Altered cortical maturation in adolescent cannabis users with and without schizophrenia

Transcriptional patterns of the cortical Morphometric Inverse Divergence in first-episode, treatment-naïve early-onset schizophrenia

Early-onset Schizophrenia (EOS) is a profoundly progressive psychiatric disorder characterized by both positive and negative symptoms, whose pathogenesis is influenced by genes, environment and brain structure development. In this study, the MIND (Morphometric Inverse Divergence) network was employed to explore the relationship between morphological similarity and specific transcriptional expression patterns in EOS patients. This study involved a cohort of 187 participants aged between 7 and 17 years, consisting of 97 EOS patients and 90 healthy controls (HC). Multiple morphological features were used to construct the MIND network for all participants. Furthermore, we explored the associations between MIND network and brain-wide gene expression in EOS patients through partial least squares (PLS) regression, shared genetic predispositions with other psychiatric disorders, functional enrichment of PLS weighted genes, as well as transcriptional signature assessment of cell types, cortical layers, and developmental stages. The MIND showed similarity differences in the orbitofrontal cortex, pericalcarine cortex, lingual gyrus, and multiple networks in EOS patients compared to HC. Moreover, our exploration revealed a significant overlap of PLS2 weighted genes linking to EOS-related MIND differences and the dysregulated genes reported in other psychiatric diseases. Interestingly, genes correlated with MIND changes (PLS2-) exhibited a significant enrichment not only in metabolism-related pathways, but also in specific astrocytes, cortical layers (specifically layer I and III), and posterior developmental stages (late infancy to young adulthood stages). However, PLS2+ genes were primarily enriched in synapses signaling-related pathways and early developmental stages (from early-mid fetal to neonatal early infancy) but not in special cell types or layers. These findings provide a novel perspective on the intricate relationship between macroscopic morphometric structural abnormalities and microscopic transcriptional patterns during the onset and progression of EOS.

Impact of Adolescent Cannabis Use on Neurocognitive and Brain Development

Research examining associations between frequent cannabis use in adolescence and brain-behavior outcomes has increased substantially over the past 2 decades. This review attempts to synthesize the state of evidence in this area of research while acknowledging challenges in interpretation. Although there is converging evidence that ongoing, frequent cannabis use in adolescence is associated with small reductions in cognitive functioning, there is still significant debate regarding the persistence of reductions after a period of abstinence. Similarly, there is controversy regarding the replicability of structural and functional neuroimaging findings related to frequent cannabis use in adolescence. Larger studies with informative designs are needed.

Impact of Adolescent Cannabis Use on Neurocognitive and Brain Development

Research examining associations between frequent cannabis use in adolescence and brain-behavior outcomes has increased substantially over the past 2 decades. This review attempts to synthesize the state of evidence in this area of research while acknowledging challenges in interpretation. Although there is converging evidence that ongoing, frequent cannabis use in adolescence is associated with small reductions in cognitive functioning, there is still significant debate regarding the persistence of reductions after a period of abstinence. Similarly, there is controversy regarding the replicability of structural and functional neuroimaging findings related to frequent cannabis use in adolescence. Larger studies with informative designs are needed.

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.

Abnormal Brain Structure Morphology in Early-Onset Schizophrenia

With less exposure to environmental and medication influences, individuals with early-onset schizophrenia (EOS) may provide valuable evidence to study the pathogenesis and phenotypic pattern of schizophrenia.T1-weighted magnetic resonance images were collected in 60 individuals with EOS and 40 healthy controls. Voxel-based morphometry and surface-based morphometry analyzes were performed. Gray matter volume, cortical thickness and cortical surface area were compared between the EOS and healthy controls and among schizophrenia subgroups (with or without family history of schizophrenia). Compared with healthy controls, the EOS group had reduced gray matter volume in the bilateral middle temporal gyrus and reduced cortical thickness in several brain regions. The sporadic early onset schizophrenia and the familial early onset schizophrenia showed different brain structure morphology. These findings suggest that abnormal brain structure morphology, especially in the temporal and frontal lobes, may be an important pathophysiological feature of EOS.

The Effects of Alcohol and Cannabis Co-Use on Neurocognitive Function, Brain Structure, and Brain Function

Purpose of review

Given increases in the rates of alcohol and cannabis co-use among adolescents and young adults, this review aims to summarize literature on the effects of alcohol and cannabis co-use on neurocognitive functioning, brain structure, and brain function.

Recent findings

The limited existing studies examining concurrent, recent, and lifetime alcohol and cannabis co-use suggest effects on the brain are likely multifaceted. The majority of studies report that co-use is associated with negative outcomes such as impaired cognitive function and significant alterations in key structural and functional regions of the brain, while others report null effects of co-use compared to non-substance using control and single-substance use groups.

Summary

Current studies lack a general consensus on methodology, definitions of concurrent and simultaneous use, and neuroimaging approaches, which makes it challenging to draw strong conclusions about the effects of co-use. More studies are needed to explore the effects of co-use in the context of simultaneous alcohol and cannabis use.

Individuals at increased risk for development of bipolar disorder display structural alterations similar to people with manifest disease

In psychiatry, there has been a growing focus on identifying at-risk populations. For schizophrenia, these efforts have led to the development of early recognition and intervention measures. Despite a similar disease burden, the populations at risk of bipolar disorder have not been sufficiently characterized. Within the BipoLife consortium, we used magnetic resonance imaging (MRI) data from a multicenter study to assess structural gray matter alterations in N = 263 help-seeking individuals from seven study sites. We defined the risk using the EPIbipolar assessment tool as no-risk, low-risk, and high-risk and used a region-of-interest approach (ROI) based on the results of two large-scale multicenter studies of bipolar disorder by the ENIGMA working group. We detected significant differences in the thickness of the left pars opercularis (Cohen's d = 0.47, p = 0.024) between groups. The cortex was significantly thinner in high-risk individuals compared to those in the no-risk group (p = 0.011). We detected no differences in the hippocampal volume. Exploratory analyses revealed no significant differences in other cortical or subcortical regions. The thinner cortex in help-seeking individuals at risk of bipolar disorder is in line with previous findings in patients with the established disorder and corresponds to the region of the highest effect size in the ENIGMA study of cortical alterations. Structural alterations in prefrontal cortex might be a trait marker of bipolar risk. This is the largest structural MRI study of help-seeking individuals at increased risk of bipolar disorder.

Cannabis use and hippocampal subfield volumes in males with a first episode of a schizophrenia spectrum disorder and healthy controls

BACKGROUND

Both schizophrenia and cannabis use are associated with structural brain changes. The hippocampus is a region of particular interest due to its role in memory and select cognitive functions, impairment of which is a core feature of schizophrenia and has also been observed in substance abuse. This study aimed to explore the effects of recent/current cannabis use on hippocampal subfield volumes in male patients with first-episode schizophrenia spectrum disorders and matched controls.

METHODS

This cross-sectional, case-control study included 63 patients and 58 controls scanned on 3T MRI scanners, with hippocampal segmentation performed using recently validated Freesurfer v6.0 software. Cannabis use status was determined by self and carer report together with urine toxicology screening, and patients were categorised as recent/current users or non-users. We used multivariate analysis of covariance (MANCOVA) with age, scan sequence, scan quality, and total intracranial volume as covariates, with subsequent analysis of variance (ANOVA) to test the effects of diagnosis and cannabis use status on individual hippocampal subfields.

RESULTS

We found a group (patient/control) by cannabis use interaction effect in the subiculum, with decreased volumes observed in the cannabis non-using patients compared to the cannabis using patients, and decreased volumes in the cannabis using controls compared to the cannabis non-using controls.

CONCLUSION

The increased subiculum volume in cannabis using patients compared to cannabis non-using patients raises important questions regarding the pathophysiology of schizophrenia and the role of cannabis use therein.

Legalization of cannabis use in Canada: Impacts on the cannabis use profiles of youth seeking services for substance use

BACKGROUND

Cannabis is a highly used substance among youth, but has the potential to negatively impact the developing brain. Recreational cannabis use was legalized in Canada in October 2018. This exploratory study examines cannabis use profiles of high-risk youth before and after the national legalization of recreational cannabis use.

METHOD

This cross-sectional cohort study examines the cannabis use profiles of two cohorts of youth, one recruited prior to legalization (N = 101) and one recruited after legalization (N = 168).

RESULTS

This study found few changes in cannabis use patterns after legalization. The rate of high-frequency cannabis use, polysubstance use, social circles of use, and mental health and substance use challenges showed no change, and the study found no associations with age. Exceptions were that youth were more likely to report purchasing cannabis from a legal source after legalization. Concealment of cannabis use from legal authorities declined after legalization among youth over the age of majority (19+ years), but not among younger youth (<19 years).

CONCLUSIONS

Minimal changes have occurred in the cannabis use patterns of service-seeking youth in the short term following legalization. This holds true both for youth who have reached the age of majority and those who have not. Nevertheless, this population has overlapping substantial mental health and substance use challenges. Integrated services should address cannabis use and other concurrent challenges and be sensitive to the postlegalization social climate.

Age- and Sex-Related Cortical Gray Matter Volume Differences in Adolescent Cannabis Users: A Systematic Review and Meta-Analysis of Voxel-Based Morphometry Studies

Introduction: Adolescent-onset cannabis use is rising in the era of marijuana legalization. Recent imaging studies have identified neuroanatomical differences between adult cannabis users and controls that are more prominent in early-onset users. Other studies point to sex-dependent effects of cannabis. Methods: A systematic review following PRISMA guidelines and subsequent effect-size seed-based d mapping (SDM) meta-analyses were conducted to investigate relationships between age (across the 12-to-21-year-old developmental window), sex, and gray matter volume (GMV) differences between cannabis using (CU) and typically developing (TD) youth. Results: Our search identified 1,326 citations, 24 of which were included in a qualitative analysis. A total of 6 whole-brain voxel-based morphometry (VBM) studies comparing regional GMV between 357 CU [mean (SD) age = 16.68 (1.28); 71% male] and 404 TD [mean (SD) age = 16.77 (1.36); 63% male] youth were included in the SDM-meta-analysis. Meta-analysis of whole-brain VBM studies identified no regions showing significant GMV difference between CU and TD youth. Meta-regressions showed divergent effects of age and sex on cortical GMV differences in CU vs. TD youth. Age effects were seen in the superior temporal gyrus (STG), with older-aged CU youth showing decreased and younger-aged CU youth showing increased STG GMV compared to age-matched TD youth. Parallel findings in the STG were also observed in relation to duration of CU (years) in supplemental meta-regressions. Regarding sex effects, a higher proportion of females in studies was associated with increased GMV in the middle occipital gyrus in CU vs. TD youth. Conclusions: These findings suggest that GMV differences between CU and TD youth, if present, are subtle, and may vary as a function of age, cumulative cannabis exposure, and sex in young people. Whether age- and sex-related GMV differences are attributable to common predispositional factors, cannabis-induced neuroadaptive changes, or both warrant further investigation.

Cognition and Cortical Thickness in Heavy Cannabis Users

INTRODUCTION

Acute and long-term adverse effects of heavy cannabis use (HCU) on neurocognitive function have been suggested, as much as regional changes of brain volume. However, little is known about the relationship between impaired cognition and brain structure in individuals with HCU.

OBJECTIVE

Here, we investigated associations between cognition and cortical thickness (CT) in males with HCU and male controls.

METHODS

Twenty-six individuals with HCU and 20 controls were examined using a comprehensive neuropsychological test battery and high-resolution structural MRI at 3T. CT was calculated using the Computational Anatomy Toolbox (CAT12).

RESULTS

Individuals with HCU differed from controls with respect to verbal learning performance and verbal working memory only. Individuals with HCU showed reduced CT in medial temporal, orbitofrontal, and cingulate regions, as well as in areas of the middle temporal and fusiform cortex (peak voxel family-wise error-corrected p < 0.001, followed by empirically determined correction for spatial extent) compared to HC. Verbal learning performance was associated with right entorhinal and left orbitofrontal CT reductions. Entorhinal CT was also significantly associated with amount and frequency of current weekly cannabis use.

CONCLUSIONS

The data support the notion of domain-specific cognitive impairment in individuals with HCU and provide a neuromechanistic understanding of such deficits, particularly with respect to abnormal CT in brain areas associated with long-term memory processing.

Neural and behavioral correlates associated with adolescent marijuana use

Purpose of Review

Marijuana (MJ) is one of the most commonly used drugs among adolescents. Exposure to MJ during adolescence can lead to alterations in brain development, and, subsequently to the behavioral correlates regulated by the affected brain regions. In this review, we discuss findings from preclinical and human studies examining the relationship between adolescent MJ use and the neurobiological and behavioral correlates associated with it.

Recent Findings

Current findings indicate that adolescent MJ use is associated with alterations in brain structure and function, especially in regions that express high levels of the cannabinoid 1 receptor such as the prefrontal cortex, hippocampus, cerebellum and limbic regions. These alterations are correlated with changes in affective, cognitive and reward-seeking behavior. Furthermore, evidence suggests that exposure to MJ during adolescence can have long-lasting and pronounced neural and behavioral effects into adulthood.

Summary

The wide ranging neural and behavioral correlates associated with MJ use during adolescence highlight the need for further studies to better understand the potential risk factors and/or neurotoxic effects of adolescent MJ use.

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.

Impact of At Least 2 Years of Synthetic Cannabinoid Use on Cognitive and Psychomotor Functions Among Treatment-Seeking Male Outpatients

Introduction: Synthetic cannabinoid (SC) use, an important public health problem, is becoming increasingly widespread and leads to many medical and psychiatric problems. This study aimed to evaluate the impact of SC use on cognitive and psychomotor functions of patients. Materials and Methods: The participants (30 outpatients with SC use disorder and 33 healthy controls) were administered the Montreal Cognitive Assessment (MOCA) test, the Edinburgh Handedness Inventory (EHI), the Finger-Tapping Test (FTT), and the Adult Memory and Information Processing Battery-B form (AMIPB-B). Results: The SC users scored lower in AMIPB-B, MOCA. and FTT compared to the healthy controls. Conclusion: These findings suggest that SC might impair both cognitive and psychomotor functions. Therefore, outpatients with SC use disorder should be carefully evaluated for cognitive and psychomotor functions since neurological examinations and interventions may also be required in treatment programs for these cases.

Cannabis and Pain Treatment-A Review of the Clinical Utility and a Practical Approach in Light of Uncertainty

Over the past decade the phenomenon of cannabis as a legitimate form of treatment for pain has overwhelmed the medical community, especially in the field of pain. From a status of a schedule 1 substance having no currently accepted medical use and being considered to have high potential for abuse, its use has mushroomed to over 50,000 legal medical users per year in Israel alone. There appear to be many reasons behind this phenomenon-medical, sociological, and economical. Thus, what is cannabis? An abusive substance or a medication? Should it be incorporated into current biomedical practice, and how should it be administered? Finally, what is the evidence for the beneficial and detrimental effects of cannabis? This article reviews and discusses the current literature regarding the beneficial and the detrimental effects of medical cannabis in the treatment of pain. We further discuss the problems and challenges facing the medical community in this domain and offer a practical approach to deal with these challenges.

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).

The Neuroscience of Drug Reward and Addiction

Drug consumption is driven by a drug's pharmacological effects, which are experienced as rewarding, and is influenced by genetic, developmental, and psychosocial factors that mediate drug accessibility, norms, and social support systems or lack thereof. The reinforcing effects of drugs mostly depend on dopamine signaling in the nucleus accumbens, and chronic drug exposure triggers glutamatergic-mediated neuroadaptations in dopamine striato-thalamo-cortical (predominantly in prefrontal cortical regions including orbitofrontal cortex and anterior cingulate cortex) and limbic pathways (amygdala and hippocampus) that, in vulnerable individuals, can result in addiction. In parallel, changes in the extended amygdala result in negative emotional states that perpetuate drug taking as an attempt to temporarily alleviate them. Counterintuitively, in the addicted person, the actual drug consumption is associated with an attenuated dopamine increase in brain reward regions, which might contribute to drug-taking behavior to compensate for the difference between the magnitude of the expected reward triggered by the conditioning to drug cues and the actual experience of it. Combined, these effects result in an enhanced motivation to "seek the drug" (energized by dopamine increases triggered by drug cues) and an impaired prefrontal top-down self-regulation that favors compulsive drug-taking against the backdrop of negative emotionality and an enhanced interoceptive awareness of "drug hunger." Treatment interventions intended to reverse these neuroadaptations show promise as therapeutic approaches for addiction.

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.

Are cannabis-using and non-using patients different groups? Towards understanding the neurobiology of cannabis use in psychotic disorders

A substantial body of credible evidence has accumulated that suggest that cannabis use is an important potentially preventable risk factor for the development of psychotic illness and its worse prognosis following the onset of psychosis. Here we summarize the relevant evidence to argue that the time has come to investigate the neurobiological effects of cannabis in patients with psychotic disorders. In the first section we summarize evidence from longitudinal studies that controlled for a range of potential confounders of the association of cannabis use with increased risk of developing psychotic disorders, increased risk of hospitalization, frequent and longer hospital stays, and failure of treatment with medications for psychosis in those with established illness. Although some evidence has emerged that cannabis-using and non-using patients with psychotic disorders may have distinct patterns of neurocognitive and neurodevelopmental impairments, the biological underpinnings of the effects of cannabis remain to be fully elucidated. In the second and third sections we undertake a systematic review of 70 studies, including over 3000 patients with psychotic disorders or at increased risk of psychotic disorder, in order to delineate potential neurobiological and neurochemical mechanisms that may underlie the effects of cannabis in psychotic disorders and suggest avenues for future research.

Evidence that reduced gray matter volume in psychotic disorder is associated with exposure to environmental risk factors

The aim of this study was to examine whether cannabis use, childhood trauma and urban upbringing are associated with total gray matter volume (GMV) in individuals with (risk for) psychotic disorder and whether this is sex-specific. T1-weighted MRI scans were acquired from 89 patients with a psychotic disorder, 95 healthy siblings of patients with psychotic disorder and 87 controls. Multilevel random regression analyses were used to examine main effects and interactions between group, sex and environmental factors in models of GMV. The three-way interaction between group, sex and cannabis (χ² =12.43, p<0.01), as well as developmental urbanicity (χ² = 6.29, p = 0.01) were significant, indicating that cannabis use and developmental urbanicity were associated with lower GMV in the male patient group (cannabis: B= -32.54, p < 0.01; developmental urbanicity: B= -10.23, p=0.03). For childhood trauma, the two-way interaction with group was significant (χ² = 5.74, p = 0.02), indicating that childhood trauma was associated with reduced GMV in the patient group (B=-9.79, p=0.01). The findings suggest that reduction of GMV in psychotic disorder may be the outcome of differential sensitivity to environmental risks, particularly in male patients.

Longitudinal changes in cognition in young adult cannabis users

INTRODUCTION

Adolescent cannabis use (CU) is associated with impaired attention, executive function, and verbal learning/memory. These associations are generally observed in cross-sectional studies. Longitudinal studies of cannabis users are lacking.

METHOD

The present study examines associations between CU and cognition over time in chronic daily adolescent-onset CUs, as compared to nonusing controls. Both groups completed a neuropsychological battery at study intake and again 2 years later.

RESULTS

Baseline group differences have been published and indicated deficits in verbal learning and memory, motivated decision-making, planning, and working memory in CUs. In this follow-up report, the longitudinal performance of users is compared to that of sustained nonusers using the same battery. At follow-up, the majority of CUs continued to report regular and heavy cannabis use. Relative impairments in the domains of working memory, planning and verbal memory remained stable, suggesting that these are enduring vulnerabilities associated with continued CU during young adulthood. Improvements in motivated decision-making were evident in both groups. In addition, CUs demonstrated relatively better performance on short-duration speeded tasks. An earlier age of CU onset was associated with poorer verbal learning and memory and planning performance over time.

CONCLUSIONS

Verbal learning and memory and planning processes, as well as their neural correlates, merit further scrutiny within etiological models of cannabis-induced cognitive impairments.

Heavy cannabis use prior psychosis in schizophrenia: clinical, cognitive and neurological evidences for a new endophenotype?

Cannabis use is associated with an increased risk of schizophrenia, and is considered to impact late neurodevelopment. Neurological soft signs (NSS) associated with schizophrenia are considered as markers of early neurodevelopmental impairment. Our study examines the association between heavy cannabis use before the onset of psychosis and clinical, neuropsychological and neurological symptoms, including NSS. In a cross-sectional study, we consecutively included 61 patients with schizophrenia (34 reporting heavy cannabis use before the onset of psychosis and 27 not reporting such use), in the setting of a University Hospital and a Medical Center. Symptoms assessment and substance use disorder were evaluated with the Diagnostic Interview for Genetic Studies. NSS were assessed with the Neurological Evaluation Scale. Psychopathology was assessed with the Positive and Negative Symptom Scale. All patients underwent a battery of neurocognitive tests evaluating attention, memory and executive functions domains. Patients with heavy cannabis use before the onset of psychosis showed significantly less NSS (p < 0.05), less negative symptoms (p < 10^-3) and a better cognitive functioning in different domains [median reaction time (p = 0.03), episodic memory (p = 0.04), visuoconstructive praxs (p = 0.03) than their non-heavy user counterparts]. Confounding effects of alcohol and tobacco were taken into account. Age and gender were not statistically different between the two groups (p = 0.70 and p = 0.16, respectively). Our study supports the clinical, neuropsychological and neurological specificity associated with the heavy use of cannabis before the onset of schizophrenia. Patients with heavy cannabis use before the onset of schizophrenia may exhibit later neurodevelopmental impairment than those who do not report such use. Schizophrenia associated with heavy cannabis use could represent a specific phenotype.

Co-use of Alcohol and Cannabis: A Review

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of the existing literature on the relationship between the co-use of cannabis and alcohol including (1) epidemiology, comorbidity, and associated consequences of cannabis and alcohol use disorders; (2) preclinical and clinical laboratory studies examining behavioral pharmacology of cannabis and alcohol co-use; and (3) clinical outcomes related to co-use.

RECENT FINDINGS

Findings from the literature reviewed suggest that the co-use of alcohol and cannabis is associated with additive performance impairment effects, higher and more frequent consumption levels, increased social and behavioral consequences such as driving while impaired, and greater likelihood of the experiencing comorbid substance use and mental health disorders. Furthermore, co-use may be associated with worse clinical outcomes, yet there are few studies examining the development and evaluation of interventions on reducing the co-use of cannabis and alcohol.

SUMMARY

There is a need for more rigorous and longitudinal research studies on the co-use of cannabis and alcohol to glean a more complete understanding of the relationship between the two substances. Findings can be used to develop and refine intervention strategies to successfully reduce cannabis and alcohol co-use.

Marijuana on the Mind? The Impact of Marijuana on Cognition, Brain Structure, and Brain Function, and Related Public Policy Implications

Although marijuana (MJ) has been used for thousands of years, the public’s opinion of MJ has shifted drastically over the past century, leaving many wondering about its potential risks and benefits. This article summarizes research detailing the impact of recreational MJ and related variables (frequency, magnitude, potency, and mode of MJ use) on cognition, brain structure, and brain function. MJ use, particularly at young ages, has been reported to undermine cognition, as well as alter brain structure and function. Furthermore, we discuss how data from recreational MJ studies, as well as more recent medical marijuana (MMJ) research findings, relate to legalization efforts. Considerations for policymakers, such as age limits, guidelines for safe use, and the therapeutic potential of certain constituents of MJ (i.e., cannabidiol), are also outlined. In recent years, policy has outpaced science; important areas in need of further research are noted.

Adolescent cortical thickness pre- and post marijuana and alcohol initiation

Cortical thickness abnormalities have been identified in youth using both alcohol and marijuana. However, limited studies have followed individuals pre- and post initiation of alcohol and marijuana use to help identify to what extent discrepancies in structural brain integrity are pre-existing or substance-related. Adolescents (N=69) were followed from ages 13 (pre-initiation of substance use, baseline) to ages 19 (post-initiation, follow-up). Three subgroups were identified, participants that initiated alcohol use (ALC, n=23, >20 alcohol use episodes), those that initiated both alcohol and marijuana use (ALC+MJ, n=23, >50 marijuana use episodes) and individuals that did not initiate either substance regularly by follow-up (CON, n=23, <3 alcohol use episodes, no marijuana use episodes). All adolescents underwent neurocognitive testing, neuroimaging, and substance use and mental health interviews. Significant group by time interactions and main effects on cortical thickness estimates were identified for 18 cortical regions spanning the left and right hemisphere (ps<0.05). The vast majority of findings suggest a more substantial decrease, or within-subjects effect, in cortical thickness by follow-up for individuals who have not initiated regular substance use or alcohol use only by age 19; modest between-group differences were identified at baseline in several cortical regions (ALC and CON>ALC+MJ). Minimal neurocognitive differences were observed in this sample. Findings suggest pre-existing neural differences prior to marijuana use may contribute to initiation of use and observed neural outcomes. Marijuana use may also interfere with thinning trajectories that contribute to morphological differences in young adulthood that are often observed in cross-sectional studies of heavy marijuana users.

Effects of Marijuana Use on Brain Structure and Function: Neuroimaging Findings from a Neurodevelopmental Perspective

Marijuana, behind only tobacco and alcohol, is the most popular recreational drug in America with prevalence rates of use rising over the past decade. A wide range of research has highlighted neurocognitive deficits associated with marijuana use, particularly when initiated during childhood or adolescence. Neuroimaging, describing alterations to brain structure and function, has begun to provide a picture of possible mechanisms associated with the deleterious effects of marijuana use. This chapter provides a neurodevelopmental framework from which recent data on brain structural and functional abnormalities associated with marijuana use is reviewed. Based on the current data, we provide aims for future studies to more clearly delineate the effects of marijuana on the developing brain and to define underlying mechanisms of the potential long-term negative consequences of marijuana use.

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.

Cannabis and Psychosis: a Critical Overview of the Relationship

Interest in the relationship between cannabis use and psychosis has increased dramatically in recent years, in part because of concerns related to the growing availability of cannabis and potential risks to health and human functioning. There now exists a plethora of scientific articles addressing this issue, but few provide a clear verdict about the causal nature of the cannabis-psychosis association. Here, we review recent research reports on cannabis and psychosis, giving particular attention to how each report provides evidence relating to two hypotheses: (1) cannabis as a contributing cause and (2) shared vulnerability. Two primary kinds of data are brought to bear on this issue: studies done with schizophrenic patients and studies of first-episode psychosis. Evidence reviewed here suggests that cannabis does not in itself cause a psychosis disorder. Rather, the evidence leads us to conclude that both early use and heavy use of cannabis are more likely in individuals with a vulnerability to psychosis. The role of early and heavy cannabis use as a prodromal sign merits further examination, along with a variety of other problem behaviors (e.g., early or heavy use of cigarettes or alcohol and poor school performance). Future research studies that focus exclusively on the cannabis-psychosis association will therefore be of little value in our quest to better understand psychosis and how and why it occurs.

Evaluating the impact of cannabis use on thalamic connectivity in youth at clinical high risk of psychosis

BACKGROUND

Disruptions in thalamic functional connectivity have been observed in people with schizophrenia and in youth at clinical high risk (CHR) of psychosis. However, the impact of environmental risk factors for psychosis on thalamic dysconnectivity is poorly understood. We tested whether thalamic dysconnectivity is related to patterns of cannabis use in a CHR sample.

METHODS

162 CHR and 105 control participants were assessed on cannabis use severity, frequency, and age at onset of first use as part of the North American Prodrome Longitudinal Study and completed resting-state fMRI scans. Whole-brain thalamic functional connectivity maps were generated using individual subjects' anatomically defined thalamic seeds.

RESULTS

Thalamic connectivity did not significantly correlate with current cannabis use severity or frequency in either CHR or controls. In CHR cannabis users, a significant correlation emerged between attenuated thalamic connectivity with left sensory/motor cortex and a younger age at onset of cannabis use. CHR who used cannabis before age 15 did not differ on thalamic connectivity as compared to CHR who used after age 15 or CHR who were cannabis naïve. No group differences in thalamic connectivity emerged when comparing CHR separated by moderate/high use frequency, low-frequency or cannabis naïve.

CONCLUSIONS

Although a younger age at onset of cannabis use may be associated with disrupted thalamo-cortical coupling, cannabis use does not appear to be an identifying characteristic for thalamic connectivity in CHR with moderate/high use frequency compared to low-frequency users or CHR who are cannabis naïve.

Cortical thinness and volume differences associated with marijuana abuse in emerging adults

BACKGROUND

The prevalence of marijuana (MJ) use among youth and its legalization for medical or recreational use has intensified public health endeavors of understanding MJ effects on brain structure and function. Studies indicate that MJ use is related to impaired cognitive performance, and altered functional brain activation and chemistry in adolescents and adults, but MJ effects on brain morphology in emerging adults are less understood.

METHODS

Fifteen MJ users (age 21.8±3.6, 2 females) and 15 non-user (NU) participants (age 22.3±3.5, 2 females) were included, demographically matched on age, education and alcohol use. High-resolution structural MR images were acquired at 3Tesla. Cortical thickness (CT) and volumetric analyses were performed using Freesurfer. A priori regions of interest (ROI) included orbitofrontal and cingulate cortices, amygdala, hippocampus and thalamus.

RESULTS

Whole brain CT analysis did not result in significant group differences in a priori ROIs but revealed MJ users had significantly less CT (i.e., thinness) in right fusiform gyrus (rFG) compared to NU (p<0.05). Thalamic volume was significantly smaller in MJ users compared to NU (right, p=0.05; left, p=0.01) and associated with greater non-planning (p<0.01) and overall impulsivity (p=0.04). There were no other group differences.

CONCLUSIONS

RFG cortical thinness and smaller thalamic volume in emerging adults is associated with MJ abuse. Furthermore, smaller thalamic volume associated with greater impulsivity contributes to growing evidence that the thalamus is neurobiologically perturbed by MJ use. Collectively, altered thalamic and rFG structural integrity may interfere with their known roles in regulating visuoperceptual and object information processing.