Adverse Effects of Cannabis on Adolescent Brain Development: A Longitudinal Study

The Role of Cannabis and The Endocannabinoid System in Sleep Regulation and Cognition: A Review of Human and Animal Studies

OBJECTIVES

Both sleep and cognition are partially modulated by the endocannabinoid (ECB) system. Cannabis has been reported to have effects on sleep and cognition. This review aims to summarize the recent literature on the ECB system, the role of cannabis and the ECB system on sleep regulation and cognition. Further, this review will identify existing gaps in knowledge and suggest potential targets for future research.

METHODS

We performed this review in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Reports were identified by searching PubMed/MEDLINE, Embase, CINAHL, Web of Science, and PsycINFO for articles published through September 2021 for studies with data available on aspects of cognition, cannabis, or the ECB system, and sleep or circadian rhythms (CRs).

RESULTS

We identified 6 human and 6 animal studies to be eligible for inclusion in this review. Several human studies found that cannabis use is not associated with changes in sleep quality or cognitive function. However, individual cannabinoids appeared to have independent effects on cognition and sleep; THC alone decreased cognitive performance and increased daytime sleepiness, whereas CBD alone had no effect on sleep or cognition. Animal studies demonstrated that manipulation of the ECB system altered activity and cognitive function, some of which appeared to be dependent on the light/dark cycle.

CONCLUSION

The sleep-wake cycle and CRs are both likely modulated by the ECB system, potentially resulting in effects on cognition, however this area is critically understudied.

The thalamus in psychosis spectrum disorder

Psychosis spectrum disorder (PSD) affects 1% of the world population and results in a lifetime of chronic disability, causing devastating personal and economic consequences. Developing new treatments for PSD remains a challenge, particularly those that target its core cognitive deficits. A key barrier to progress is the tenuous link between the basic neurobiological understanding of PSD and its clinical phenomenology. In this perspective, we focus on a key opportunity that combines innovations in non-invasive human neuroimaging with basic insights into thalamic regulation of functional cortical connectivity. The thalamus is an evolutionary conserved region that forms forebrain-wide functional loops critical for the transmission of external inputs as well as the construction and update of internal models. We discuss our perspective across four lines of evidence: First, we articulate how PSD symptomatology may arise from a faulty network organization at the macroscopic circuit level with the thalamus playing a central coordinating role. Second, we discuss how recent animal work has mechanistically clarified the properties of thalamic circuits relevant to regulating cortical dynamics and cognitive function more generally. Third, we present human neuroimaging evidence in support of thalamic alterations in PSD, and propose that a similar "thalamocortical dysconnectivity" seen in pharmacological imaging (under ketamine, LSD and THC) in healthy individuals may link this circuit phenotype to the common set of symptoms in idiopathic and drug-induced psychosis. Lastly, we synthesize animal and human work, and lay out a translational path for biomarker and therapeutic development.

A Meta-Analysis of fMRI Studies of Youth Cannabis Use: Alterations in Executive Control, Social Cognition/Emotion Processing, and Reward Processing in Cannabis Using Youth

Background: Adolescent cannabis use (CU) is associated with adverse health outcomes and may be increasing in response to changing cannabis laws. Recent imaging studies have identified differences in brain activity between adult CU and controls that are more prominent in early onset users. Whether these differences are present in adolescent CU and relate to age/developmental stage, sex, or cannabis exposure is unknown. Methods: A systematic review and subsequent effect-size seed-based d mapping (SDM) meta-analysis were conducted to examine differences in blood-oxygen-level-dependent (BOLD) response during fMRI studies between CU and non-using typically developing (TD) youth. Supplemental analyses investigated differences in BOLD signal in CU and TD youth as a function of sex, psychiatric comorbidity, and the dose and severity of cannabis exposure. Results: From 1371 citations, 45 fMRI studies were identified for inclusion in the SDM meta-analysis. These studies compared BOLD response contrasts in 1216 CU and 1486 non-using TD participants. In primary meta-analyses stratified by cognitive paradigms, CU (compared to TD) youth showed greater activation in the rostral medial prefrontal cortex (rmPFC) and decreased activation in the dorsal mPFC (dmPFC) and dorsal anterior cingulate cortex (dACC) during executive control and social cognition/emotion processing, respectively. In meta-regression analyses and subgroup meta-analyses, sex, cannabis use disorder (CUD) severity, and psychiatric comorbidity were correlated with brain activation differences between CU and TD youth in mPFC and insular cortical regions. Activation differences in the caudate, thalamus, insula, dmPFC/dACC, and precentral and postcentral gyri varied as a function of the length of abstinence. Conclusions: Using an SDM meta-analytic approach, this report identified differences in neuronal response between CU and TD youth during executive control, emotion processing, and reward processing in cortical and subcortical brain regions that varied as a function of sex, CUD severity, psychiatric comorbidity, and length of abstinence. Whether aberrant brain function in CU youth is attributable to common predispositional factors, cannabis-induced neuroadaptive changes, or both warrants further investigation.

The association between public health engagement in school-based substance use prevention programs and student alcohol, cannabis, e-cigarette and cigarette use

OBJECTIVE

This study examined the associations between public health engagement (PHE) in school-based substance use prevention programs and student substance use. For the purposes of this study, PHE refers to any form of collaboration between the local government public health agency and the school to promote the physical and mental health of students.

METHODS

Data for this study were collected from the Cannabis, Obesity, Mental health, Physical activity, Alcohol use, Smoking and Sedentary behaviour (COMPASS) study during the 2018/2019 data collection year. Multilevel logistic regression was used to analyze the associations between PHE and student substance use.

RESULTS

Data from 84 schools and 42,149 students were included; 70% of schools had PHE in substance use prevention programs. PHE in substance use prevention appears to have had no significant impact on student substance use in our models. When PHE was divided into five methods of engagement, it was found that when public health solved problems jointly with schools, the odds of a student using alcohol or cannabis significantly increased. When schools were split into low- and high-use schools for each substance measured, some methods of PHE significantly decreased the odds of cannabis and cigarette use in high-use schools and significantly increased the odds of alcohol and cannabis use in low-use schools.

CONCLUSION

This study highlights the need to develop better partnerships and collaborations between public health and schools, and the importance of ensuring that school-based substance use prevention programs are evidence-based and tailored to the specific needs of schools and students.

Is resting-state functional connectivity altered in regular cannabis users? A systematic review of the literature

RATIONALE

Regular cannabis use has been associated with brain functional alterations within frontal, temporal, and striatal pathways assessed during various cognitive tasks. Whether such alterations are consistently reported in the absence of overt task performance needs to be elucidated to uncover the core neurobiological mechanisms of regular cannabis use.

OBJECTIVES

We aim to systematically review findings from studies that examine spontaneous fluctuations of brain function using functional Magnetic Resonance Imaging (fMRI) resting-state functional connectivity (rsFC) in cannabis users versus controls, and the association between rsFC and cannabis use chronicity, mental health symptoms, and cognitive performance.

METHODS

We conducted a PROSPERO registered systematic review following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and searched eight databases.

RESULTS

Twenty-one studies were included for review. Samples comprised 1396 participants aged 16 to 42 years, of which 737 were cannabis users and 659 were controls. Most studies found greater positive rsFC in cannabis users compared to controls between frontal-frontal, fronto-striatal, and fronto-temporal region pairings. The same region pairings were found to be preliminarily associated with varying measures of cannabis exposure.

CONCLUSIONS

The evidence to date shows that regular cannabis exposure is consistently associated with alteration of spontaneous changes in Blood Oxygenation Level-Dependent signal without any explicit cognitive input or output. These findings have implications for interpreting results from task-based fMRI studies of cannabis users, which may additionally tax overlapping networks. Future longitudinal rsFC fMRI studies are required to determine the clinical relevance of the findings and their link to the chronicity of use, mental health, and cognitive performance.

Systematic review of structural and functional neuroimaging studies of cannabis use in adolescence and emerging adulthood: evidence from 90 studies and 9441 participants

Cannabis use peaks in adolescence, and adolescents may be more vulnerable to the neural effects of cannabis and cannabis-related harms due to ongoing brain development during this period. In light of ongoing cannabis policy changes, increased availability, reduced perceptions of harm, heightened interest in medicinal applications of cannabis, and drastic increases in cannabis potency, it is essential to establish an understanding of cannabis effects on the developing adolescent brain. This systematic review aims to: (1) synthesize extant literature on functional and structural neural alterations associated with cannabis use during adolescence and emerging adulthood; (2) identify gaps in the literature that critically impede our ability to accurately assess the effect of cannabis on adolescent brain function and development; and (3) provide recommendations for future research to bridge these gaps and elucidate the mechanisms underlying cannabis-related harms in adolescence and emerging adulthood, with the long-term goal of facilitating the development of improved prevention, early intervention, and treatment approaches targeting adolescent cannabis users (CU). Based on a systematic search of Medline and PsycInfo and other non-systematic sources, we identified 90 studies including 9441 adolescents and emerging adults (n = 3924 CU, n = 5517 non-CU), which provide preliminary evidence for functional and structural alterations in frontoparietal, frontolimbic, frontostriatal, and cerebellar regions among adolescent cannabis users. Larger, more rigorous studies are essential to reconcile divergent results, assess potential moderators of cannabis effects on the developing brain, disentangle risk factors for use from consequences of exposure, and elucidate the extent to which cannabis effects are reversible with abstinence. Guidelines for conducting this work are provided.

Medical Cannabis in Pediatric Oncology: Friend or Foe?

The antineoplastic effects of cannabis have been known since 1975. Since the identification of the components of the endogenous cannabinoid system (ECS) in the 1990s, research into the potential of cannabinoids as medicine has exploded, including in anti-cancer research. However, nearly all of this research has been on adults. Physicians and governing bodies remain cautious in recommending the use of cannabis in children, since the ECS develops early in life and data about cannabis exposure in utero show negative outcomes. However, there exist many published cases of use of cannabis in children to treat pediatric epilepsy and chemotherapy-induced nausea and vomiting (CINV) that show both the safety and efficacy of cannabis in pediatric populations. Additionally, promising preclinical evidence showing that cannabis has anti-cancer effects on pediatric cancer warrants further investigation of cannabis' use in pediatric cancer patients, as well as other populations of pediatric patients. This review aims to examine the evidence regarding the potential clinical utility of cannabis as an anti-cancer treatment in children by summarizing what is currently known about uses of medical cannabis in children, particularly regarding its anti-cancer potential.

The Epigenetics of Psychosis: A Structured Review with Representative Loci

The evidence for an environmental component in chronic psychotic disorders is strong and research on the epigenetic manifestations of these environmental impacts has commenced in earnest. In reviewing this research, the focus is on three genes as models for differential methylation, MCHR1, AKT1 and TDO2, each of which have been investigated for genetic association with psychotic disorders. Environmental factors associated with psychotic disorders, and which interact with these model genes, are explored in depth. The location of transcription factor motifs relative to key methylation sites is evaluated for predicted gene expression results, and for other sites, evidence is presented for methylation directing alternative splicing. Experimental results from key studies show differential methylation: for MCHR1, in psychosis cases versus controls; for AKT1, as a pre-existing methylation pattern influencing brain activation following acute administration of a psychosis-eliciting environmental stimulus; and for TDO2, in a pattern associated with a developmental factor of risk for psychosis, in all cases the predicted expression impact being highly dependent on location. Methylation induced by smoking, a confounding variable, exhibits an intriguing pattern for all three genes. Finally, how differential methylation meshes with Darwinian principles is examined, in particular as it relates to the “flexible stem” theory of evolution.

Examining the Use of Antidepressants for Adolescents with Depression/Anxiety Who Regularly Use Cannabis: A Narrative Review

Depression and anxiety disorders are two of the most common and growing mental health concerns in adolescents. Consequently, antidepressant medication (AD) use has increased widely during the last decades. Several classes of antidepressants are used mainly to treat depression, anxiety, and obsessive-compulsive disorders by targeting relevant brain neurochemical pathways. Almost all randomized clinical trials of antidepressants examined patients with no concomitant medications or drugs. This does not address the expected course of therapy and outcome in cannabis users. Cannabis is the most commonly used illicit substance globally. Substantial changes in its regulation are recently taking place. Many countries and US states are becoming more permissive towards its medical and recreational use. The psychological and physiological effects of cannabis (mainly of its major components, tetrahydrocannabinol (THC) and cannabidiol (CBD)) have been extensively characterized. Cannabis use can be a risk factor for depressive and anxiety symptoms, but some constituents or mixtures may have antidepressant and/or anxiolytic potential. The aim of this literature review is to explore whether simultaneous use of AD and cannabis in adolescence can affect AD treatment outcomes. Based on the current literature, it is reasonable to assume that antidepressants are less effective for adolescents with depression/anxiety who frequently use cannabis. The mechanisms of action of antidepressants and cannabis point to several similarities and conjunctions that merit future investigation regarding the potential effectiveness of antidepressants among adolescents who consume cannabis regularly.

Individual and poly-substance use and condomless sex among HIV-uninfected adults reporting heterosexual sex in a multi-site cohort

BACKGROUND

We analyzed the association between substance use (SU) and condomless sex (CS) among HIV-negative adults reporting heterosexual sex in the Seek, Test, Treat, and Retain (STTR) consortium. We describe the impact of SU as well as person/partner and context-related factors on CS, identifying combinations of factors that indicate the highest likelihood of CS.

METHODS

We analyzed data from four US-based STTR studies to examine the effect of SU on CS using two SU exposures: 1) recent SU (within 3 months) and 2) SU before/during sex. Behavioral data were collected via 1:1 or self-administered computerized interviews. Adjusted individual-study, multivariable relative risk regression was used to examine the relationship between CS and SU. We also examined interactions with type of sex and partner HIV status. Pooled effect estimates were calculated using traditional fixed-effects meta-analysis. We analyzed data for recent SU (n = 6781; 82% men, median age = 33 years) and SU before/during sex (n = 2915; 69% men, median age = 40 years).

RESULTS

For both exposure classifications, any SU other than cannabis increased the likelihood of CS relative to non-SU (8-16%, p-values< 0.001). In the recent SU group, however, polysubstance use did not increase the likelihood of CS compared to single-substance use. Cannabis use did not increase the likelihood of CS, regardless of frequency of use. Type of sex was associated with CS; those reporting vaginal and anal sex had a higher likelihood of CS compared to vaginal sex only for both exposure classifications (18-21%, p < 0.001). Recent SU increased likelihood of CS among those reporting vaginal sex only (9-10%, p < 0.001); results were similar for those reporting vaginal and anal sex (5-8%, p < 0.01). SU before/during sex increased the likelihood of CS among those reporting vaginal sex only (20%; p < 0.001) and among those reporting vaginal and anal sex (7%; p = 0.002). Single- and poly-SU before/during sex increased the likelihood of CS for those with exclusively HIV-negative partners (7-8%, p ≤ 0.02), and for those reporting HIV-negative and HIV-status unknown partners (9-13%, p ≤ 0.03).

CONCLUSION

Except for cannabis, any SU increased the likelihood of CS. CS was associated with having perceived HIV-negative partners and with having had both anal/vaginal sex.

Examining the Effectiveness of 3D Virtual Reality Training on Problem-solving, Self-efficacy, and Teamwork Among Inexperienced Volunteers Helping With Drug Use Prevention: Randomized Controlled Trial

BACKGROUND

Illegal drug usage among adolescents is a critical health problem. The Taiwanese government provides an accompanying volunteer program to prevent students who experiment with drugs from reusing them. An appropriate training program can improve volunteers' abilities to assist students using drugs. Problem-solving, self-efficacy, and teamwork are critical abilities for inexperienced volunteers who help with drug use prevention. By interacting with the animation or 3D virtual reality (VR) in the virtual scene, learners can immerse themselves in the virtual environment to learn, and 3D VR can increase learning opportunities and reduce the cost of human and material resources.

OBJECTIVE

The aim of this study was to examine the effectiveness of spherical video-based virtual reality (SVVR) training in improving problem-solving, self-efficacy, and teamwork among volunteers who helped prevent adolescents from using illegal drugs.

METHODS

This study used a randomized controlled design with a total of 68 participants in the experimental (n=35) and control (n=33) groups. The participants in the experimental group received the SVVR training program and their counterparts in the control group did not receive any training.

RESULTS

Generalized estimating equation analyses indicated that the experimental group showed significant posttraining improvements in problem-solving and self-efficacy but not teamwork when compared with the control group.

CONCLUSIONS

The results of this study revealed that SVVR could improve participants' problem-solving skills and self-efficacy for assisting students in not using illegal drugs. However, future studies are suggested to develop effective SVVR to assist inexperienced volunteers in enhancing their teamwork abilities. We believed that introducing the training program to more sites can enhance volunteer training so that volunteers can have a better companionship effect when helping students quit drugs.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05072431; https://clinicaltrials.gov/ct2/show/NCT05072431.

Alcohol and Cannabis Use and the Developing Brain

PURPOSE

Alcohol and cannabis are the most commonly used substances during adolescence and are typically initiated during this sensitive neurodevelopmental period. The aim of this review is to provide a comprehensive overview of the most recent literature focused on understanding how these substances affect the developing brain.

SEARCH METHODS

Articles included in this review were identified by entering 30 search terms focused on substance use, adolescence, and neurodevelopment into MEDLINE, Embase, PsycINFO, ProQuest Central, and Web of Science. Studies were eligible for inclusion if they longitudinally examined the effect of adolescent alcohol and/or cannabis use on structural or functional outcomes in 50 or more participants.

SEARCH RESULTS

More than 700 articles were captured by the search, and 43 longitudinal studies met inclusion criteria, including 18 studies focused on alcohol use, 13 on cannabis use, and 12 on alcohol and cannabis co-use.

DISCUSSION AND CONCLUSIONS

Existing studies suggest heavy alcohol and cannabis use during adolescence are related to small to moderate disruptions in brain structure and function, as well as neurocognitive impairment. The effects of alcohol use include widespread decreases in gray matter volume and cortical thickness across time; slowed white matter growth and poorer integrity; disrupted network efficiency; and poorer impulse and attentional control, learning, memory, visuospatial processing, and psychomotor speed. The severity of some effects is dependent on dose. Heavy to very heavy cannabis use is associated with decreased subcortical volume and increased frontoparietal cortical thickness, disrupted functional development, and decreased executive functioning and IQ compared to non-using controls. Overall, co-use findings suggest more pronounced effects related to alcohol use than to cannabis use. Several limitations exist in the literature. Sample sizes are relatively small and demographically homogenous, with significant heterogeneity in substance use patterns and methodologies across studies. More research is needed to clarify how substance dosing and interactions between substances, as well as sociodemographic and environmental factors, affect outcomes. Larger longitudinal studies, already underway, will help clarify the relationship between brain development and substance use.

Chlorpyrifos and Δ9 Tetrahydrocannabinol exposure and effects on parameters associated with the endocannabinoid system and risk factors for obesity

Marilyn Silva. Retired from a career in toxicology and risk assessment. Increased childhood and adult obesity are associated with chlorpyrifos (CPF), an organophosphate pesticide. Cannabis (Δ9Tetrahydrocannabinol: Δ9THC) use has increased globally with legalization. CPF applications on cannabis crops lacks federally regulated tolerances and may pose health risks through exposure during development and in adulthood. Both CPF and Δ9THC affect the endocannabinoid system (eCBS), a regulator of appetite, energy balance, and gut microbiota, which, if disrupted, increases risk for obesity and related diseases. CPF inhibits eCB metabolism and Δ9THC is a partial agonist/antagonist at the cannabinoid receptor (CB1R). Effects of each on obesogenic parameters were examined via literature search. Male rodents with CPF exposure showed increased body weights, dysbiosis, inflammation and oxidative stress, potentially associated with increased eCBs acting through the gut-microbiota-adipose-brain regulatory loop. Δ9THC generally decreased body weights via partial agonism at the CB1R, lowering levels of eCBs. Dysbiosis and/or oxidative stress associated inflammation occurred with CPF, but these parameters were not tested with Δ9THC. Database deficiencies included limited endpoints to compare between chemicals/age-groups, inter-study variables (dose ranges, dosing vehicle, rodent strain, treatment duration, etc.). CPF and Δ9THC were not tested together, but human co-chemical effects would depend on exposure ratio, subject age, exposure duration, and health status, among others. An overriding concern is that both chemicals are well-documented developmental neurotoxins in addition to their low dose effects on energy balance. A co-exposure risk assessment is warranted with increased use and lack of federal CPF regulation on cannabis.

Promising vulnerability markers of substance use and misuse: A review of human neurobehavioral studies

Substance use often begins, and noticeably escalates, during adolescence. Identifying predictive neurobehavioral vulnerability markers of substance use and related problems may improve targeted prevention and early intervention initiatives. This review synthesizes 44 longitudinal studies and explores the utility of developmental imbalance models and neurobehavioral addiction frameworks in predicting neural and cognitive patterns that are associated with prospective substance use initiation and escalation among young people. A total of 234 effect sizes were calculated and compared. Findings suggest that aberrant neural structure and function of regions implicated in reward processing, cognitive control, and impulsivity can predate substance use initiation, escalation, and disorder. Functional vulnerability markers of substance use include hyperactivation during reward feedback and risk evaluation in prefrontal and ventral striatal regions, fronto-parietal hypoactivation during working memory, distinctive neural patterns during successful (fronto-parietal hyperactivation) and failed response inhibition (frontal hypoactivation), and related cognitive deficits. Structurally, smaller fronto-parietal and amygdala volume and larger ventral striatal volume predicts prospective substance misuse. Taken together, the findings of this review suggest that neurobehavioral data can be useful in predicting future substance use behaviors. Notably, little to no research has empirically tested the underlying assumptions of widely used theoretical frameworks. To improve the reliability and utility of neurobehavioral data in predicting future substance use behaviors, recommendations for future research are provided. This article is part of the special issue on 'Vulnerabilities to Substance Abuse.'

Attitudes toward medical cannabis among family physicians practising in Ontario, Canada: a qualitative research study

BACKGROUND

Medical cannabis has been legally available in Canada since 2001, but its benefits and harms remain uncertain. We explored attitudes toward medical cannabis among family physicians practising in Ontario.

METHODS

Between January and October 2019, we conducted a qualitative study of Ontario family physicians using semistructured telephone interviews. We applied thematic analysis to interview transcripts and identified representative quotes.

RESULTS

Eleven physicians agreed to be interviewed, and 3 themes regarding medical cannabis emerged: reluctance to authorize use, concern over harms and lack of practical knowledge. Participants raised concerns about the limited evidence for, and their lack of education regarding, the therapeutic use of cannabis, particularly the harms associated with neurocognitive development, exacerbation of mental illness and drug interactions in older adults. Some participants thought medical cannabis was overly accessible and questioned their role following legalization of recreational cannabis.

INTERPRETATION

Despite the increasing availability of medical cannabis, family physicians expressed reluctance to authorize its use because of lack of knowledge and concerns regarding harms. Family physicians may benefit from guidance and education that address concerns they have surrounding medical cannabis.

A review investigating the relationship between cannabis use and adolescent cognitive functioning

Given varying state-level laws regarding cannabis use, the objective of the review was to summarize contemporary literature on the relationship between adolescent cognitive function and academic performance with cannabis use. Frequency and quantity of cannabis use were associated with decreased functional connectivity of the brain. Earlier age at cannabis initiation and more frequent use was associated with poorer executive control and academic performance. Social determinants such as minimal parental monitoring, peer use and low social cohesion were associated with more frequent adolescent use. Race/ethnicity and residence were other factors influencing cannabis use. To prevent cannabis use disorders among adolescents, interventions should aim to prevent early initiation that can lead to chronic use in youth who may be more at risk.

Resting State Hypoconnectivity of Reward Networks in Binge Eating Disorder

The clinical presentation of binge eating disorder (BED) and data emerging from task-based functional neuroimaging research suggests that this disorder may be associated with alterations in reward processing. However, there is a dearth of research investigating the functional organization of brain networks that mediate reward in BED. To address this gap, 27 adults with BED and 21 weight-matched healthy controls (WMC) completed a multimodel assessment consisting of a resting functional magnetic resonance imaging scan, behavioral tasks measuring reward-based decision-making (i.e., delay discounting and reversal learning), and self-report assessing clinical symptoms. A seed-based approach was employed to examine the resting state functional connectivity (rsFC) of the striatum (nucleus accumbens [NAcc] and ventral and dorsal caudate), a collection of regions implicated in reward processing. Compared with WMC, the BED group exhibited lower rsFC of striatal seeds, with frontal regions mediating executive functioning (e.g., superior frontal gyrus [SFG]) and posterior, parietal, and temporal regions implicated in emotional processing. Lower NAcc-SFG rsFC was associated with more difficulties with reversal learning and binge eating frequency in the BED group. Results suggest that hypoconnectivity of striatal networks that integrate self-regulation and reward processing may promote the clinical phenomenology of BED. Interventions for BED may benefit from targeting these circuit-based disturbances.

Which came first: Cannabis use or deficits in impulse control?

Impulse control deficits are often found to co-occur with substance use disorders (SUDs). On the one hand, it is well known that chronic intake of drugs of abuse remodels the brain with significant consequences for a range of cognitive behaviors. On the other hand, individual variation in impulse control may contribute to differences in susceptibility to SUDs. Both of these relationships have been described, thus leading to a "chicken or the egg" debate which remains to be fully resolved. Does impulsivity precede drug use or does it manifest as a function of problematic drug usage? The link between impulsivity and SUDs has been most strongly established for cocaine and alcohol use disorders using both preclinical models and clinical data. Much less is known about the potential link between impulsivity and cannabis use disorder (CUD) or the directionality of this relationship. The initiation of cannabis use occurs most often during adolescence prior to the brain's maturation, which is recognized as a critical period of development. The long-term effects of chronic cannabis use on the brain and behavior have started to be explored. In this review we will summarize these observations, especially as they pertain to the relationship between impulsivity and CUD, from both a psychological and biological perspective. We will discuss impulsivity as a multi-dimensional construct and attempt to reconcile the results obtained across modalities. Finally, we will discuss possible avenues for future research with emerging longitudinal data.

Associations of socio-demographic characteristics, well-being, school absenteeism, and substance use with recreational nitrous oxide use among adolescents: A cross-sectional study

PURPOSE

A rapid increase of recreational nitrous oxide use (i.e. laughing gas, N2O) has been reported in several countries, while it has received limited attention in scientific research. We aimed to study the association of socio-demographic characteristics, mental well-being, sickness absence, truancy, and substance use with the frequency of lifetime nitrous oxide use among adolescents.

METHODS

We used self-reported questionnaire data of adolescents (N = 555) attending secondary schools to cross-sectionally assess the frequency of nitrous oxide use and potential factors associated with nitrous oxide use, such as gender, mental well-being, and binge drinking. Ordinal logistic regression models were applied with lifetime nitrous oxide use (never, once, ≥ two times) as the outcome variable.

RESULTS

Adolescents were on average 15.6 years old (SD = 0.83, range 14-18), 47.0% were female. In total, 86 (15.6%) adolescents had used nitrous oxide at least once in their life. In the multivariable ordinal regression model, the risk of having a higher category of lifetime nitrous oxide use was associated with a non-Dutch ethnic background (OR = 2.10, 95% CI 1.22; 3.61), attending pre-vocational education (OR = 1.88, 95% CI 1.06; 3.34), a higher score on the scale of externalizing problems (OR = 1.10, 95% CI 1.01; 1.20), binge drinking twice or more in the past four weeks (OR = 2.49, 95% CI 1.25; 4.94), and cannabis use (OR = 1.98, 95% CI 1.03; 3.79).

CONCLUSIONS

Youth Health Care professionals should be aware of nitrous oxide use in adolescents, especially among adolescents with a non-Dutch ethnic background, lower education levels, externalizing problems, frequent binge drinking, and cannabis use.

Cannabis Use, Cannabis Use Disorder, and Comorbid Psychiatric Illness: A Narrative Review

BACKGROUND

The landscape of attitudes, legal status and patterns of use of cannabis is rapidly changing in the United States and elsewhere. Therefore, the primary aim of this narrative review is to provide a concise overview of the literature on the comorbidity of cannabis use and cannabis use disorder (CUD) with other substance use and psychiatric disorders, and to use this information to accurately guide future directions for the field.

METHODS

A literature review of PubMed was conducted for studies relating to cannabis use, CUD, and a co-occurring psychiatric disorder. To provide an overview of representative data, the literature review focused on national-level, population-based work from the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC) and National Survey on Drug Use and Health (NSDUH) surveys. Considering rapidly changing cannabis laws, recent (past five-year) studies were addressed.

RESULTS

A strong body of literature shows associations between cannabis use and CUD with other drug use, psychosis, mood disorders, anxiety disorders, and personality disorders. The strongest evidence of a potential causal relationship exists between cannabis use and psychotic disorders. While some evidence shows potential directionality between cannabis use and mood and anxiety disorders, results are inconsistent. Studies have established higher rates of CUD among those with personality disorders, but little about the specifics of this relationship is understood.

CONCLUSIONS

Although the general population in the United States increasingly perceives cannabis to be a harmless substance, empirical evidence shows that cannabis use is associated both with CUD and comorbid psychiatric illness. However, there is mixed evidence regarding the role of cannabis in the etiology, course, and prognosis of a co-occurring disorder across all categories of psychiatric disorders. Future research should expand on the existing body of literature with representative, longitudinal data, in order to better understand the acute and long-term effects of cannabis on comorbid psychiatric illness.

Adolescent Substance Use and the Brain: Behavioral, Cognitive and Neuroimaging Correlates

Adolescence is an important ontogenetic period that is characterized by behaviors such as enhanced novelty-seeking, impulsivity, and reward preference, which can give rise to an increased risk for substance use. While substance use rates in adolescence are generally on a decline, the current rates combined with emerging trends, such as increases in e-cigarette use, remain a significant public health concern. In this review, we focus on the neurobiological divergences associated with adolescent substance use, derived from a cross-sectional, retrospective, and longitudinal studies, and highlight how the use of these substances during adolescence may relate to behavioral and neuroimaging-based outcomes. Identifying and understanding the associations between adolescent substance use and changes in cognition, mental health, and future substance use risk may assist our understanding of the consequences of drug exposure during this critical window.

Trends of the incidence of drug use disorders from 1990 to 2017: an analysis based on the Global Burden of Disease 2017 data

AIM

Drug use disorders are an important issue worldwide. Systematic attempts to estimate the global incidence of drug use disorders are rare. We aimed to determine the incidence of drug use disorders and their trends.

METHODS

We obtained the annual incident cases and age-standardised incidence rate (ASR) of drug use disorders from 1990 to 2017 using the Global Health Data Exchange query tool. The estimated annual percentage changes of the ASR were used to quantify and evaluate the trends in the incidence rate. Gaussian process regression and the Pearson's correlation coefficient were used to assess the relationship between the ASR and socio-demographic index (SDI).

RESULTS

The number of drug use disorders' cases increased by 33.5% from 1990 to 2017 globally, whereas the ASR exhibited a stable trend. The ASR was higher in men than in women. Most cases (53.1%) of drug use disorders involved opioid. A positive association (ρ=0.35, p < 0.001) was found between ASR and SDI. Teenagers aged 15-19 years had the highest incidence rate.

CONCLUSIONS

The incident cases of drug use disorders were increasing, but the incidence rate did not change significantly from 1990 to 2017. Current preventive measures and policies for drug use disorders might have little effect. The present results suggest that future strategies should focus on men, teenagers and high-risk regions in order to improve the current status of drug use disorders.

Assessing the public health impact of cannabis legalization in Canada: core outcome indicators towards an 'index' for monitoring and evaluation

The legalization of non-medical cannabis use and supply is impending in Canada. This constitutes a major policy change with the declared objective of improving public health outcomes, which requires rigorous monitoring and evaluation. While numerous different aspects associated with legalization will be examined, a focused perspective is required for effective policy evaluation purposes. To these ends, we have identified a set of 10 core indicators associated with cannabis-related risk/harm outcomes-based on current best evidence-that are expected to measure the primary impacts of legalization on public health outcomes. We briefly review these indicators, and their respective data availability in Canada. As ideally an integrated outcome assessment of cannabis legalization's impact on public health will be available, we further propose options to merge the individual indicators into an integrated, weighted 'index', considering their expected relative impact for public health. One possible approach to undertake this is 'multi-criteria decision analysis' as a method to weight the relative indicator impact on public health; alternative approaches are proposed. The integrated 'public health index' for cannabis legalization will allow for scientifically comprehensive, while focused, monitoring and evaluation of the effects of legalization in Canada for the benefits of science and evidence-based policy alike.

Cannabis Use in Adolescence: A Review of Neuroimaging Findings

Objective: Shifting policies and widespread acceptance of cannabis for medical and/or recreational purposes have fueled worries of increased cannabis initiation and use in adolescents. In particular, the adolescent period is thought to be associated with an increased susceptibility to the potential harms of repeated cannabis use, due to being a critical period for neuromaturational events in the brain. This review investigates the neuroimaging evidence of brain harms attributable to adolescent cannabis use. Methods: PubMed and Scopus searches were conducted for empirical articles that examined neuroimaging effects in both adolescent cannabis users and adult user studies that explored the effect of age at cannabis use onset on the brain. Results: We found 43 studies that examined brain effect (structural and functional magnetic resonance imaging) in adolescent cannabis users and 20 that examined the link between onset age of cannabis use and brain effects in adult users. Studies on adolescent cannabis users relative to nonusers mainly implicate frontal and parietal regions and associated brain activation in relation to inhibitory control, reward, and memory. However, studies in adults are more mixed, many of which did not observe an effect of onset age of cannabis use on brain imaging metrics. Conclusions: While there is some evidence of compromised frontoparietal structure and function in adolescent cannabis use, it remains unclear whether the observed effects are specifically attributable to adolescent onset of use or general cannabis use-related factors such as depressive symptoms. The relative contribution of adolescent onset of cannabis use and use chronicity will have to be more comprehensively examined in prospective, longitudinal studies with more rigorous measures of cannabis use (dosage, exposure, dependence, constituent compounds such as the relative cannabinoid levels).

Is the Adolescent Brain at Greater Vulnerability to the Effects of Cannabis? A Narrative Review of the Evidence

Cannabis use during the critical neurodevelopmental period of adolescence, may lead to brain structural, functional, and histological alterations that may underpin some of the longer-term behavioral and psychological harms associated with it. The endocannabinoid system performs a key regulatory and homeostatic role, that undergoes developmental changes during adolescence making it potentially more susceptible to the effects of exposure to cannabis during adolescence. Here, we synthesize evidence from human studies of adolescent cannabis users showing alterations in cognitive performance as well as in brain structure and function with relevant preclinical evidence to summarize the current state of knowledge. We also focus on the limited evidence that speaks to the hypothesis that cannabis use during adolescence, may pose a greater risk than use during adulthood, identify gaps in current evidence and suggest directions for new research. Existing literature is consistent with the association of cannabis use during adolescence and neurological changes. Adolescence cannabis users show altered functional connectivity within known functional circuits, that may underlie inefficient recruitment of brain regions, as largely increased functional activation has been observed compared to controls. This disruption in some cases may contribute to the development of adverse mental health conditions; increasing the chances or accelerating the onset, of their development. Preclinical evidence, further supports disruption from cannabis use being specific to the developmental period. Future studies are required to better investigate adolescent cannabis use with more accuracy using better defined groups or longitudinal studies and examine the permanency of these changes following caseation of use. Furthermore, research is required to identify heritable risk factors to cannabis use. There is a need for caution when considering the therapeutic potential of cannabis for adolescence and particularly in public discourse leading to potential trivialization of possible harm from cannabis use in adolescence. Current evidence indicates that adolescence is a sensitive period during which cannabis use may result in adverse neurocognitive effects that appear to show a level of permanency into adulthood.

Adolescent Brain Surface Area Pre- and Post-Cannabis and Alcohol Initiation

OBJECTIVE

Changes in gray matter volume and thickness are associated with adolescent alcohol and cannabis use, but the impact of these substances on surface area remains unclear. The present study expands on previous findings to examine the impact of alcohol and cannabis on surface area before and after use initiation.

METHOD

Scans for 69 demographically similar youth were obtained at baseline (ages 12-14 years; before substance use) and at 6-year follow-up (ages 17-21 years). Participants were classified into three groups based on substance use: alcohol use initiators (ALC, n = 23), alcohol and cannabis use initiators (ALC+CU, n = 23), and individuals with minimal substance use (<3 lifetime alcohol and 0 marijuana use episodes; CON, n = 23). For each hemisphere, group differences in surface area across time (pre- and post-substance use initiation) and significant group-by-time interactions were examined individually for 34 cortical regions using repeated measures analysis of covariance. A vertex-wise analysis assessed group differences in surface area percent change.

RESULTS

A significant group-by-time interaction was found in three regions, bilateral medial orbitofrontal cortices and right insula. Although all regions showed decreases in surface area over time (ps < .05), a more substantial decrease was identified in the ALC group. Of note, the right medial orbitofrontal cortex survived the conservative vertex-wise analyses (p < .001), as a more substantial decrease was found in the ALC compared to the ALC+CU group in this region.

CONCLUSIONS

Surface area in the medial orbitofrontal cortex may be a useful intermediate phenotype for exploring the mechanisms underlying the effects of substance use on brain development.

Orbitofrontal cortex volume prospectively predicts cannabis and other substance use onset in adolescents

BACKGROUND

Identifying neural characteristics that predict cannabis initiation is important for prevention efforts. The orbitofrontal cortex is critical for reward response and may be vulnerable to substance-induced alterations.

AIMS

We measured orbitofrontal cortex thickness, surface area, and volume prior to the onset of use to predict cannabis involvement during an average nine-year follow-up.

METHODS

Adolescents (n=118) aged 12-15 years completed baseline behavioral assessment and magnetic resonance imaging scans, then were followed up to 13 years with annual substance use interviews. Logistic regression examined baseline (pre-substance use) bilateral medial and lateral orbitofrontal cortex characteristics (volume, surface area, or cortex thickness) as predictors of regular cannabis use by follow-up. Post-hoc multinomial logistic regression assessed whether orbitofrontal cortex characteristics significantly predicted either alcohol use alone or cannabis+alcohol co-use. Brain-behavior relationships were assessed through follow-up correlations of baseline relationships between orbitofrontal cortex and executive functioning, reward responsiveness, and behavioral approach traits.

RESULTS

Larger left lateral orbitofrontal cortex volume predicted classification as cannabis user by follow-up (p=0.025, odds ratio=1.808). Lateral orbitofrontal cortex volume also predicted cannabis+alcohol co-user status (p=0.008, odds ratio=2.588), but not alcohol only status. Larger lateral orbitofrontal cortex volume positively correlated with greater baseline reward responsiveness (p=0.030, r=0.348). There were no significant results by surface area or cortex thickness (ps>0.05).

CONCLUSIONS

Larger left lateral orbitofrontal cortex measured from ages 12-15 years and prior to initiation of substance use was related to greater reward responsiveness at baseline and predicted classification as a cannabis user and cannabis+alcohol co-user by final follow-up. Larger lateral orbitofrontal cortex volume may represent aberrant orbitofrontal cortex maturation and increasing vulnerability for later substance use.

Chronic cannabis use and circulating biomarkers of neural health, stress, and inflammation in physically active individuals

Previous research has associated cannabis use with altered circulating neurotrophins and biomarkers of immune health, but these relationships have yet to be fully explored in physically active individuals. The specific aim of this study was to explore the relationships between biomarkers of neural health: nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), immune health: interleukin 6 (IL-6), C-reactive protein (CRP), and cortisol, as well as the presence of depression, in physically active cannabis users (CU) and nonusers (NU). Male and female participants (N = 30; CU, n = 15, NU, n = 15) provided intravenous blood samples and underwent assessment of body composition, maximal oxygen consumption, and depression (Beck Depression Inventory-II (BDI-II)). Samples were analyzed for concentrations of NGF, BDNF, IL-6, CRP, and cortisol using ELISAs. CU and NU were compared using an unpaired t test. Pearson's correlation and multiple linear regression were used to evaluate relationships among variables. There were no significant differences in body size or composition, maximal oxygen consumption, total BDI-II Score, concentrations of NGF, IL-6, CRP, or cortisol between groups. BDNF was significantly lower in CU compared with NU (p = 0.02), with a significant negative relationship between BDNF and CRP (p = 0.02). Mean concentrations of CRP placed CU at higher risk for cardiovascular disease compared with NU. Total BDI-II score negatively correlated with BDNF (p = 0.02) and positively correlated with CRP (p = 0.02). Novelty Plasma BDNF was significantly lower in physically active cannabis users compared with NU. CU were classified at moderate risk for cardiovascular disease based on average circulating CRP compared with low risk for NU.

Navigating Blind in the Green Rush: Clinical Considerations and Harm Reduction Practices for Cannabis

Background

The United States has recently experienced extensive changes in state policy regarding the use of cannabis for recreational and medicinal purposes. Despite its rapidly increasing accessibility and social acceptance, there is a striking dearth of research on cannabis as a treatment for medical and psychological conditions. Research on cannabis is difficult to conduct as it is classified as a schedule I drug with high potential for abuse and currently no accepted medical use in treatment. As a result, no standard dosing procedures exist and the lack of conclusive scientific evidence has left clinical providers without evidence-based guidelines about if, when, and how to guide clients on using cannabis safely.

Objective

To (1) provide critical psychoeducational information about cannabis and cannabis problems to guide client-provider conversations about cannabis use and (2) describe common clinical concerns around cannabis use, highlight special considerations for vulnerable populations, and review harm reduction techniques and practical resources that may help clinicians and their clients navigate safer cannabis use.

Conclusion

The removal of regulatory barriers would enable researchers to address key public health questions about the potential therapeutic and adverse effects of cannabis use. Additionally, funds for research, clinician education, and public health education initiatives are necessary to reduce risk around cannabis use in the United States.

Legalized Cannabis in Colorado Emergency Departments: A Cautionary Review of Negative Health and Safety Effects

Cannabis legalization has led to significant health consequences, particularly to patients in emergency departments and hospitals in Colorado. The most concerning include psychosis, suicide, and other substance abuse. Deleterious effects on the brain include decrements in complex decision-making, which may not be reversible with abstinence. Increases in fatal motor vehicle collisions, adverse effects on cardiovascular and pulmonary systems, inadvertent pediatric exposures, cannabis contaminants exposing users to infectious agents, heavy metals, and pesticides, and hash-oil burn injuries in preparation of drug concentrates have been documented. Cannabis dispensary workers (“budtenders”) without medical training are giving medical advice that may be harmful to patients. Cannabis research may offer novel treatment of seizures, spasticity from multiple sclerosis, nausea and vomiting from chemotherapy, chronic pain, improvements in cardiovascular outcomes, and sleep disorders. Progress has been slow due to absent standards for chemical composition of cannabis products and limitations on research imposed by federal classification of cannabis as illegal. Given these factors and the Colorado experience, other states should carefully evaluate whether and how to decriminalize or legalize non-medical cannabis use.

Predicting latent classes of drug use among adolescents through parental alcohol use and parental style: a longitudinal study

PURPOSE

The present study examined the roles of parental alcohol use and parental style as predictors of adolescent patterns of drug use.

METHODS

6391 students in the 7th and 8th grades at 72 Brazilian public schools participated in a three-wave randomized controlled trial to evaluate a school drug-use prevention program. Patterns of drug use were identified through two latent class analyses using measures of the adolescents' past-year drug use. Multinomial logistic regression analyses examined whether parental alcohol use and parenting style at baseline predicted patterns of drug use in waves 2 and 3 of the study after controlling for sociodemographic covariates.

RESULTS

In each of the two waves, three latent classes of drug use were identified among the students, defining three different groups of individuals: (1) abstainers/low users, (2) alcohol users/binge drinkers, and (3) polydrug users. First, parenting style (especially monitoring) was the strongest predictor for the prevention of polydrug use among adolescents. Second, occasional alcohol use by parents can act as a central predictor for adolescent alcohol use and binge drinking. Above all, maternal episodes of drunkenness were involved in the predictive models for both drug use classes in both waves.

CONCLUSION

Parental alcohol use and parenting style seem to be important predictors of adolescent's likelihood of belonging to different latent classes of drug use. This conclusion may point to the importance of considering the inclusion of parenting skills and parental alcohol use within the scope of adolescents' preventive interventions.

Longitudinal Alterations in Prefrontal Resting Brain Connectivity in Non-Treatment-Seeking Young Adults With Cannabis Use Disorder

Background: Cannabis is increasingly perceived as a harmless drug by recreational users, yet chronic use may impact brain changes into adulthood. Repeated cannabis exposure has been associated with enduring synaptic changes in executive control and reward networks. It is important to determine whether there are brain functional alterations within these networks in individuals that do not seek treatment for chronic cannabis abuse. Methods: This longitudinal study compared resting-state functional connectivity changes in executive control and reward networks between 23 non-treatment-seeking young adults with cannabis use disorder (6 females; baseline age M = 19.3 ± 1.18) and 21 age-matched controls (10 females; baseline age M = 19.4 ± 0.65) to determine group differences in the temporal trajectories of resting-state functional connectivity across a 2-year span. Results: Results showed i) significant increases in resting-state functional connectivity between the caudal anterior cingulate cortex and precentral and parietal regions over time in the control group, but not in the cannabis use disorder group, and ii) sustained lower resting-state functional connectivity of anterior cingulate cortex seeds with frontal and thalamic regions in the cannabis use disorder group vs. the age-matched controls. Resting-state functional connectivity strength was correlated with cannabis use patterns in the cannabis use disorder sample. Conclusion: Longitudinal alterations in intrinsic functional organization of executive control networks found in non-treatment-seeking young adults with cannabis use disorder (when compared to age-matched controls) may impact regulatory control over substance use behavior. Current findings were limited to examining executive control and reward networks seeded in ACC and NAcc, respectively. Future studies with larger sample sizes and enough power are needed to conduct exploratory analyses examining rsFC of other networks beyond those within the scope of the current study.

The neuropsychopharmacology of cannabis: A review of human imaging studies

The laws governing cannabis are evolving worldwide and associated with changing patterns of use. The main psychoactive drug in cannabis is Δ⁹-tetrahydrocannabinol (THC), a partial agonist at the endocannabinoid CB₁ receptor. Acutely, cannabis and THC produce a range of effects on several neurocognitive and pharmacological systems. These include effects on executive, emotional, reward and memory processing via direct interactions with the endocannabinoid system and indirect effects on the glutamatergic, GABAergic and dopaminergic systems. Cannabidiol, a non-intoxicating cannabinoid found in some forms of cannabis, may offset some of these acute effects. Heavy repeated cannabis use, particularly during adolescence, has been associated with adverse effects on these systems, which increase the risk of mental illnesses including addiction and psychosis. Here, we provide a comprehensive state of the art review on the acute and chronic neuropsychopharmacology of cannabis by synthesizing the available neuroimaging research in humans. We describe the effects of drug exposure during development, implications for understanding psychosis and cannabis use disorder, and methodological considerations. Greater understanding of the precise mechanisms underlying the effects of cannabis may also give rise to new treatment targets.

The long-term cognitive consequences of adolescent exposure to recreational drugs of abuse

During adolescence, the brain continues to undergo vital developmental processes. In turn, complex behavioral and cognitive skills emerge. Unfortunately, neurobiological development during adolescence can be influenced by environmental factors such as drug exposure. Engaging in drug use during adolescence has been a long-standing health concern, especially how it predicts or relates to drug using behavior later in life. However, recent findings suggest that other behavioral domains, such as learning and memory, are also vulnerable to adolescent drug use. Moreover, it is becoming increasingly apparent that deficits in learning and memory following adolescent drug use endure into adulthood, well after drug exposure has subsided. Although persistent effects suggest an interaction between drug exposure and ongoing development during adolescence, the exact acute and long-term consequences of adolescent drug exposure on substrates of learning and memory are not fully understood. Thus, this review will summarize human and animal findings on the enduring cognitive deficits due to adolescent drug exposure. Moreover, due to the fact that adolescents are more likely to consume drugs of abuse legally available to adults, this review will focus on alcohol, nicotine, and marijuana. Further, given the critical role of the frontal cortex and hippocampus in various learning and memory domains, the impact adolescent use of the previous listed drugs on the neurobiology within these regions will also be discussed.

Convergent neurobiological predictors of emergent psychopathology during adolescence

The adolescent brain undergoes significant structural and functional development. Through the use of magnetic resonance imaging in adolescents, it has been demonstrated that the prefrontal cortex, pertinent for executive control, demonstrates protracted development compared to limbic structures, active during emotion and reward processing. This asynchronous development creates a sensitive window during adolescence, in which many psychopathological disorders (i.e., mental health and substance use) emerge. This review outlines longitudinal studies that use magnetic resonance imaging to identify neurobiological predictors of emergent psychopathology (depression, anxiety, and substance use), during adolescence. Studies identifying neurobiological markers that predict onset and escalation of these disorders, as well as those that predict successful treatment outcomes are explored. An emphasis is placed on frontolimbic brain structures, a convergent neurobiological target for both emergent mental health issues and emergent substance use. The literature reviewed herein suggests that reduced volume and cortical thickness in frontolimbic regions, as well as reduced functional activation (particularly during task involving reward or emotional stimuli) in these regions, may serve as a neurobiological predictors of emergent psychopathology in adolescence. This knowledge is crucial, as it may be used to develop neurobiologically targeted prevention and intervention strategies for youth who are at-risk for developing these psychopathologies.

Marijuana use among adolescent multiple tobacco product users and unique risks of dual tobacco and marijuana use

BACKGROUND

Adolescence is a peak time for uptake of both tobacco and marijuana (dual use). This study aimed to identify clusters of lifetime tobacco and marijuana use patterns and associated risk factors, and to determine whether dual tobacco and marijuana use is uniquely associated with greater risk than use of either tobacco or marijuana alone.

METHOD

High school students participated in a survey during Fall 2014 (N = 976; 68% Hispanic; 57% parental education < high school). Items from national youth surveys were used to measure lifetime and current use of tobacco products, marijuana, alcohol, drug use, and other risk behaviors, and literature-based surveys were used to measure psychological constructs.

RESULTS

Latent Class Analysis identified three clusters of lifetime tobacco use patterns (no tobacco, one or two products, and more than two products), each with a correspondingly distinct profile of risk behaviors; risk escalated with use of more tobacco products. Multinomial modeling characterized personal, environmental, and behavioral correlates of dual lifetime tobacco and marijuana use, including lower parental monitoring, lower grades, higher guilt, higher lifetime alcohol and drug use, and more substance use by friends, in reference to single lifetime use of either tobacco or marijuana.

CONCLUSION

Broader use of tobacco (i.e., more products) was associated with numerous risk factors. Dual lifetime use of tobacco and marijuana was associated with numerous risks compared to single use of either tobacco or marijuana. Longitudinal work is needed to understand temporal relationships between risk variables to determine optimal timing for interventions to reduce harmful behaviors.

Planting the seed for marijuana use: Changes in exposure to medical marijuana advertising and subsequent adolescent marijuana use, cognitions, and consequences over seven years

BACKGROUND

Marijuana use during adolescence is associated with neurocognitive deficits and poorer functioning across several domains. It is likely that more states will pass both medical and recreational marijuana legalization laws in the coming elections; therefore, we must begin to look more closely at the longitudinal effects of medical marijuana (MM) advertising on marijuana use among adolescents so that we can better understand effects that this advertising may have on their subsequent marijuana use and related outcomes.

METHODS

We followed two cohorts of 7th and 8th graders (mean age 13) recruited from school districts in Southern California from 2010 until 2017 (mean age 19) to examine effects of MM advertising on adolescents' marijuana use, cognitions, and consequences over seven years. Latent growth models examined trajectories of self-reported exposure to medical marijuana ads in the past three months and trajectories of use, cognitions, and consequences.

RESULTS

Higher average exposure to MM advertising was associated with higher average use, intentions to use, positive expectancies, and negative consequences. Similarly, higher rates of change in MM advertising exposure were associated with higher rates of change in use, intentions, expectancies, and consequences over seven years.

CONCLUSIONS

Results suggest that exposure to MM advertising may not only play a significant role in shaping attitudes about marijuana, but may also contribute to increased marijuana use and related negative consequences throughout adolescence. This highlights the importance of considering regulations for marijuana advertising, similar to regulations in place for the promotion of tobacco and alcohol in the U.S.

Extend, Pathomechanism and Clinical Consequences of Brain Volume Changes in Anorexia Nervosa

INTRODUCTION

Brain volume deficits of grey matter (GM) and white matter (WM) are often found in patients with anorexia nervosa (AN). However, until recently, little was known about the influencing factors of these brain volume alterations, nor their exact quantification and rehabilitation.

METHODS

This review addresses these open questions and further explores what is now known about the underlying pathobiology and the clinical consequences including human studies as well as animal studies mimicking anorexia nervosa in rodents.

RESULTS

GM was reduced by 3.7% in adults and 7.6% in adolescents with AN. WM was reduced on average 2.2% in adult patients and 3.2% in adolescents. Most volume deficits in adults are reversible after long-term recovery; for adolescents, data are less clear. The main influencing factors for GM were absolute lowest weight at admission and illness duration. Cerebellar and WM reductions at admission predicted clinical outcome at one year follow-up. New studies found GABA receptor changes in GM and astrocyte loss in both GM and WM, as well as a possible role for oestrogen deficit. All three could partly explain clinical symptoms of anxiety, rigidity and learning impairments in patients with AN.

CONCLUSION

Brain volume deficits in AN seem to play a causal role in the course and the prognosis of AN. A better understanding of these brain changes could lead to more targeted therapies for patients with AN, including astrocyte-directed approaches.

Understanding Rates of Marijuana Use and Consequences Among Adolescents in a Changing Legal Landscape

PURPOSE OF REVIEW

There is not one answer to address whether marijuana use has increased, decreased, or stayed the same given changes in state legalization of medical and non-medical marijuana in the USA.

RECENT FINDINGS

Evidence suggests some health benefits for medical marijuana; however, initiation of marijuana use is a risk factor for developing problem cannabis use. Though use rates have remained stable over recent years, about one in three 10th graders report marijuana use, most adolescents do not view the drug as harmful, and over 650,000 youth aged 12 to 17 struggle with cannabis use disorder.

SUMMARY

Although the health benefits of medical marijuana are becoming better understood, more research is needed. Intervention and prevention programs must better address effects of marijuana, acknowledging that while there may be some benefits medically, marijuana use can affect functioning during adolescence when the brain is still developing.

The consequences of chronic cannabis smoking in vulnerable adolescents

Cannabis, like the mythic shape-shifter, presents in various guises, morphing with the perspective and context of the observer. Arguments about cannabis are confused by a myriad of debates-medical, social, ethical and political-as if a single conceptual umbrella can capture the variety and granularity of marijuana-related issues. This paper responds to marijuana use as it is commonly practised by youth in Australia. It has little to say about synthetic cannabinoids, specific medicinal cannabinoids, or medicinal properties of marijuana. We address those adolescents genetically and environmentally vulnerable to mental illness, with specific emphasis on indigenous and neurodevelopmentally impaired young people who show patterns of usage and response very different to adults and more resilient members of the population. Specifically, the practice of mixing tobacco with marijuana by aboriginal youth, and the resultant coalition of dependencies, will likely presage a rise in pulmonary and central nervous system pathology over the coming decades. Aboriginal youth begin using earlier, persist longer, and take greater quantities of cannabis than non-indigenous youth. This paper recommends practical interventions to reduce the multiple health consequences of chronic cannabis use in young people, especially indigenous young people.

Regular cannabis and alcohol use is associated with resting-state time course power spectra in incarcerated adolescents

Cannabis and alcohol are believed to have widespread effects on the brain. Although adolescents are at increased risk for substance use, the adolescent brain may also be particularly vulnerable to the effects of drug exposure due to its rapid maturation. Here, we examined the association between cannabis and alcohol use duration and resting-state functional connectivity in a large sample of male juvenile delinquents. The present sample was drawn from the Southwest Advanced Neuroimaging Cohort, Youth sample, and from a youth detention facility in Wisconsin. All participants were scanned at the maximum-security facilities using The Mind Research Network's 1.5T Avanto SQ Mobile MRI scanner. Information on cannabis and alcohol regular use duration was collected using self-report. Resting-state networks were computed using group independent component analysis in 201 participants. Associations with cannabis and alcohol use were assessed using Mancova analyses controlling for age, IQ, smoking and psychopathy scores in the complete case sample of 180 male juvenile delinquents. No associations between alcohol or cannabis use and network spatial maps were found. Longer cannabis use was associated with decreased low frequency power of the default mode network, the executive control networks (ECNs), and several sensory networks, and with decreased functional network connectivity. Duration of alcohol use was associated with decreased low frequency power of the right frontoparietal network, salience network, dorsal attention network, and several sensory networks. Our findings suggest that adolescent cannabis and alcohol use are associated with widespread differences in resting-state time course power spectra, which may persist even after abstinence.

Sex Differences in Contraception Non-Use Among Urban Adolescents: Risk Factors for Unintended Pregnancy

BACKGROUND

Contraception non-use among sexually active adolescents is a major cause of unintended pregnancy (UP).

METHODS

In this cross-sectional study we sought to identify overall and sex-specific correlates of contraception non-use using the 2015 Philadelphia Youth Risk Behavior Survey (YRBS) (N = 9540). Multivariate regression models were used to examine mental health, sexual activity, substance use, and violence indicators on reported contraception non-use among sexually active youth.

RESULTS

Marijuana use among boys and girls was a statistically significant risk factor for contraception non-use. Availability of illegal drugs on school property in the past year was also significantly related to contraception non-use among boys.

CONCLUSIONS

These results may inform overall and sex-specific adolescent programs to promote consistent contraception use among urban youth within school-based communities.

Lower-Risk Cannabis Use Guidelines: A Comprehensive Update of Evidence and Recommendations

BACKGROUND

Cannabis use is common in North America, especially among young people, and is associated with a risk of various acute and chronic adverse health outcomes. Cannabis control regimes are evolving, for example toward a national legalization policy in Canada, with the aim to improve public health, and thus require evidence-based interventions. As cannabis-related health outcomes may be influenced by behaviors that are modifiable by the user, evidence-based Lower-Risk Cannabis Use Guidelines (LRCUG)-akin to similar guidelines in other health fields-offer a valuable, targeted prevention tool to improve public health outcomes.

OBJECTIVES

To systematically review, update, and quality-grade evidence on behavioral factors determining adverse health outcomes from cannabis that may be modifiable by the user, and translate this evidence into revised LRCUG as a public health intervention tool based on an expert consensus process.

SEARCH METHODS

We used pertinent medical search terms and structured search strategies, to search MEDLINE, EMBASE, PsycINFO, Cochrane Library databases, and reference lists primarily for systematic reviews and meta-analyses, and additional evidence on modifiable risk factors for adverse health outcomes from cannabis use.

SELECTION CRITERIA

We included studies if they focused on potentially modifiable behavior-based factors for risks or harms for health from cannabis use, and excluded studies if cannabis use was assessed for therapeutic purposes.

DATA COLLECTION AND ANALYSIS

We screened the titles and abstracts of all studies identified by the search strategy and assessed the full texts of all potentially eligible studies for inclusion; 2 of the authors independently extracted the data of all studies included in this review. We created Preferred Reporting Items for Systematic Reviews and Meta-Analyses flow-charts for each of the topical searches. Subsequently, we summarized the evidence by behavioral factor topic, quality-graded it by following standard (Grading of Recommendations Assessment, Development, and Evaluation; GRADE) criteria, and translated it into the LRCUG recommendations by the author expert collective on the basis of an iterative consensus process.

MAIN RESULTS

For most recommendations, there was at least "substantial" (i.e., good-quality) evidence. We developed 10 major recommendations for lower-risk use: (1) the most effective way to avoid cannabis use-related health risks is abstinence, (2) avoid early age initiation of cannabis use (i.e., definitively before the age of 16 years), (3) choose low-potency tetrahydrocannabinol (THC) or balanced THC-to-cannabidiol (CBD)-ratio cannabis products, (4) abstain from using synthetic cannabinoids, (5) avoid combusted cannabis inhalation and give preference to nonsmoking use methods, (6) avoid deep or other risky inhalation practices, (7) avoid high-frequency (e.g., daily or near-daily) cannabis use, (8) abstain from cannabis-impaired driving, (9) populations at higher risk for cannabis use-related health problems should avoid use altogether, and (10) avoid combining previously mentioned risk behaviors (e.g., early initiation and high-frequency use).

AUTHORS' CONCLUSIONS

Evidence indicates that a substantial extent of the risk of adverse health outcomes from cannabis use may be reduced by informed behavioral choices among users. The evidence-based LRCUG serve as a population-level education and intervention tool to inform such user choices toward improved public health outcomes. However, the LRCUG ought to be systematically communicated and supported by key regulation measures (e.g., cannabis product labeling, content regulation) to be effective. All of these measures are concretely possible under emerging legalization regimes, and should be actively implemented by regulatory authorities. The population-level impact of the LRCUG toward reducing cannabis use-related health risks should be evaluated. Public health implications. Cannabis control regimes are evolving, including legalization in North America, with uncertain impacts on public health. Evidence-based LRCUG offer a potentially valuable population-level tool to reduce the risk of adverse health outcomes from cannabis use among (especially young) users in legalization contexts, and hence to contribute to improved public health outcomes.

Electronic cigarette and marijuana use among youth in the United States

BACKGROUND

There are growing concerns over the high rate of electronic cigarette (e-cigarette) use and decreases in perceived harm of marijuana use among youth. We seek to identify risk factors associated with e-cigarette and marijuana use among U.S. middle and high school students.

METHODS

Estimates of e-cigarette use only, marijuana use only, dual use of both substances as well as frequency of substance use were calculated for 8th, 10th and 12th grades with the typical age of 13, 15, 17 years old respectively by using the 2014 Monitoring the Future survey (n=16,184).

RESULTS

Overall, 7.9% of students only used e-cigarettes, 9.3% of students only used marijuana, and 6.6% of students used both e-cigarettes and marijuana in the last 30days. E-cigarette use only was most prevalent among 8th and 10th graders while marijuana use only was most prevalent among 12th graders. The dual use of e-cigarettes and marijuana rapidly increased from 8th graders (2.6%) to 10th graders (7.3%) and maintained a high level for 12th graders (8.5%). Students' sociodemographic factors, school performance and work intensity were associated with e-cigarette and marijuana use in the multivariate analysis. Being a dual user of e-cigarettes and marijuana was associated with increased risk of a medium level or a high level of e-cigarette use and a medium level of marijuana use CONCLUSIONS: This study raised the possibility that youth start to use e-cigarettes at an earlier age and then progress to other substances. Education campaigns with tailored messages to prevent youth from vaping and drug use are critically needed.

Individual and contextual factors associated with tobacco, alcohol, and cannabis use among Chilean adolescents: A multilevel study

We studied the association between individual and contextual variables and the use of tobacco, alcohol, or cannabis in the last 30 days preceding the study, considering the hierarchical nature of students nested in schools. We used the 7th Chilean National School Survey of Substance Use (2007) covering 45,273 students (aged 12-21 years old) along with information from 1465 schools provided by the Chilean Ministry of Education. Multilevel univariable and multivariable logistic regression models were performed. We found a significant intra-class correlation within schools for all substances in the study. Common (e.g., availability of pocket money, more time spent with friends, poor parental monitoring, poor school bonding, bullying others, and lower risk perception of substance use) and unique predictors (e.g., school achievement on national tests) were identified. These findings may help in planning and conducting preventive interventions to reduce substance use.

The design of medical marijuana laws and adolescent use and heavy use of marijuana: Analysis of 45 states from 1991 to 2011

OBJECTIVES

To assess the association between U.S. state medical marijuana laws (MML), the most liberal category of marijuana policies before legalization, their specific provisions, and adolescent past-30-day use and heavy marijuana use.

METHODS

This quasi-experimental study used state Youth Risk Behavior Survey (YRBS) data collected during 1991-2011 from 45 states (N=715,014) to examine MML effects, taking advantage of heterogeneity across states in MML status and design. Multiple logistic regression modeling was used to adjust for state and year effects, and youth demographics.

RESULTS

Unadjusted analyses found that MMLs were associated with higher rates of adolescent past-30-day marijuana use (odds ratio [OR]=1.08, 95% confidence interval, [(CI)=1.03,1.13]) and heavy marijuana use (OR=1.12, [CI=1.05,1.21]). However, analyses adjusting for state/year effects found a 7% lower odds of use (OR=0.99, [CI=0.98,0.999]) and no difference in heavy use. In the adjusted models, years since MML enactment (OR=0.93, [CI=0.86,0.99]) and MML inclusion of more liberalized provisions (OR=0.98, [CI=0.96,0.998]) were associated with slightly lowered odds of past-30-day marijuana use. Conversely, allowance for ≥2.5 usable marijuana ounces was associated with higher past-30-day marijuana use odds (OR=1.21, [CI=1.09,1.34]) and a voluntary vs. mandatory patient registration with higher odds of both past-30-day use (OR=1.41, [CI=1.28,1.56]) and heavy use (OR=1.23, [CI=1.08,1.40]).

CONCLUSIONS

MML enactment, years since enactment, and inclusion of more liberalized provisions were not associated with increased adolescent marijuana use in this dataset after adjusting for state and year effects; however, higher possession limits and a voluntary registration were. It is possible that state norms are the impetus for MML enactment.

Neurobiological signatures associated with alcohol and drug use in the human adolescent brain

Magnetic resonance (MR) techniques provide opportunities to non-invasively characterize neurobiological milestones of adolescent brain development. Juxtaposed to the critical finalization of brain development is initiation of alcohol and substance use, and increased frequency and quantity of use, patterns that can lead to abuse and addiction. This review provides a comprehensive overview of existing MR studies of adolescent alcohol and drug users. The most common alterations reported across substance used and MR modalities are in the frontal lobe (63% of published studies). This is not surprising, given that this is the last region to reach neurobiological adulthood. Comparatively, evidence is less consistent regarding alterations in regions that mature earlier (e.g., amygdala, hippocampus), however newer techniques now permit investigations beyond regional approaches that are uncovering network-level vulnerabilities. Regardless of whether neurobiological signatures exist prior to the initiation of use, this body of work provides important direction for ongoing prospective investigations of adolescent brain development, and the significant impact of alcohol and substance use on the brain during the second decade of life.