current study examined how groups of cannabis users, which were formed on the basis of demographic characteristics, substance use patterns, mental health symptoms, and self-reported quality of life differed on their experiences with cannabis cessation. A sample of 147 Canadian adult participants who had attempted to decrease or quit cannabis were recruited from the community (n = 84, 57.14%) and crowdsourcing (n = 63, 42.86%). Four profiles of cannabis users emerged using a Latent Profile Analysis: low-risk (n = 62, 42.18%), rapidly escalating high-risk (n = 40, 27.21%), long-term high severity (n = 35, 23.81%), and long-term lower severity (n = 10, 6.80%). Individuals in the rapidly escalating profile had attempted to decrease their cannabis use more times compared to other profiles. More participants in the long-term high severity group found their use stayed the same or got worse after their last cessation attempt, compared to the low-risk group where more individuals indicated their use stopped. The results of the current study indicate that cannabis users differ in their attempts at reducing or ceasing cannabis use and that they may benefit from different intensity of cannabis interventions.

Generalized genetic liability to substance use disorders

Lifetime and temporal co-occurrence of substance use disorders (SUDs) is common and compared with individual SUDs is characterized by greater severity, additional psychiatric comorbidities, and worse outcomes. Here, we review evidence for the role of generalized genetic liability to various SUDs. Coaggregation of SUDs has familial contributions, with twin studies suggesting a strong contribution of additive genetic influences undergirding use disorders for a variety of substances (including alcohol, nicotine, cannabis, and others). GWAS have documented similarly large genetic correlations between alcohol, cannabis, and opioid use disorders. Extending these findings, recent studies have identified multiple genomic loci that contribute to common risk for these SUDs and problematic tobacco use, implicating dopaminergic regulatory and neuronal development mechanisms in the pathophysiology of generalized SUD genetic liability, with certain signals demonstrating cross-species and translational validity. Overlap with genetic signals for other externalizing behaviors, while substantial, does not explain the entirety of the generalized genetic signal for SUD. Polygenic scores (PGS) derived from the generalized genetic liability to SUDs outperform PGS for individual SUDs in prediction of serious mental health and medical comorbidities. Going forward, it will be important to further elucidate the etiology of generalized SUD genetic liability by incorporating additional SUDs, evaluating clinical presentation across the lifespan, and increasing the granularity of investigation (e.g., specific transdiagnostic criteria) to ultimately improve the nosology, prevention, and treatment of SUDs.

Cannabis cravings predict cigarette use in schizophrenia: a secondary analysis from two cannabis abstinence studies

CLINICAL TRIAL NAME

Effects of Repetitive Transcranial Magnetic Stimulation (rTMS) on Cannabis Use and Cognitive Outcomes in SchizophreniaURL: www.clinicaltrials.gov; Registration Number: NCT03189810.

Effects of combined use of alcohol and delta-9-tetrahydrocannibinol on working memory in Long Evans rats

The increase in social acceptance and legalization of cannabis over the last several years is likely to increase the prevalence of its co-use with alcohol. In spite of this, the potential for effects unique to co-use of these drugs, especially in moderate doses, has been studied relatively infrequently. We addressed this in the current study using a laboratory rat model of voluntary drug intake. Periadolescent male and female Long-Evans rats were allowed to orally self-administer ethanol, Δ9-tetrahydrocannibinol (THC), both drugs, or their vehicle controls from postnatal day (P) 30 to P47. They were subsequently trained and tested on an instrumental behavior task that assesses attention, working memory and behavioral flexibility. Similar to previous work, consumption of THC reduced both ethanol and saccharin intake in both sexes. Blood samples taken 14 h following the final self-administration session revealed that females had higher levels of the THC metabolite THC-COOH. There were modest effects of THC on our delayed matching to position (DMTP) task, with females exhibiting reduced performance compared to their control group or male, drug using counterparts. However, there were no significant effects of co-use of ethanol or THC on DMTP performance, and drug effects were also not apparent in the reversal learning phase of the task when non-matching to position was required as the correct response. These findings are consistent with other published studies in rodent models showing that use of these drugs in low to moderate doses does not significantly impact memory or behavioral flexibility following a protracted abstinence period.

Alcohol, cannabis, and nicotine use have distinct associations with COVID-19 pandemic-related experiences: An exploratory Bayesian network analysis across two timepoints

BACKGROUND

Substance use trends during the COVID-19 pandemic have been extensively documented. However, relatively less is known about the associations between pandemic-related experiences and substance use.

METHOD

In July 2020 and January 2021, a broad U.S. community sample (N = 1123) completed online assessments of past month alcohol, cannabis, and nicotine use and the 92-item Epidemic-Pandemic Impacts Inventory, a multidimensional measure of pandemic-related experiences. We examined links between substance use frequency, and pandemic impact on emotional, physical, economic, and other key domains, using Bayesian Gaussian graphical networks in which edges represent significant associations between variables (referred to as nodes). Bayesian network comparison approaches were used to assess the evidence of stability (or change) in associations between the two timepoints.

RESULTS

After controlling for all other nodes in the network, multiple significant edges connecting substance use nodes and pandemic-experience nodes were observed across both time points, including positive- (r range 0.07-0.23) and negative-associations (r range -0.25 to -0.11). Alcohol was positively associated with social and emotional pandemic impacts and negatively associated with economic impacts. Nicotine was positively associated with economic impact and negatively associated with social impact. Cannabis was positively associated with emotional impact. Network comparison suggested these associations were stable across the two timepoints.

CONCLUSION

Alcohol, nicotine, and cannabis use had unique associations to a few specific domains among a broad range of pandemic-related experiences. Given the cross-sectional nature of these analyses with observational data, further investigation is needed to identify potential causal links.

Effects of combined use of alcohol and delta-9-tetrahydrocannibinol on working memory in Long Evans rats

The increase in social acceptance and legalization of cannabis over the last several years is likely to increase the prevalence of its co-use with alcohol. In spite of this, the potential for effects unique to co-use of these drugs, especially in moderate doses, has been studied relatively infrequently. We addressed this in the current study using a laboratory rat model of voluntary drug intake. Periadolescent male and female Long-Evans rats were allowed to orally self-administer ethanol, Î" 9 -tetrahydrocannibinol (THC), both drugs, or their vehicle controls from postnatal day (P) 30 to P47. They were subsequently trained and tested on an instrumental behavior task that assesses attention, working memory and behavioral flexibility. Similar to previous work, consumption of THC reduced both ethanol and saccharin intake in both sexes. Blood samples taken 14h following the final self-administration session revealed that females had higher levels of the THC metabolite THC-COOH. There were modest effects of THC on our delayed matching to position (DMTP) task, with females exhibiting reduced performance compared to their control group or male, drug using counterparts. However, there were no significant effects of co-use of ethanol or THC on DMTP performance, and drug effects were also not apparent in the reversal learning phase of the task when non-matching to position was required as the correct response. These findings are consistent with other published studies in rodent models showing that use of these drugs in low to moderate doses does not significantly impact memory or behavioral flexibility following a protracted abstinence period.

Contingency Management for Treatment of Cannabis Use Disorder in Co-Occurring Mental Health Disorders: A Systematic Review

Amongst individuals with a mental health disorder, a comorbid diagnosis of cannabis use disorder (CUD) is associated with numerous adverse consequences, including more severe symptom profiles, poorer treatment response, and reduced psychosocial functioning. Contingency management (CM), a method to specifically reinforce target behavior attainment (e.g., substance use abstinence), may provide an effective intervention in treating cannabis use in patients with a dual diagnosis of CUD and a mental health disorder. A systematic search examining the effects of CM on cannabis use, clinical, cognitive, and psychosocial outcomes in patients with a mental health disorder on PubMed, PsycINFO, and EMBASE databases up to November 2022 was performed. Six studies met inclusion criteria for our review. We found CM to be efficacious in producing cannabis use reductions and abstinence amongst individuals with a psychotic-spectrum or major depressive disorder. Additional longitudinal studies with larger sample sizes, other psychiatric populations, and longer follow-up periods are needed to evaluate the sustained effects of CM.

Pattern of predictive features of continued cannabis use in patients with recent-onset psychosis and clinical high-risk for psychosis

Continued cannabis use (CCu) is an important predictor for poor long-term outcomes in psychosis and clinically high-risk patients, but no generalizable model has hitherto been tested for its ability to predict CCu in these vulnerable patient groups. In the current study, we investigated how structured clinical and cognitive assessments and structural magnetic resonance imaging (sMRI) contributed to the prediction of CCu in a group of 109 patients with recent-onset psychosis (ROP). We tested the generalizability of our predictors in 73 patients at clinical high-risk for psychosis (CHR). Here, CCu was defined as any cannabis consumption between baseline and 9-month follow-up, as assessed in structured interviews. All patients reported lifetime cannabis use at baseline. Data from clinical assessment alone correctly classified 73% (p < 0.001) of ROP and 59 % of CHR patients. The classifications of CCu based on sMRI and cognition were non-significant (ps > 0.093), and their addition to the interview-based predictor via stacking did not improve prediction significantly, either in the ROP or CHR groups (ps > 0.065). Lower functioning, specific substance use patterns, urbanicity and a lack of other coping strategies contributed reliably to the prediction of CCu and might thus represent important factors for guiding preventative efforts. Our results suggest that it may be possible to identify by clinical measures those psychosis-spectrum patients at high risk for CCu, potentially allowing to improve clinical care through targeted interventions. However, our model needs further testing in larger samples including more diverse clinical populations before being transferred into clinical practice.

Patterns of Cannabis and Alcohol Co-Use: Substitution Versus Complementary Effects

PURPOSE

The purpose of this review is to discuss the literature regarding the concurrent use (co-use) of alcohol and cannabis and competing hypotheses as to whether cannabis acts as a substitute for (i.e., replacing the effects of alcohol, resulting in decreased use) or a complement to (i.e., used to enhance the effects of alcohol, resulting in increased use) alcohol. The impact of cannabis use on alcohol-related outcomes has received increased attention in the wake of ongoing legalization of cannabis for both medical and recreational purposes. Evidence for both hypotheses exists in the literature across a broad range of data collection methods and samples and is carefully reviewed here. In addition, various mechanisms by which cannabis may act as an alcohol substitute or complement are explored in depth with the goal of better understanding equivocal findings.

SEARCH METHODS

This review includes articles that were identified from a search for studies on alcohol and cannabis co-use, with a specific focus on studies exploring complementary versus substitution aspects of co-use. Search terms were included in Google Scholar, PsycINFO, MEDLINE, and Web of Science. Eligible studies were those that measured alcohol and cannabis co-use in human samples in laboratory, survey, or ecological momentary assessment studies, or that directly referenced substitution or complementary patterns of use.

SEARCH RESULTS

Search results returned 650 articles, with 95 meeting inclusion criteria.

DISCUSSION AND CONCLUSIONS

Results of this review reveal compelling evidence for both substitution and complementary effects, suggesting nuanced yet significant distinctions across different populations examined in these studies. Several mechanisms for the impact of cannabis use on alcohol-related outcomes are identified, including patterns and context of co-use, timing and order of use, cannabinoid formulation, pharmacokinetic interactions, and user characteristics (including diagnostic status), all of which may influence substitution versus complementary effects. This review will inform future research studies examining this topic in both clinical and community samples and aid in the development of treatment and prevention efforts targeting those populations most vulnerable to negative consequences of co-use. Finally, this review highlights the need for additional research in more diverse samples and the use of mixed-methods designs to examine both pharmacological and contextual influences on co-use.

HCV Cure and Cannabis Abstinence Facilitate Tobacco Smoking Quit Attempts in HIV-HCV Co-Infected Patients (ANRS CO13 HEPAVIH Cohort Study)

In Western countries, tobacco smoking is highly prevalent among patients co-infected with HIV and hepatitis C virus (HCV). In the era of antiretrovirals and HCV cure, smoking-related health damages contribute greatly to morbidity and mortality in HIV-HCV co-infected patients. We used longitudinal data from the ANRS CO13 HEPAVIH cohort to identify the correlates of tobacco smoking quit attempts (TSQA) in HIV-HCV co-infected patients. TSQA were modelled using a multivariable discrete-time Cox proportional hazards model in 695 HIV-HCV co-infected tobacco smokers. HCV cure was associated with a 76% higher chance of TSQA (adjusted hazard ratio [95% confidence interval]: 1.76 [1.06-2.93], p = 0.029), and cannabis use with a 37% lower chance (0.63 [0.40-1.00], p = 0.049), independently of the mode of HIV transmission, other psychoactive substance use, and body mass index. Patients should be screened for tobacco and cannabis use at HCV treatment initiation and during follow-up. They should also be provided with comprehensive counselling and referral to addiction services. Non-smoking routes of cannabis administration should be promoted for cannabis users who wish to quit smoking tobacco.

A systematic review of addiction substitution in recovery: Clinical lore or empirically-based?

This systematic review synthesized the literature examining addiction substitution during recovery from substance use or behavioral addictions. A total of 96 studies were included with sample sizes ranging from 6 to 14,885. The most common recovery addictions were opioids (30.21%), followed by cannabis (20.83%), unspecified use (17.71%), nicotine (12.50%), alcohol (12.50%), cocaine (4.17%), and gambling (2.08%). Statistical results were provided by 70.83% of the studies. Of these, 17.65% found support for addiction substitution, whereas 52.94% found support for concurrent recovery. A total of 19.12% found no statistical changes and 10.29% found both significant increases and decreases. The remaining 29.17% of studies provided descriptive data, without statistical tests. Predictors of addiction substitution were provided by 22.92% of the studies and 11.46% included information on impact of addiction substitution on treatment outcomes. Overall, male gender, younger age, greater substance use severity, and presence of mental health disorders were associated with addiction substitution. Addiction substitution was associated with poorer treatment outcomes. A limitation of the present systematic review is the use of significance counting for the quantitative synthesis. More research examining changes in addiction during recovery would aid in the development of more effective treatments for addictive disorders and prevent addiction substitution.

Self-reported reductions in tobacco and nicotine use following medical cannabis initiation: Results from a cross-sectional survey of authorized medical cannabis patients in Canada

BACKGROUND

Despite decades of campaigns aimed at reducing tobacco/nicotine (T/N) use and the development of many different T/N reduction and cessation strategies, the impacts on international public health remain significant. Some studies have found an association between medical and non-medical cannabis use and T/N use, although the evidence on whether cannabis/cannabinoids increase or decrease the odds of reducing or ceasing T/N use remain contradictory. This paper explores the self-reported use of cannabis and associated changes in T/N use among a Canadian medical cannabis patient population.

METHODS

This study examines the impact of medical cannabis on T/N use by comparing self-reported patterns of use before and after the initiation of medical cannabis. Participants completed an online cross-sectional survey examining demographics, patterns of medical cannabis use, and the impact of medical cannabis on the use of T/N and other substances. The survey also included novel measures examining whether patients intended to use medical cannabis to reduce T/N use or had experience with other pharmacological or psychobehavioral T/N cessation strategies. We conducted a series of descriptive analyses and univariate and multivariate logistic regressions to explore the potential association between primary variables of interest and T/N reduction and cessation.

RESULTS

In total, the study recruited 2102 individuals, of whom 650 were current or former T/N users. Following initiation of medical cannabis use 320 (49%) T/N users self-reported reductions in use, with 160 (24.6%) reporting no T/N use in the 30 days prior to the survey. Odds of T/N cessation were greater among those who were age 55 or older (Adjusted Odds Ratio [AOR] = 2.56, 95% Confidence Interval [CI] 1.53-4.26), or those who reported >25 T/N uses per day in the pre-period (AOR = 2.11, 95% CI 1.14-3.92). Specific intent to use medical cannabis to quit resulted in significantly greater odds of reducing T/N use (AOR = 2.79, 95% CI 1.49-5.22); however, involvement with traditional T/N cessation treatments (pharmacological or psychobehavioral) was negatively associated with T/N cessation (AOR 0.39, 95% CI 0.18-0.86).

CONCLUSIONS

Results from this retrospective survey of medical cannabis users suggest that initiation of medical cannabis use was associated with self-reported reductions and/or cessation of T/N use in nearly half of study participants. In light of the significant morbidity, mortality, and health care costs related to T/N dependence, future research should further evaluate the potential of cannabis-based treatments to support efforts to reduce or cease T/N use.

Effects of a cannabis use disorder text message-delivered treatment on young adult alcohol misuse: Differential effects by gender

Alcohol misuse is more prevalent, frequent, and severe among young adults who use cannabis. Treatment of dual alcohol and cannabis users may have mixed results, with some studies reporting that alcohol misuse increases when cannabis use decreases (substance substitution), while others report that alcohol misuse decreases along with decreasing cannabis use (treatment spillover), and others report no association. Additionally, little research tests whether gender differences are found in treatment of dual alcohol and cannabis users, which may be expected given previous alcohol-focused treatments showing larger effects for females. In the current study, we present a secondary analysis of a randomized clinical trial testing a text message-delivered cannabis use disorder (CUD) treatment (peer network counseling text or "PNC-txt"). The trial included 101 young adults ages 18-25 who met criteria for CUD. We tested whether alcohol use and binge drinking frequency (4+/5+ drinks for women/men) decreased in response to the PNC-txt treatment, which has previously shown effectiveness in reducing cannabis use days. Latent growth models tested PNC-txt effects on the monthly rate of change in alcohol use and binge drinking across three months. In the full sample, we found no evidence of significant treatment effects on alcohol use (d = -0.07) or binge drinking (d = -0.10). Moderation analyses, however, indicated the PNC-txt effect on both alcohol use and binge drinking differed significantly by gender. PNC-txt led to significantly larger decreases in alcohol use (d = -0.53) and binge drinking days (d = -0.43) across the three months for females, whereas the study saw opposite (but nonsignificant) effects for males (d = 0.30 and 0.16 for alcohol use and binge drinking, respectively). We found no evidence that reductions in alcohol use and binge drinking were associated with cannabis use decreases, arguing against direct substitution or spillover effects. These results provide evidence that treatments focused on cannabis use may have secondary beneficial effects for young-adult alcohol misuse, although such effects may be limited to women.

Alcohol substitution during one month of cannabis abstinence among non-treatment seeking youth

OBJECTIVE

Cannabis and alcohol use are correlated behaviors among youth. It is not known whether discontinuation of cannabis use is associated with changes in alcohol use. This study assessed alcohol use in youth before, during, and after 4 weeks of paid cannabis abstinence.

METHODS

Healthy, non-treatment seeking, cannabis users (n = 160), aged 14-25 years, 84% of whom used alcohol in the last month, were enrolled for a 4-week study with a 2-4 week follow-up. Participants were randomly assigned to 4 weeks of either biochemically-verified cannabis abstinence achieved through a contingency management framework (CB-Abst) or monitoring with no abstinence requirement (CB-Mon). Participants were assessed at baseline and approximately 4, 6, 10, 17, 24, and 31 days after enrollment. A follow-up visit with no cannabis abstinence requirement for CB-Abst was conducted after 2-4 weeks.

RESULTS

Sixty percent of individuals assigned to the CB-Abst condition increased in frequency and quantity of alcohol consumption during the 4-week period of incentivized cannabis abstinence. As a whole, CB-Abst increased by a mean of 0.6 drinking days and 0.2 drinks per day in the initial week of abstinence (p's < 0.006). There was no evidence for further increases in drinking frequency or quantity during the 30-day abstinence period (p's > 0.53). There was no change in drinking frequency or quantity during the 4-week monitoring or follow-up periods among CB-Mon.

CONCLUSIONS

On average, 4 weeks of incentivized (i.e., paid) cannabis abstinence among non-treatment seeking youth was associated with increased frequency and amount of alcohol use in week 1 that was sustained over 4 weeks and resolved with resumption of cannabis use. However, there was notable variability in individual-level response, with 60% increasing in alcohol use and 23% actually decreasing in alcohol use during cannabis abstinence. Findings suggest that increased alcohol use during cannabis abstinence among youth merits further study to determine whether this behavior occurs among treatment seeking youth and its clinical significance.

Effects of vapourized THC and voluntary alcohol drinking during adolescence on cognition, reward, and anxiety-like behaviours in rats

Cannabis and alcohol co-use is prevalent in adolescence, but the long-term behavioural effects of this co-use remain largely unexplored. The aim of this study is to investigate the effects of adolescent alcohol and Δ⁹-tetrahydracannabinol (THC) vapour co-exposure on cognitive- and reward-related behaviours. Male Sprague-Dawley rats received vapourized THC (10 mg vapourized THC/four adolescent rats) or vehicle every other day (from post-natal day (PND) 28-42) and had continuous voluntary access to ethanol (10% volume/volume) in adolescence. Alcohol intake was measured during the exposure period to assess the acute effects of THC on alcohol consumption. In adulthood (PND 56+), rats underwent behavioural testing. Adolescent rats showed higher alcohol preference, assessed using the two-bottle choice test, on days on which they were not exposed to THC vapour. In adulthood, rats that drank alcohol as adolescents exhibited short-term memory deficits and showed decreased alcohol preference; on the other hand, rats exposed to THC vapour showed learning impairments in the delay-discounting task. Vapourized THC, alcohol or their combination had no effect on anxiety-like behaviours in adulthood. Our results show that although adolescent THC exposure acutely affects alcohol drinking, adolescent alcohol and cannabis co-use may not produce long-term additive effects.

Substitute Addictions in Persons with Substance Use Disorders: A Scoping Review

Substitute addictions, addictive behaviors that sequentially replace each other's functions, have implications for recovery trajectories but remain poorly understood. We sought to scope the extent, range, and characteristics of research on substitute addictions in persons with substance use disorders. Method: Using Arksey and O'Malley's framework for scoping reviews, a systematic search was conducted to identify publications that referenced substitute addictions up to April 2018. Study characteristics were extracted and summarized to provide an overview of the extant literature. Results: The 63 included studies show that substitute addictions are terminologically and conceptually ambiguous. Much of the available literature is concentrated in developed contexts - and in particular the United States of America. While presentations varied, at least two sub-types of substitute addictions appeared: long-term replacement and temporary replacement. Existing theories suggest a multifactorial etiology. Conclusions: The findings suggest a strong need for: increased awareness of substitute addictions and its potential consequences for recovery; interventions that structure prevention and pre-, during-, and post-treatment interactions as well as future research to explore its nature and dynamics drawing on multiple methods.

Treatment Implications Associated with Cannabis and Tobacco Co-Use

PURPOSE OF THE REVIEW

The goal of this article is to summarize the treatment-focused literature on cannabis and tobacco co-use and the treatment implications of co-use. This review will focus on: 1) the impact of co-use on cessation outcomes, 2) compensatory use/substitution of the non-treated substance among co-users, and 3) treatment interventions to address co-use. This article will highlight the limitations to co-use captured in the literature and offer considerations and directives for co-use research and treatment moving forward.

RECENT FINDINGS

The degree to which co-use affects cessation for a single, targeted substance remains in question, as the literature is largely mixed. Cannabis treatment trials are better equipped to answer these questions given that they do not typically exclude tobacco users. While the relationship between tobacco use and poorer cannabis outcomes appears to have some evidence, the reverse relationship (cannabis use affecting tobacco outcomes) is not consistently supported.

SUMMARY

The co-use of cannabis and tobacco and its impact on single substance cessation and/or compensatory substance use during cessation is generally overlooked in treatment trials, while interventions to address both substances are rare. Capturing co-use adds burden for researchers, clinicians, and participants, but is warranted given the prevalence of co-use and a rapidly changing cannabis and tobacco regulatory environment, which may further complicate co-occurring substance use. Co-users are a heterogeneous population; trials focused on co-users, in addition to better data capture and consistent terminology, will aid in an understanding of nuanced patterns of co-use critical to inform treatment interventions.

Reductions in alcohol use following medical cannabis initiation: results from a large cross-sectional survey of medical cannabis patients in Canada

BACKGROUND

Evidence details how cannabis can influence the use of other psychoactive substances, including prescription medications, alcohol, tobacco and illicit drugs, but very little research has examined the factors associated with these changes in substance use patterns. This paper explores the self-reported use of cannabis as a substitute for alcohol among a Canadian medical cannabis patient population.

METHODS

Data was derived from a survey of 2102 people enrolled in the Canadian medical cannabis program. We included 973 (44%) respondents who reported using alcohol on at least 10 occasions over a 12 month period prior to initiating medical cannabis, and then used retrospective data on the frequency and amount of alcohol use pre-and post medical cannabis initiation to determine which participant characteristics and other variables were associated with reductions and/or cessation of alcohol use.

RESULTS

Overall, 419 (44%) participants reported decreases in alcohol usage frequency over 30 days, 323 (34%) decreased the number of standard drinks they had per week, and 76 (8%) reported no alcohol use at all in the 30 days prior to the survey. Being below 55 years of age and reporting higher rates of alcohol use in the pre-period were both associated with greater odds of reducing alcohol use, and an intention to use medical cannabis to reduce alcohol consumption was associated with significantly greater odds of both reducing and ceasing alcohol use altogether.

CONCLUSIONS

Our findings suggest that medical cannabis initiation may be associated with self-reported reductions and cessation of alcohol use among medical cannabis patients. Since alcohol is the most prevalent recreational substance in North America, and its use results in significant rates of criminality, morbidity and mortality, these findings may result in improved health outcomes for medical cannabis patients, as well as overall improvements in public health and safety.

Does cannabis complement or substitute alcohol consumption? A systematic review of human and animal studies

BACKGROUND

Whether alcohol and cannabis complement or substitute each other has been studied for over two decades. In the changing cannabis policy landscape, debates are moving rapidly and spill-over effects on other substances are of interest.

AIMS

update and extend a previous systematic review, by: (a) identifying new human behavioural studies reporting on substitution and/or complementarity of alcohol and cannabis, and (b) additionally including animal studies.

METHODS

We replicated the search strategy of an earlier systematic review, supplemented with a new search for animal studies. Search results were crossed checked against the earlier review and reference lists were hand searched. Findings were synthesised using a narrative synthesis.

RESULTS

Sixty-five articles were included (64 in humans, one in animals). We synthesised findings into categories: patterns of use, substitution practices, economic relationship, substance use disorders, policy evaluation, others and animal studies. Overall, 30 studies found evidence for substitution, 17 for complementarity, 14 did not find evidence for either, and four found evidence for both.

CONCLUSIONS

Overall, the evidence regarding complementarity and substitution of cannabis and alcohol is mixed. We identified stronger support for substitution than complementarity, though evidence indicates different effects in different populations and to some extent across different study designs. The quality of studies varied and few were designed specifically to address this question. Dedicated high-quality research is warranted.

Decreased drinking in adults with co-occurring cannabis and alcohol use disorders in a treatment trial for marijuana dependence: Evidence of a secondary benefit?

The purpose of the present study was to investigate whether cannabis dependent users who met criteria for a secondary diagnosis of alcohol use disorder (AUD) would increase their use of alcohol in response to decreasing their use of marijuana in a behavioral treatment trial for cannabis use disorder (CUD). This phenomenon is commonly known as "substance substitution." Participants were randomly assigned to one of four 9-session treatment conditions with cannabis and alcohol use measured at baseline, posttreatment, and at 4 follow-ups through 14 months. Of those enrolled (n = 198), 27 (13.6%) also met criteria for AUD. Linear mixed models were used to analyze alcohol use over time with cannabis use and time as predictors. Findings demonstrated that there were no associations between declines in cannabis use and changes in alcohol consumption in the full sample. However, among those with CUD who also had AUD, declines in cannabis use significantly predicted concurrent declines in alcohol use (p < .05). This study did not find evidence of substance substitution among individuals receiving treatment for CUD. Contrary to expectations, the results indicated that individuals with AUD were more likely to decrease, rather than increase, their alcohol use when they reduced their marijuana use. Treatment for CUD in this study appeared to result in improvements in substance use generally, at least for those with comorbid AUD.

Alcohol, tobacco, and marijuana consumption is associated with increased odds of same-day substance co- and tri-use

BACKGROUND

Little is known about event-level patterns of marijuana co- or tri-use with alcohol and tobacco. Thus, the study goal was to examine patterns of same-day alcohol, cigarette, and marijuana co- and tri-use at the individual level in non-treatment-seeking alcohol users.

METHODS

Participants (N = 551) completed an in-person interview for alcohol, cigarette, and marijuana use over the previous 30 days, and the event-level substance use patterns of n = 179 participants who reported using each of these substances at least once per month were analyzed.

RESULTS

The use of alcohol, marijuana, or cigarettes independently increased the probability of subsequent, simultaneous co-use of one of the two remaining substances. The co-use of alcohol with cigarettes and marijuana with cigarettes produced generally additive effects on the odds of same day tri-use of marijuana and alcohol, respectively. Conversely, the co-use of alcohol and marijuana produced sub-additive effects on likelihood of cigarette use. Sex moderated several of the observed patterns of co- and tri-use: the relationship between alcohol or cigarette use predicting marijuana co-use was stronger in men, whereas the observed additive relationships between drug co-use leading to tri-use was stronger in women.

CONCLUSIONS

The presented results may aid in the understanding of how simultaneous co-use of marijuana with alcohol and/or tobacco relates to the etiology, maintenance, and treatment of comorbid and trimorbid substance use disorder. Replication and extension of the results in treatment seeking populations using more fine-grained analysis approaches, e.g. ecological momentary assessment, is needed.

Tobacco use during cannabis cessation: Use patterns and impact on abstinence in a National Drug Abuse Treatment Clinical Trials Network study

BACKGROUND

It is common for cannabis users to also use tobacco. While data suggest that tobacco users have more difficulty achieving cannabis cessation, secondary analyses of clinical trial data sets may provide insight into the moderating variables contributing to this relationship, as well as changes in tobacco use during cannabis treatment. Those were the aims of this secondary analysis.

METHODS

The parent study was a multi-site trial of N-acetylcysteine for cannabis dependence conducted within the National Drug Abuse Treatment Clinical Trials Network. Participants were treatment-seeking adults (ages 18-50) who met criteria for cannabis dependence (N = 302). For cigarette smokers (n = 117), tobacco use was assessed via timeline follow-back and nicotine dependence was assessed via the Fagerström Test for Nicotine Dependence (FTND). Outcome measures included: 1) changes in tobacco use based on treatment assignment, nicotine dependence, and concurrent cannabis reduction/abstinence, and 2) independent associations between nicotine dependence and cannabis abstinence.

RESULTS

Cigarette smokers accounted for 39% of the sample (117/302), with a median FTND score of 3.0 (10-point scale). Among those with lower baseline nicotine dependence scores, cigarette smoking was reduced in the active treatment group compared to placebo. Those with moderate/high levels of nicotine dependence showed slight increases in smoking following active treatment. Nicotine dependence did not affect cannabis cessation.

CONCLUSIONS

Cigarette smoking during cannabis treatment was affected, but depended on baseline nicotine dependence severity, though dependence levels did not impact cannabis abstinence. Interventions that address both tobacco and cannabis are needed, especially due to an increasing prevalence of cannabis use.

Mobile contingency management as an adjunctive treatment for co-morbid cannabis use disorder and cigarette smoking

INTRODUCTION

Cannabis is the most widely used illicit drug in the U.S. with 19.8 million current users. Population-based data indicate that almost all cannabis users (90%) have a lifetime history of tobacco smoking and the majority (74%) currently smoke tobacco. Among cannabis users, smoking tobacco is associated with increased frequency of cannabis use, increased morbidity, and poorer cannabis cessation outcomes. There is a lack of research, however, focused on addressing cessation of both substances simultaneously. The purpose of the current pilot study was to evaluate the feasibility and acceptability of a multi-component tobacco/cannabis abstinence treatment.

METHODS

Five participants completed Abstinence Reinforcement Therapy, an intervention that included five sessions of cognitive-behavioral telephone counseling for tobacco/cannabis, pharmacotherapy for smoking cessation, and five weeks of mobile contingency management to remain abstinent from tobacco and cannabis.

RESULTS

Feasibility of recruitment, retention and treatment completion was high. Satisfaction with the treatment was also high.

CONCLUSION

Results support the feasibility and acceptability of this approach with dual cannabis and tobacco users and suggest that further research examining the efficacy of this approach is warranted.

Changes in tobacco consumption in cannabis dependent patients with schizophrenia versus non-psychiatric controls during 28-days of cannabis abstinence

BACKGROUND

Tobacco and cannabis are highly co-morbid in the general population and in patients with schizophrenia. Given the putative causal mechanisms facilitating co-use, it is important to determine how cannabis cessation may influence concurrent tobacco use. Using a 28-day cannabis abstinence paradigm, we prospectively examined changes in tobacco consumption in patients with schizophrenia and controls with cannabis dependence and daily cigarette use.

METHODS

Cannabis dependent patients with schizophrenia (n = 19) and controls (n = 20) completed the study with abstinence rates of 42% and 55%, respectively. Participants completed measures of substance use, withdrawal, and clinical symptoms weekly. Urine samples were collected twice weekly to biochemically verify abstinence.

RESULTS

Patients reported a greater increase in cigarettes smoked per day (CPD) on Day 7 relative to baseline (2.97 cigarette increase for abstinent subgroup, p < .01) compared to controls (.06 cigarette increase for abstinent subgroup, p = .95). Initially, greater reductions in cannabis use related to greater increases in CPD relative to baseline in the patient subsample (simple slope = -2.31, p = .05), but by Day 28, CPD returned to baseline levels independent of cannabis use. CPD changes were unrelated to cannabis withdrawal. Results were similar for changes in caffeine consumption, but not for alcohol.

CONCLUSIONS

Findings suggest transient tobacco substitution for cannabis in patients with schizophrenia. This provides further support for a strong association between cannabis and tobacco in schizophrenia. Future studies should focus on targeting underlying mechanisms that promote co-use to better address potential changes in concurrent substance use during treatment interventions.

The cannabis withdrawal syndrome: current insights

The cannabis withdrawal syndrome (CWS) is a criterion of cannabis use disorders (CUDs) (Diagnostic and Statistical Manual of Mental Disorders - Fifth Edition) and cannabis dependence (International Classification of Diseases [ICD]-10). Several lines of evidence from animal and human studies indicate that cessation from long-term and regular cannabis use precipitates a specific withdrawal syndrome with mainly mood and behavioral symptoms of light to moderate intensity, which can usually be treated in an outpatient setting. Regular cannabis intake is related to a desensitization and downregulation of human brain cannabinoid 1 (CB1) receptors. This starts to reverse within the first 2 days of abstinence and the receptors return to normal functioning within 4 weeks of abstinence, which could constitute a neurobiological time frame for the duration of CWS, not taking into account cellular and synaptic long-term neuroplasticity elicited by long-term cannabis use before cessation, for example, being possibly responsible for cannabis craving. The CWS severity is dependent on the amount of cannabis used pre-cessation, gender, and heritable and several environmental factors. Therefore, naturalistic severity of CWS highly varies. Women reported a stronger CWS than men including physical symptoms, such as nausea and stomach pain. Comorbidity with mental or somatic disorders, severe CUD, and low social functioning may require an inpatient treatment (preferably qualified detox) and post-acute rehabilitation. There are promising results with gabapentin and delta-9-tetrahydrocannabinol analogs in the treatment of CWS. Mirtazapine can be beneficial to treat CWS insomnia. According to small studies, venlafaxine can worsen the CWS, whereas other antidepressants, atomoxetine, lithium, buspirone, and divalproex had no relevant effect. Certainly, further research is required with respect to the impact of the CWS treatment setting on long-term CUD prognosis and with respect to psychopharmacological or behavioral approaches, such as aerobic exercise therapy or psychoeducation, in the treatment of CWS. The up-to-date ICD-11 Beta Draft is recommended to be expanded by physical CWS symptoms, the specification of CWS intensity and duration as well as gender effects.

Medical cannabis access, use, and substitution for prescription opioids and other substances: A survey of authorized medical cannabis patients

BACKGROUND

In 2014 Health Canada replaced the Marihuana for Medical Access Regulations (MMAR) with the Marihuana for Medical Purposes Regulations (MMPR). One of the primary changes in the new program has been to move from a single Licensed Producer (LP) of cannabis to multiple Licensed Producers. This is the first comprehensive survey of patients enrolled in the MMPR.

METHODS

Patients registered to purchase cannabis from Tilray, a federally authorized Licenced Producer (LP) within the MMPR, were invited to complete an online survey consisting of 107 questions on demographics, patterns of use, and cannabis substitution effect. The survey was completed by 271 respondents.

RESULTS

Cannabis is perceived to be an effective treatment for diverse conditions, with pain and mental health the most prominent. Findings include high self-reported use of cannabis as a substitute for prescription drugs (63%), particularly pharmaceutical opioids (30%), benzodiazepines (16%), and antidepressants (12%). Patients also reported substituting cannabis for alcohol (25%), cigarettes/tobacco (12%), and illicit drugs (3%). A significant percentage of patients (42%) reported accessing cannabis from illegal/unregulated sources in addition to access via LPs, and over half (55%) were charged to receive a medical recommendation to use cannabis, with nearly 25% paying $300 or more.

CONCLUSION

The finding that patients report its use as a substitute for prescription drugs supports prior research on medical cannabis users; however, this study is the first to specify the classes of prescription drugs for which cannabis it is used as a substitute, and to match this substitution to specific diagnostic categories. The findings that some authorized patients purchase cannabis from unregulated sources and that a significant percentage of patients were charged for medical cannabis recommendations highlight ongoing policy challenges for this federal program.

Evaluation of a reduced nicotine product standard: Moderating effects of and impact on cannabis use

INTRODUCTION

The Family Smoking Prevention and Tobacco Control Act authorized the FDA to reduce the nicotine content in cigarettes. Research is needed to guide proposed regulations, including evaluation of consequences to public health. This study evaluated how a reduced nicotine product standard might be moderated by and impact cannabis use.

METHODS

Secondary analysis of a controlled clinical trial examining the effects of nicotine content in cigarettes in adult daily smokers. Linear regression assessed whether baseline cannabis use moderated behavioral, subjective, or physiological effects of smoking very low nicotine content (VLNC) versus normal nicotine content (NNC) cigarettes. Repeated measures analysis of associations between nicotine condition and prevalence and frequency of cannabis use was completed using generalized estimating equations (GEE).

RESULTS

Cannabis use did not moderate most of the following effects of VLNC cigarettes: Among cannabis users and non-users, smokers randomized to VLNC cigarettes reported lower nicotine dependence, cigarettes per day, biomarkers of nicotine exposure, and craving compared to smokers randomized to NNC cigarettes. Non-cannabis using smokers randomized to VLNC cigarettes also reported lower smoking dependence motives and had lower tobacco-specific nitrosamine exposure and total puff volume versus smokers randomized to NNC cigarettes. For cannabis users, smokers randomized to VLNC cigarettes reported decreased positive affect. VLNC cigarette use did not impact the prevalence or frequency of cannabis use.

DISCUSSION

Findings provide evidence that nicotine reduction in cigarettes could have beneficial effects on cigarette smoking regardless of cannabis use. Results suggest that transitioning to VLNC cigarettes is unlikely to alter current rates of cannabis use.

Substitution and Complementarity of Alcohol and Cannabis: A Review of the Literature

BACKGROUND

Whether alcohol and cannabis are used as substitutes or complements remains debated, and findings across various disciplines have not been synthesized to date.

OBJECTIVE

This article is a first step towards organizing the interdisciplinary literature on alcohol and cannabis substitution and complementarity.

METHOD

Electronic searches were performed using PubMed and ISI Web of Knowledge. Behavioral studies of humans with "alcohol" (or "ethanol") and "cannabis" (or "marijuana") and "complement(*)" (or "substitut(*)") in the title or as a keyword were considered. Studies were organized according to sample characteristics (youth, general population, clinical and community-based). These groups were not set a priori, but were informed by the literature review process.

RESULTS

Of the 39 studies reviewed, 16 support substitution, ten support complementarity, 12 support neither and one supports both. Results from studies of youth suggest that youth may reduce alcohol in more liberal cannabis environments (substitute), but reduce cannabis in more stringent alcohol environments (complement). Results from the general population suggest that substitution of cannabis for alcohol may occur under more lenient cannabis policies, though cannabis-related laws may affect alcohol use differently across genders and racial groups.

CONCLUSIONS

Alcohol and cannabis act as both substitutes and complements. Policies aimed at one substance may inadvertently affect consumption of other substances. Future studies should collect fine-grained longitudinal, prospective data from the general population and subgroups of interest, especially in locations likely to legalize cannabis.

Attempts to stop or reduce daily cannabis use: An intensive natural history study

We attempted to replicate and add to our prior study of attempts to stop or reduce cannabis use among daily cannabis users trying to change on their own, by observing a larger sample and adding further clinically relevant outcomes. Daily users (n = 193) who intended to stop or reduce sometime in the next 3 months called an Interactive Voice Response system each morning for 3 months to report on cannabis use, attempts to stop or reduce, withdrawal symptoms, and so forth, on the prior day. This study replicated our prior findings that (a) cannabis users trying to change make many, and often rapid, transitions among use as usual, reduction, and abstinence; (b) reduction attempts are more common than abstinence attempts; (c) quit and reduction attempts are short-lived and few participants achieve long-term abstinence; (d) alcohol and drug use are not greater on abstinence days; and (e) few users seek treatment. Novel findings included (f) a greater number of days of abstinence or intentional reduction predicted a greater decline in cannabis dependence, (g) most users do not prepare before their quit attempt, (h) coping outcomes during abstinence predict increased duration of abstinence, (i) tobacco use is less common on days of abstinence, and (j) withdrawal symptoms occur even with short quit attempts. Replication tests in more generalizable samples and of longer duration are indicated. Further natural history studies are likely to provide information to help improve the content of psychological treatments for cannabis use. (PsycINFO Database Record

Substituting cannabis for prescription drugs, alcohol and other substances among medical cannabis patients: The impact of contextual factors

INTRODUCTION AND AIMS

Recent years have witnessed increased attention to how cannabis use impacts the use of other psychoactive substances. The present study examines the use of cannabis as a substitute for alcohol, illicit substances and prescription drugs among 473 adults who use cannabis for therapeutic purposes.

DESIGN AND METHODS

The Cannabis Access for Medical Purposes Survey is a 414-question cross-sectional survey that was available to Canadian medical cannabis patients online and by hard copy in 2011 and 2012 to gather information on patient demographics, medical conditions and symptoms, patterns of medical cannabis use, cannabis substitution and barriers to access to medical cannabis.

RESULTS

Substituting cannabis for one or more of alcohol, illicit drugs or prescription drugs was reported by 87% (n = 410) of respondents, with 80.3% reporting substitution for prescription drugs, 51.7% for alcohol, and 32.6% for illicit substances. Respondents who reported substituting cannabis for prescription drugs were more likely to report difficulty affording sufficient quantities of cannabis, and patients under 40 years of age were more likely to substitute cannabis for all three classes of substance than older patients.

DISCUSSION AND CONCLUSIONS

The finding that cannabis was substituted for all three classes of substances suggests that the medical use of cannabis may play a harm reduction role in the context of use of these substances, and may have implications for abstinence-based substance use treatment approaches. Further research should seek to differentiate between biomedical substitution for prescription pharmaceuticals and psychoactive drug substitution, and to elucidate the mechanisms behind both. [Lucas P, Walsh Z, Crosby K, Callaway R, Belle-Isle L, Kay B, Capler R, Holtzman S. Substituting cannabis for prescription drugs, alcohol, and other substances among medical cannabis patients: The impact of contextual factors. Drug Alcohol Rev 2016;35:326-333].

Cannabinoid Ligands and Alcohol Addiction: A Promising Therapeutic Tool or a Humbug?

The vast therapeutic potential of cannabinoids of both synthetic and plant-derived origins currently makes these compounds the focus of a growing interest. Although cannabinoids are still illicit drugs, their possible clinical usefulness, including treatment of acute or neuropathic pain, have been suggested by several studies. In addition, some observations indicate that cannabinoid receptor antagonists may be useful for the treatment of alcohol dependence and addiction, which is a major health concern worldwide. While the synergism between alcohol and cannabinoid agonists (in various forms) creates undesirable side effects when the two are consumed together, the administration of CB1 antagonists leads to a significant reduction in alcohol consumption. Furthermore, cannabinoid antagonists also mitigate alcohol withdrawal symptoms. Herein, we present an overview of studies focusing on the effects of cannabinoid ligands (agonists and antagonists) during acute or chronic consumption of ethanol.

Post-treatment drinking among HIV patients: Relationship to pre-treatment marijuana and cocaine use

BACKGROUND

For individuals with HIV, heavy drinking can pose serious threats to health. Some interventions are effective at reducing drinking in this population, but many HIV-infected heavy drinkers also use marijuana or cocaine. Although these drugs have predicted poor alcohol outcomes in other treatment studies, whether this occurs among HIV patients who drink heavily is unknown.

METHODS

Participants were binge-drinking HIV primary care patients (N=254) enrolled in a randomized trial of three brief drinking interventions over 60 days that varied in intensity. We investigated the relationship of baseline past-year drug use (marijuana-only, cocaine-only, both, neither) to end-of-treatment drinking quantity and frequency. We also evaluated whether the relationship between intervention type and end-of-treatment drinking varied by baseline drug use. Final models incorporated control for patients' demographic and HIV characteristics.

RESULTS

In final models, drinking frequency at the end of treatment did not vary by baseline drug use, but drinking quantity did (X(2)[3] = 13.87, p < 0.01), with individuals using cocaine-only drinking significantly more per occasion (B = 0.32, p < 0.01). Baseline drug use also interacted with intervention condition in predicting end-of-treatment drinking quantity (X(2)[6] = 13.98, p < 0.05), but not frequency, with the largest discrepancies in end-of-treatment drinks per drinking day by intervention intensity among cocaine-only patients.

CONCLUSIONS

In general, HIV patients using cocaine evidenced the highest levels of drinking after alcohol intervention. However, these individuals also evidenced the most pronounced differences in end-of-treatment drinking by intervention intensity. These results suggest the importance of more intensive intervention for individuals using alcohol and cocaine.

Differences in Tobacco Product Use Among Past Month Adult Marijuana Users and Nonusers: Findings From the 2003-2012 National Survey on Drug Use and Health

INTRODUCTION

This study assessed differences in individual tobacco product use between past month marijuana users and nonusers, and trends in overall tobacco use and use of specific tobacco products among marijuana users.

METHODS

Data were obtained from 378 459 adults participating in the 2003-2012 National Survey on Drug Use and Health, a cross-sectional, household interview survey conducted annually. Data from the most recent 2 years (2011-2012) were used to assess differences in the prevalence of various tobacco products by past month marijuana status. Data from all years were used to assess historical trends in overall tobacco use, and use of cigarettes, cigars, and blunts among marijuana users; trend significance was assessed using orthogonal polynomials.

RESULTS

From 2011-2012, the prevalence of any past month tobacco use among the 9727 past month marijuana users was 68.6% excluding blunts, and 78.3% including blunts (vs. 25.3% for nonusers, P < .0001); 77.3% of past month marijuana users reported past month combusted tobacco use (vs. 23.4% of non-MJ users, P < .0001). By product, 60.1% of past month marijuana users reported past month cigarette use, 42.0% reported past month blunt use, and 20.6% reported past month cigar use. Overall, adjusted trends in past month cigarette use decreased, while trends in past month blunt use increased; cigar use did not change.

DISCUSSION

Tobacco use is highly prevalent among adult marijuana users and represents an important potential comorbidity of marijuana use. In light of increasing policies legalizing marijuana, it is critical to monitor changes in overall and specific tobacco product use.

Cannabis and psychopathology: The meandering journey of the last decade

Since its inception cannabis has been observed to be associated with various psycho-pathology. In this paper, the authors have reviewed the advancement made in this area over the last decade. The association between cannabis and schizophrenia has been researched more intensively. The controversy regarding the reliability, clinical utility, and the existence of a cannabis withdrawal syndrome has also been settled. Recent studies also buttressed the possibility of acute and chronic effect of cannabis on various cognitive functions. There has been a plethora of research regarding the treatment for cannabis use disorders. But the new and most interesting area of research is concentrated on the endocannabinoid system and its contribution in various psychiatric disorders.

Associations between cigarette smoking and cannabis dependence: a longitudinal study of young cannabis users in the United Kingdom

AIMS

To determine the degree to which cigarette smoking predicts levels of cannabis dependence above and beyond cannabis use itself, concurrently and in an exploratory four-year follow-up, and to investigate whether cigarette smoking mediates the relationship between cannabis use and cannabis dependence.

METHODS

The study was cross sectional with an exploratory follow-up in the participants' own homes or via telephone interviews in the United Kingdom. Participants were 298 cannabis and tobacco users aged between 16 and 23; follow-up consisted of 65 cannabis and tobacco users. The primary outcome variable was cannabis dependence as measured by the Severity of Dependence Scale (SDS). Cannabis and tobacco smoking were assessed through a self-reported drug history.

RESULTS

Regression analyses at baseline showed cigarette smoking (frequency of cigarette smoking: B=0.029, 95% CI=0.01, 0.05; years of cigarette smoking: B=0.159, 95% CI=0.05, 0.27) accounted for 29% of the variance in cannabis dependence when controlling for frequency of cannabis use. At follow-up, only baseline cannabis dependence predicted follow-up cannabis dependence (B=0.274, 95% CI=0.05, 0.53). At baseline, cigarette smoking mediated the relationship between frequency of cannabis use and dependence (B=0.0168, 95% CI=0.008, 0.288) even when controlling for possible confounding variables (B=0.0153, 95% CI=0.007, 0.027).

CONCLUSIONS

Cigarette smoking is related to concurrent cannabis dependence independently of cannabis use frequency. Cigarette smoking also mediates the relationship between cannabis use and cannabis dependence suggesting tobacco is a partial driver of cannabis dependence in young people who use cannabis and tobacco.

Lithium carbonate in the management of cannabis withdrawal: a randomized placebo-controlled trial in an inpatient setting

RATIONALE

Preclinical studies suggest that lithium carbonate (lithium) can reduce precipitated cannabinoid withdrawal in rats by stimulating release of the neuropeptide oxytocin, while two open-label studies indicate lithium may ameliorate cannabis withdrawal symptoms in humans.

OBJECTIVES

This study was conducted to examine the efficacy and safety of lithium in the inpatient management of cannabis withdrawal and to determine whether lithium affects plasma oxytocin and the rate of elimination of plasma cannabinoids during abstinence.

METHODS

Treatment-seeking cannabis-dependent adults (n = 38) were admitted for 8 days to an inpatient withdrawal unit and randomized to either oral lithium (500 mg) or placebo given twice a day under double-blind randomized controlled trial (RCT) conditions. Primary outcomes included withdrawal severity [cannabis withdrawal scale (CWS)], rates of detoxification completion, and adverse events. Plasma cannabinoids, plasma oxytocin and serum lithium levels were measured repeatedly over admission. Follow-up research interviews were conducted at 14, 30, and 90 days postdischarge.

RESULTS

Lithium did not significantly affect total CWS scores relative to placebo, although it significantly reduced individual symptoms of "loss of appetite," "stomach aches," and "nightmares/strange dreams." No significant group differences were found in treatment retention or adverse events. Lithium did not increase plasma oxytocin levels nor influence the rate of elimination of cannabinoids. Both placebo- and lithium-treated participants showed reduced levels of cannabis use (verified by urinalysis) and improved health and psychosocial outcomes at 30- and 90-day follow-up relative to pretreatment baselines.

CONCLUSIONS

Despite the strong rationale for the present study, the efficacy of lithium over placebo in the management of cannabis withdrawal was not demonstrated.

Implications of marijuana legalization for adolescent substance use

Marijuana that is legally available for adults has multiple implications for adolescent substance use. One potential effect that legalization may have is an increase in adolescent use to due increased availability, greater social acceptance, and possibly lower prices. Legalization may also facilitate the introduction of new formulations of marijuana (edible, vaporized) and with potentially higher potencies. It is unknown what adolescent consumption patterns will be if marijuana is widely available and marketed in different forms, or what effects different patterns of adolescent use will have on cognition, the development of marijuana use disorders, school performance, and the development of psychotic illnesses. Also unclear is whether adolescent users will be experiencing higher levels of tetrahydrocannabinol (THC) compared with previous generations of users due to higher potencies. Although previous studies of the effects of adolescent marijuana use provide some guidance for current policy and public health recommendations, many new studies will be needed that answer questions in the context of use within a legal adult environment. Claims that marijuana has medicinal benefits create additional challenges for adolescent prevention efforts, as they contrast with messages of its harmfulness. Prevention and treatment approaches will need to address perceptions of the safety of marijuana, claims of its medicinal use, and consider family-wide effects as older siblings and parents may increasingly openly consume and advocate for marijuana use. Guidance for primary care physicians will be needed regarded screening and counseling. Widespread legalization and acceptance of marijuana implies that as law enforcement approaches for marijuana control decline, public health, medical, and scientific efforts to understand and reduce negative consequences of adolescent marijuana use need to be substantially increased to levels commensurate with those efforts for tobacco and alcohol.