Cannabis Group Research Articles

Cannabis-induced alterations in brain activation during a test of information processing speed in patients with MS.

ObjectiveThe objective of this article is to determine the functional brain correlates of information processing speed in multiple sclerosis (MS) patients who smoke cannabis and those who are drug naïve.MethodsTwo neurologically and demographically matched samples of MS patients were enrolled, those who smoked cannabis daily (n = 20) and those who were cannabis naïve (n = 19). All participants completed the Brief Repeatable Battery of Neuropsychological Tests and underwent fMRI testing during which they were administered a modified version of the Symbol Digit Modalities Test (mSDMT).ResultsThe cannabis group responded slower in nine of 11 blocks of the mSDMT (p < 0.001), showing a trend toward a slower response time (p < 0.08), but did not differ in the accuracy of response (p < 0.18). Both groups displayed activation in a prefrontal cortex-parietal network associated with information processing speed. When compared to the cannabis-naïve group, cannabis users showed less activation in the right (p = 0.009) and left (p = 0.001) thalami and increased activation in the anterior cingulate (p = 0.006).ConclusionRegular cannabis use in MS patients is associated with slower information processing speed and a pattern of cerebral activity that differs from cannabis-naïve individuals, most notably in a bilateral reduction of thalamic activity.

Poorer frontolimbic white matter integrity is associated with chronic cannabis use, FAAH genotype, and increased depressive and apathy symptoms in adolescents and young adults.

BackgroundThe heaviest period of cannabis use coincides with ongoing white matter (WM) maturation. Further, cannabis-related changes may be moderated by FAAH genotype (rs324420). We examined the association between cannabis use and FAAH genotype on frontolimbic WM integrity in adolescents and emerging adults. We then tested whether observed WM abnormalities were linked with depressive or apathy symptoms.MethodsParticipants included 37 cannabis users and 37 healthy controls (33 female; ages 18–25). Multiple regressions examined the independent and interactive effects of variables on WM integrity.ResultsRegular cannabis users demonstrated reduced WM integrity in the bilateral uncinate fasciculus (UNC) (MD, right: p = .009 and left: p = .009; FA, right: p = .04 and left: p = .03) and forceps minor (fMinor) (MD, p = .03) compared to healthy controls. Marginally reduced WM integrity in the cannabis users was found in the left anterior thalamic radiation (ATR) (FA, p = .08). Cannabis group ∗ FAAH genotype interaction predicted WM integrity in bilateral ATR (FA, right: p = .05 and left: p = .001) and fMinor (FA, p = .02). In cannabis users, poorer WM integrity was correlated with increased symptoms of depression and apathy in bilateral ATR and UNC.ConclusionsConsistent with prior findings, cannabis use was associated with reduced frontolimbic WM integrity. WM integrity was also moderated by FAAH genotype, in that cannabis-using FAAH C/C carriers and A carrying controls had reduced WM integrity compared to control C/C carriers. Observed frontolimbic white matter abnormalities were linked with increased depressive and apathy symptoms in the cannabis users.

Methamphetamine and cannabis abuse in adolescence: a quasi-experimental study on specific and long-term neurocognitive effects

ObjectivesMethamphetamine abuse affects brain structure and function. Although methamphetamine and cannabis are commonly abused together, few studies have investigated the differential neurocognitive consequences of methamphetamine abuse with or without cannabis....

Impact of Cannabis Use on Long-Term Remission in Bipolar I and Schizoaffective Disorder.

ObjectiveTo investigate the impact of regular cannabis use on long-term remission of mood symptoms in bipolar spectrum disorders.MethodsThe 24-month prospective observational study included patients (n=239) with bipolar I disorder and schizoaffective disorder, bipolar type. Participants were classified as regular cannabis users (three times or more per week) or non-users. The primary outcome measure was the achievement of remission on the evaluations during the 24 months.ResultsOf the 234 participants for whom data was available, 25 (10.7%) were regular cannabis users, and the group comprised significantly more males than females. In the total population, cannabis use was significantly associated with decreased likelihood of remission during the 24-month follow-up period. Subgroup analyses showed that cannabis use was significantly associated with lower remission rates on the Hamilton Depression Rating Scale in females (n=139) and patients prescribed mood stabilizers alone (n=151), whereas in males (n=95) and patients prescribed olanzapine and/or a mood stabilizer (n=83), cannabis use was significantly associated with lower remission rates on the Young Mania Rating Scale. Remission rates were lowest in the concurrent cannabis and tobacco smoking group (n=22) followed by the tobacco smoking only group (n=97), and the non-smoker group (n=116). The post-hoc analysis revealed that all remission rates were significantly lower in the concurrent cannabis and the tobacco smoking group compared to the non-smoker group.ConclusionCannabis use negatively affects the long-term clinical outcome in patients with bipolar spectrum disorders. A comprehensive assessment and integrated management of cannabis use are required to achieve better treatment outcomes for bipolar spectrum disorders.

Motion Discrimination is Impaired in Cannabis Users.

Event Abstract Back to Event Motion Discrimination is Impaired in Cannabis Users. Elena Mikulskaya1* and Frances Martin1 1 University of Newcastle, School of Psychology, Australia Chronic cannabis use is associated with deficits in visual attention and perception, and reduced dopamine levels, especially with early-onset use. Motion perception is impaired with altered dopaminergic functioning in people with Schizophrenia and Parkinson's disease and in abstaining drug users. Such deficits in motion perception have been shown to be exacerbated at low contrast and in low luminance conditions. This study tested the hypothesis that early-onset cannabis users will show impaired motion perception under low light conditions compared to controls. Motion coherence thresholds were collected from 19 controls (11 male, mean age 22.4 years) and 14 cannabis users (8 male, mean age 23.6 years). Participants completed two discrimination of direction of motion (radial and translational) tasks at three luminance levels (69, 3 and 0.5cd/m2). In each task 50 dots were presented on the screen for 500msec, moving at 5.6 d/sec speed upward or downward in the translational task, and inward or outward in the radial task. The contrast of the dots was at 12 and 24% and varied pseudo-randomly across trials in each task. A two-alternative forced choice paradigm (direction discrimination: upward vs downward; inward vs outward) and a two-down, one-up staircase procedure were employed. The interaction between contrast and group (F1,31=5.6741, p=0.02) was significant. The groups did not differ at 12% contrast however at 24% contrast the coherence threshold was higher for the cannabis group than the controls. This effect was modified by a trend towards a significant interaction between motion type, contrast and group (F1,31=3.8643, p=0.058), which suggested that this effect was confined to the radial direction of motion. This is the first study showing that abstaining cannabis users present a specific deficit in processing of complex motion such as radial motion. These results suggest that cannabis users can be impaired in everyday tasks such as driving. Keywords: Visual Perception, Cannabis use, radial motion, Low contrast, motion coherence threshold Conference: XII International Conference on Cognitive Neuroscience (ICON-XII), Brisbane, Queensland, Australia, 27 Jul - 31 Jul, 2014. Presentation Type: Poster Topic: Sensation and Perception Citation: Mikulskaya E and Martin F (2015). Motion Discrimination is Impaired in Cannabis Users.. Conference Abstract: XII International Conference on Cognitive Neuroscience (ICON-XII). doi: 10.3389/conf.fnhum.2015.217.00254 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 19 Feb 2015; Published Online: 24 Apr 2015. * Correspondence: Ms. Elena Mikulskaya, University of Newcastle, School of Psychology, Ourimbah, Australia, c3176499@uon.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Elena Mikulskaya Frances Martin Google Elena Mikulskaya Frances Martin Google Scholar Elena Mikulskaya Frances Martin PubMed Elena Mikulskaya Frances Martin Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

PC-FACS

PC-FACS

Disrupted Gamma-Band Neural Oscillations During Coherent Motion Perception in Heavy Cannabis Users

Previous work in animals and humans has shown that exogenous cannabinoids disrupt time-locked, evoked gamma oscillations (30-80 Hz). However, no studies to date have examined the effect of cannabis on non-time-locked, induced gamma oscillations during more complex Gestalt perception. The current study therefore utilized electroencephalography (EEG) to examine gamma oscillations during coherent motion perception in heavy cannabis users and controls. Chronic cannabis users (n = 24; 12 h abstinence before study; positive 11-nor-9-carboxy-delta-9-tetrahydrocannabinol urine levels) and cannabis-naive controls (n = 23) were evaluated. Stimuli consisted of random dot kinetograms (RDKs) that subjects passively viewed during three different conditions: coherent motion, incoherent motion, and static. Time × frequency analysis on EEG data was performed using Fourier-based mean trial power (MTP). Transient event-related potentials (ERPs) to stimulus onset (visual N100 and P200 components) were also evaluated. The results showed that the coherent motion condition produced a robust increase in neural activity in the gamma range (induced power from 40 to 59 Hz) as compared with the incoherent motion and static conditions. As predicted, the cannabis group showed significant reductions in induced gamma power in the coherent condition relative to healthy controls. No differences were observed between the groups in the N100 or P200 components, indicating intact primary sensory processing. Finally, cannabis users showed a trend toward increased scores on the Chapman Perceptual Aberration Scale (PAS) that was positively correlated with total years of active cannabis use. These data suggest that cannabis use may interfere with the generation of induced gamma-band neural oscillations that could in part mediate the perceptual-altering effects of exogenous cannabinoids.

Effects of cannabis on cognition in patients with MS: a psychometric and MRI study.

To determine functional and structural neuroimaging correlates of cognitive dysfunction associated with cannabis use in multiple sclerosis (MS). In a cross-sectional study, 20 subjects with MS who smoked cannabis and 19 noncannabis users with MS, matched on demographic and neurologic variables, underwent fMRI while completing a test of working memory, the N-Back. Resting-state fMRI and structural MRI data (lesion and normal-appearing brain tissue volumes, diffusion tensor imaging metrics) were also collected. Neuropsychological data pertaining to verbal (Selective Reminding Test Revised) and visual (10/36 Spatial Recall Test) memory, information processing speed (Paced Auditory Serial Addition Test [2- and 3-second versions] and Symbol Digit Modalities Test), and attention (Word List Generation) were obtained. The cannabis group performed more poorly on the more demanding of the Paced Auditory Serial Addition Test tasks (i.e., 2-second version) (p < 0.02) and the 10/36 Spatial Recall Test (p < 0.03). Cannabis users had more diffuse cerebral activation across all N-Back trials and made more errors on the 2-Back task (p < 0.006), during which they displayed increased activation relative to nonusers in parietal (p < 0.007) and anterior cingulate (p < 0.001) regions implicated in working memory. No group differences in resting-state networks or structural MRI variables were found. Patients with MS who smoke cannabis are more cognitively impaired than nonusers. Cannabis further compromises cerebral compensatory mechanisms, already faulty in MS. These imaging data boost the construct validity of the neuropsychological findings and act as a cautionary note to cannabis users and prescribers.

N-acetyl Aspartate Levels in Adolescents With Bipolar and/or Cannabis Use Disorders

Objective: Bipolar and cannabis use disorders commonly co-occur during adolescence, and neurochemical studies may help clarify the pathophysiology underlying this co-occurrence. This study compared metabolite concentrations in the left ventral lateral prefrontal cortex among adolescents with bipolar disorder (bipolar group; n = 14), adolescents with a cannabis use disorder (cannabis use group; n = 13), adolescents with cannabis use and bipolar disorders (bipolar and cannabis group; n = 25), and healthy adolescents (healthy controls; n = 15). We hypothesized that adolescents with bipolar disorder (with or without cannabis use disorder) would have decreased N-acetyl aspartate levels in the ventral lateral prefrontal cortex compared to the other groups and that the bipolar and cannabis group would have the lowest N-acetyl aspartate levels of all groups. Methods: N-acetyl aspartate concentrations in the left ventral lateral prefrontal cortex were obtained using proton magnetic resonance spectroscopy. Results: Adolescents with bipolar disorder showed significantly lower left ventral lateral prefrontal cortex N-acetyl aspartate levels, but post hoc analyses indicated that this was primarily due to increased N-acetyl aspartate levels in the cannabis group. The cannabis use disorder group had significantly higher N-acetyl aspartate levels compared to the bipolar disorder and the bipolar and cannabis groups (p = .0002 and p = .0002, respectively). Pearson correlations revealed a significant positive correlation between amount of cannabis used and N-acetyl aspartate concentrations. Conclusions: Adolescents with cannabis use disorder showed higher levels of N-acetyl aspartate concentrations that were significantly positively associated with the amount of cannabis used; however, this finding was not present in adolescents with comorbid bipolar disorder.

Abnormal maximal finger tapping in abstinent cannabis users

To investigate movement speed and rhythmicity in abstinent cannabis users, we hypothesized that abstinent cannabis users exhibit decreased maximal finger tapping frequency and increased variability of tapping compared with non-drug users. The study involved 10 healthy adult cannabis users and 10 age-matched and gender-matched controls with no history of illicit drug use. Subjects underwent a series of screening tests prior to participation. Subjects were then asked to tap a strain gauge as fast as possible with the index finger of their dominant hand (duration 5 s). The average intertap interval did not significantly differ between groups, but the coefficient of variation of the intertap interval was significantly greater in the cannabis group than in controls (p=0.011). The cannabis group also exhibited a slow tapping frequency at the beginning of the task. Rhythmicity of finger tapping is abnormal in individuals with a history of cannabis use. The abnormality appears to be long lasting and adds to the list of functional changes present in abstinent cannabis users.

Cannabis Induces a Clinical Response in Patients With Crohn's Disease: A Prospective Placebo-Controlled Study

The marijuana plant Cannabis sativa has been reported to produce beneficial effects for patients with inflammatory bowel diseases, but this has not been investigated in controlled trials. We performed a prospective trial to determine whether cannabis can induce remission in patients with Crohn's disease. We studied 21 patients (mean age, 40 ± 14 y; 13 men) with Crohn's Disease Activity Index (CDAI) scores greater than 200 who did not respond to therapy with steroids, immunomodulators, or anti-tumor necrosis factor-α agents. Patients were assigned randomly to groups given cannabis, twice daily, in the form of cigarettes containing 115 mg of Δ9-tetrahydrocannabinol (THC) or placebo containing cannabis flowers from which the THC had been extracted. Disease activity and laboratory tests were assessed during 8 weeks of treatment and 2 weeks thereafter. Complete remission (CDAI score, <150) was achieved by 5 of 11 subjects in the cannabis group (45%) and 1 of 10 in the placebo group (10%; P = .43). A clinical response (decrease in CDAI score of >100) was observed in 10 of 11 subjects in the cannabis group (90%; from 330 ± 105 to 152 ± 109) and 4 of 10 in the placebo group (40%; from 373 ± 94 to 306 ± 143; P = .028). Three patients in the cannabis group were weaned from steroid dependency. Subjects receiving cannabis reported improved appetite and sleep, with no significant side effects. Although the primary end point of the study (induction of remission) was not achieved, a short course (8 weeks) of THC-rich cannabis produced significant clinical, steroid-free benefits to 10 of 11 patients with active Crohn's disease, compared with placebo, without side effects. Further studies, with larger patient groups and a nonsmoking mode of intake, are warranted. ClinicalTrials.gov, NCT01040910.

The Effects of Inhalant Misuse on Attentional Networks

Inhalant misuse among adolescents is poorly understood from a neuropsychological perspective. This study aimed to identify attentional deficits related to inhalant misuse measured with the Attention Network Test (ANT). We examined three groups: 19 inhalant users, 19 cannabis users, and 18 community controls. There were no group differences on the ANT measures of orienting, alerting, and executive control. However, compared to the cannabis and control groups, inhalant users demonstrated an increased rate of response errors in the absence of any reaction time differences. These differences may reflect a selective deficit in sustained attention or greater impulsivity in the inhalant group.

Cannabis Psychosis: Examining the Evidence for a Distinctive Psychopathology in a Systematic and Narrative Review

The term "cannabis psychosis" has become ubiquitous in the psychiatric literature. Few authors have described the precise psychopathology of this potentially distinct subtype of psychosis. Specifically, little attention has been paid to exploring whether cannabis psychosis is characterized by a psychopathology which is different from that of other types of psychosis. The purpose of this paper was to systematically review the literature for evidence of a specific constellation of symptoms which are consistently characteristic of cannabis psychosis within an inpatient psychiatric setting and to determine whether these combine to create a psychopathology which is distinct from that of other types of psychosis. Systematic review using Meta-analysis Of Observational Studies in Epidemiology (MOOSE) guidelines. 13 studies of the 439 identified met the inclusion criteria. Only eight studies had sufficient internal and external validity to allow comparison in a narrative format of the psychopathology present, compared with controls. Of these eight selected studies, seven reported at least one significant difference (p < .05) in the psychopathology of the cannabis group to the control group used as a comparator. This study should be interpreted with great caution and conclusions should not be generalized. These findings do not suggest that "cannabis psychosis" does not exist, only that from a psychopathological perspective it may not be qualitatively any different from other forms of psychosis. Future research in this area needs to focus on clarifying the definition or description of "cannabis psychosis" and the use of standardized robust experimental and/or observational designs to eliminate heterogeneity that may lead to inconclusive results.

The Effect of Chronic Cannabinoids on Broadband EEG Neural Oscillations in Humans

Animal and cellular work has shown that central cannabinoid-1 receptors modulate neural oscillations in the gamma range (40 Hz), which may be important for normal perceptual and cognitive processes. In order to assess the effect of cannabinoids on broadband-frequency neural oscillations in humans, the current study examined the effect of chronic cannabis use on auditory steady-state responses (ASSRs) utilizing electroencephalography (EEG). Passive ASSRs were assessed using varying rates of binaural stimulation (auditory click-trains; 10-50 Hz in increments of 5 Hz; 80 dB SPL) in carefully screened cannabis users and controls. Chronic cannabis users (n=22; 12 h abstinence before study; positive 11-nor-9-carboxy-delta-9-tetrahydrocannabinol urine levels) and cannabis naïve controls (n=24) were evaluated. Time X frequency analyses on EEG data were performed using Fourier-based mean trial power (MTP) and phase-locking (inter-trial coherence; ITC). Transient ERPs to stimulus onset (auditory N100 components) were also evaluated. As predicted, a decrease in spectral power (MTP) at 40 Hz was observed in the cannabis group (p<0.018). No effects on phase-locking (ITC) or the N100 were observed. Further, within the cannabis group, lower 40 Hz power correlated with an earlier age of onset of cannabis use (p<0.04). These data suggest that chronic exposure to exogenous cannabinoids can alter the ability to generate neural oscillations, particularly in the gamma range. This is consistent with preclinical animal and cellular data, which may have implications for understanding the short- and long-term psychopharmacological effects of cannabis.

Methamphetamine Use and Schizophrenia: A Population-Based Cohort Study in California

Clinical investigators in Japan have long suggested that exposure to methamphetamine might cause a persistent schizophrenia-like psychosis. This possibility is discounted in the Western literature. To investigate the relationship between drug use and later schizophrenia, the authors conducted a large-scale cohort study of drug users initially free of persistent psychosis. A population-based cohort study was conducted using data from California inpatient hospital discharge records from 1990 through 2000. Patients with methamphetamine-related conditions (N=42,412) and those with other drug use disorders (cannabis, cocaine, alcohol, and opioids) were propensity score-matched to individuals with primary appendicitis who served as a population proxy comparison group; the methamphetamine cohort was also matched to the other drug cohorts. Cox modeling was used to estimate differences between matched groups in the rates of subsequent admission with schizophrenia diagnoses. The methamphetamine cohort had a significantly higher risk of schizophrenia than the appendicitis group (hazard ratio=9.37) and the cocaine, opioid, and alcohol groups (hazard ratios ranging from 1.46 to 2.81), but not significantly different from that of the cannabis group. The risk of schizophrenia was higher in all drug cohorts than in the appendicitis group. Study limitations include difficulty in confirming schizophrenia diagnoses independent of drug intoxication and the possibility of undetected schizophrenia predating drug exposure. The study's findings suggest that individuals with methamphetamine-related disorders have a higher risk of schizophrenia than those with other drug use disorders, with the exception of cannabis use disorders. The elevated risk in methamphetamine users may be explained by shared etiological mechanisms involved in the development of schizophrenia.

Impulsivity differences in recreational cannabis users and binge drinkers in a university population

BackgroundRecreational cannabis use and alcohol binge drinking are the most common drug consumption patterns in young adults. Impulsivity and several psychopathological signs are increased in chronic drug users, but the implications of recreational use are still poorly understood. MethodsWe evaluated impulsivity, sensation-seeking traits, impulsive decision-making, inhibitory control and possible symptoms of depression, anxiety and psychosis in three groups of young university adults: recreational cannabis users (N=20), alcohol binge drinkers (N=22) and non-drug users (N=26). ResultsThe cannabis and binge drinking groups had increased scores for impulsivity and sensation-seeking traits. Both groups also exhibited increased impulsive decision-making on the two-choice task and the Iowa Gambling task; however, only the cannabis group was significantly different from the non-drug group regarding inhibitory control (Go/No-Go and Stop tasks). The cannabis and binge drinking groups did not show differences in the psychopathological symptoms evaluated. ConclusionsOur observations of this population of non-dependent drug users are consistent with the increased impulsivity traits and behaviors that have been described previously in chronic drug abusers. In this study, compared to no drug use, the recreational use of cannabis was associated with a major dysfunction of the different facets of impulsive behaviors. However, alcohol binge drinking was related only to impulsive decision-making. These results suggest that impulsivity traits and behaviors are present not only in chronic drug abusers but also in recreational drug users. Future work should continue to investigate the long-term effects of these common consumption patterns on various impulsive behaviors and psychopathological symptoms.

Substance-induced psychotic disorders: 13-Year data from a de-addiction centre and their clinical implications

The relationship between substance use and psychotic disorder has been complex. Alcohol, cannabis, amphetamines, hallucinogens, and phencyclidine have been implicated as a causative factor for psychotic disorders. It is important to differentiate substance induced psychotic disorders (SIPDs) from primary psychotic disorders as management of the two conditions is different. There is paucity of research in the area of SIPD particularly from Asia. The present study was a retrospective study and it determines retrospectively the incidence rate and clinical characteristics of the SIPDs over a period of 13 years. The incidence of SIPDs was found to be 1.4% and all the subjects were males. In the present study, only alcohol and cannabis were implicated as causative agents for SIPDs. The most common type of psychosis was schizophrenia like psychosis, being more common in the cannabis group. The other forms of psychosis included delusional type, hallucinatory type and affective psychosis. 20% of the subjects had a change in diagnosis to either schizophrenia or affective psychosis on follow-up. The present study showed that the presentation of SIPDs is similar to the primary psychotic disorder and this has management implication.

Use of cannabis and psychopathological risk in onset psychosis

The aim of the study is to assess the correlations between cannabis use and psychopathological features, disorder severity and global functioning in subjects with onset psychosis (schizophrenic and bipolar psychosis) and at risk mental state. Sixty-seven consecutive subjects with diagnosis of bipolar spectrum disorder (N=49), schizophrenic spectrum disorder (N=5) and at risk mental state (N=13) were recruited from the SMILE (Service for Monitoring and early Intervention Looking at the fight against the onset of mental Even psychological youths' suffering). All subjects were assessed with the Self Report Symptom Inventory-90 (SCL-90), the Global Assessment of Functioning scale (GAF) and Clinical Global Impressions-Severity (CGI-S). Moreover, they were assessed for the cannabis use in the last month. The total sample was splitted in two groups: Group 1 of cannabis use subjects (N=30) and Group 2 of no cannabis use subjects (N=37). Group 1 subjects showed significant higher scores at psychoticism SCL-90 dimension and at CGI-S than Group 2 subjects. The higher scores at anger/hostility and psychoticism SCL-90 dimensions and at CGI-S seem to be discriminant features of Group 1 cannabis use subjects. The data reported suggest that cannabis use assessment in onset psychosis (bipolar and schizophrenic onset) and at risk mental state could add clinical information to the psychopathological and diagnostic description. Such information should be ''incorporated'' in the treatment choice model and outcome prediction assessment.

Influence of Cannabis on Fatal Traffic Crashes

The influence of cannabis on traffic crashes is a growing concern. Experimental studies provide ample evidence of cannabis influence on psychomotor and cognitive performances. Epidemiological works describe the excess crash risk that this substance causes. Yet this psychotropic drug's influence in causing crashes is still at the center of many discussions. The present analysis exploits crash data in detail to obtain a more precise understanding of the failures that drivers are subject to when they have consumed cannabis, depending on the level of tetrahydrocannabinol (THC) measured in blood samples. Two groups representative of fatal crashes in France were studied: a cannabis group (n = 174) and a control group (n = 174) involving use of neither cannabis nor alcohol. Results of this analysis notably showed that cannabis consumption significantly increased the rate of generalized failures by the driver, reflecting an alteration of all sensorial, motor, and cognitive functions, specifically for high blood levels of THC (&gt;5 ng/mL). At lower levels of intoxication, cannabis leads to a poor diagnosis of driving difficulties.

An fMRI Study of Neuronal Activation in Schizophrenia Patients with and without Previous Cannabis Use

Previous studies have mostly shown positive effects of cannabis use on cognition in patients with schizophrenia, which could reflect lower neurocognitive vulnerability. There are however no studies comparing whether such cognitive differences have neuronal correlates. Thus, the aim of the present study was to compare whether patients with previous cannabis use differ in brain activation from patients who has never used cannabis. The patients groups were compared on the ability to up-regulate an effort mode network during a cognitive task and down-regulate activation in the same network during a task-absent condition. Task-present and task-absent brain activation was measured by functional magnetic resonance neuroimaging (fMRI). Twenty-six patients with a DSM-IV and ICD-10 diagnosis of schizophrenia were grouped into a previous cannabis user group and a no-cannabis group. An auditory dichotic listening task with instructions of attention focus on either the right or left ear stimulus was used to tap verbal processing, attention, and cognitive control, calculated as an aggregate score. When comparing the two groups, there were remaining activations in the task-present condition for the cannabis group, not seen in the no-cannabis group, while there was remaining activation in the task-absent condition for the no-cannabis group, not seen in the cannabis group. Thus, the patients with previous cannabis use showed increased activation in an effort mode network and decreased activation in the default mode network as compared to the no-cannabis group. It is concluded that the present study show some differences in brain activation to a cognitively challenging task between previous cannabis and no-cannabis schizophrenia patients.