Heavy Cannabis Research Articles

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.

High impulsivity correlates with cannabis cue-induced craving in a non-treatment seeking cohort of heavy cannabis users

High impulsivity correlates with cannabis cue-induced craving in a non-treatment seeking cohort of heavy cannabis users

Peer Network Counseling as Brief Treatment for Urban Adolescent Heavy Cannabis Users.

A small body of evidence supports targeting adolescents who are heavy users of cannabis with brief interventions, yet more research is needed to confirm the effectiveness of these studies. We conducted a secondary analysis of our Peer Network Counseling (PNC) study (Mason et al., 2015), focusing on 46 adolescents of the sample of 119 who reported heavy cannabis use at baseline. Urban adolescents (91% African American) presenting for primary health care were randomized to intervention or control conditions and followed for 6 months. We selected cases (n = 46) to analyze based on heavy cannabis use reported at baseline (≥10 times in past month). The ordinal response data (cannabis use) were modeled using a mixed-effects proportional odds model, including fixed effects for treatment, time, and their interaction, and a subject-level random effect. In the subsample of adolescents with heavy cannabis use, those assigned to PNC had a 35.9% probability of being abstinent at 6 months, compared with a 13.2% probability in the control condition. Adolescents in the PNC condition had a 16.6% probability of using cannabis 10 or more times per month, compared with a 38.1% probability in the control condition. This differs from results of the full sample (N = 119), where no significant effects on cannabis use were found. PNC increased the probability of abstinence and reduced heavy cannabis use. These results provide initial support for PNC as a model for brief treatment with non-treatment seeking adolescents who are heavy users of cannabis.

Quality of life and recreational cannabis use.

Cannabis is now the most commonly used illicit drug in the United States and use is increasing. Frequent cannabis use has been associated with adverse social and health effects. We sought to evaluate the relationship between recreational cannabis use and Quality of Life (QoL), a person-centered measure that characterizes the overall sense of health and wellbeing. We hypothesized that QoL would be unchanged or increased among recreational cannabis users, who did not meet criteria for a Cannabis Use Disorder (CUD) and that QoL would be lower among those who met criteria for a CUD. We conducted a systematic review, employing guidelines from Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). The results were categorized into tables and identified trends. Fourteen studies met our pre-defined selection criteria. The studies were heterogeneous and their quality was low. With one exception, we did not identify any population for whom cannabis use was associated with improved QoL. QoL was lower in persons who used cannabis heavily, or who met criteria for CUD. However, this association was inconsistent and the magnitude was weaker than the relationship between QoL and use of other addictive substances (including tobacco and illicit drugs). In this systematic review, heavy cannabis use or CUD was associated with reduced QoL. It is unknown whether reduced QoL drives cannabis use, or whether cannabis use can lead to reduced QoL. Prospective studies are needed to evaluate the causal relationship between cannabis and QoL. Furthering the understanding of the relationship between cannabis and QoL can inform public policy, prevention efforts, outcomes, and an objective understanding of the effects of cannabis users. (Am J Addict 2017;26:8-25).

Attentional retraining and cognitive biases in a regular cannabis smoking student population

Abstract. Aim Repeated drug use can lead to attentional bias and approach tendencies, which are thought to play an important role in problematic substance use and dependence. The aims of the current study were to 1) test an attentional retraining procedure in a sample of moderate and heavy cannabis using students and 2) compare baseline attentional and approach bias between the two groups with different implicit measures. Design and participants Attentional bias scores toward cannabis-related or neutral stimuli were determined with modified versions of the Visual Probe Task and the cannabis Stroop task. Approach and avoidance action tendencies toward cannabis-related and neutral stimuli were assessed with the cannabis Approach-Avoidance Task (AAT) and the Stimulus Response Compatibility task (SRC). Seventeen participants were assigned randomly to five sessions of an attentional retraining procedure or control training. Results Attentional retraining did not decrease the speeded detection of cannabis stimuli and the difficulty to disengage from those stimuli, no trainingseffects were revealed. Moderate cannabis users did not show an attentional bias for cannabis-related cues (measured with the cannabis Stroop task), whereas heavy cannabis users did show an attentional bias for cannabis-related stimuli that cannot be attributed to cognitive control deficits on the classical Stroop task. Moreover, heavy cannabis users, but not moderate users, were significant faster to approach cannabis images compared to neutral images, using the SRC task. Conclusion Seen the observed difference in cognitive biases towards cannabis stimuli between moderate and heavy cannabis users, this study supports the allegation that cognitive biases towards cannabis stimuli may be an important marker of problematic cannabis use.

Assessing cannabis consumption frequency: Is the combined use of free and glucuronidated THCCOOH blood levels of diagnostic utility?

Heavy cannabis consumption is considered incompatible with safe driving. In Swiss traffic policy, drivers suspected of regular cannabis use are therefore required to undergo medical assessment of their long-term fitness to drive. A whole blood concentration of the cannabis metabolite 11-nor-9-carboxy-Δ9 -tetrahydrocannabinol (THCCOOH) of 40 µg/L is currently used by Swiss forensic experts as the decision limit for regular cannabis consumption. The present study aimed to investigate the suitability of THCCOOH-glucuronide blood levels as an additional and/or better marker for the frequency of cannabis use. Whole blood samples collected from 23 heavy (≥10 joints/month) and 25 occasional smokers (≥1 joint/month, but ≤ 1 joint/week) enrolled in a placebo-controlled cannabis smoking study were analyzed for THCCOOH and THCCOOH-glucuronide. Based on receiver operating characteristic (ROC) curve analysis, concentration thresholds could be established for distinguishing between these two groups. Proposed thresholds for heavy use were THCCOOH-glucuronide > 52 µg/L (100% specificity; 41% sensitivity) and/or total THCCOOH > 58 µg/L (100% specificity; 43% sensitivity). Optimum thresholds for occasional use were THCCOOH-glucuronide < 5 µg/L (73% specificity; 97% sensitivity) and/or total THCCOOH < 5 µg/L (62% specificity; 98% sensitivity). Our results indicate that the THCCOOH-glucuronide whole blood concentration is a useful parameter that complements the free THCCOOH level to assess the frequency of cannabis consumption. The consideration of the blood concentrations of both free and glucuronidated THCCOOH improves the identification of heavy users whose fitness to drive has to be carefully assessed. Copyright © 2016 John Wiley & Sons, Ltd.

Opposing Effects of Cannabis Use on Late Auditory Repetition Suppression in Schizophrenia Patients and Healthy Control Subjects

BackgroundChronic cannabis use may cause neurocognitive deficits and increase the risk of psychosis. Nevertheless, the effects of cannabis use on neurocognitive functioning in schizophrenia have remained largely unspecified. MethodsHere, we studied repetition suppression of auditory event-related responses in a paired-stimulus design in a mixed sample of schizophrenia patients (n = 34) and healthy control subjects (n = 45) with chronic heavy cannabis use and schizophrenia patients (n = 33) and healthy control subjects (n = 61) without cannabis use. ResultsRepeated measures analysis yielded an overall significant reduction of P50 amplitude between first and second stimulus (p < .02), which was not different between the groups, a reduction of N100 amplitude, which was different for schizophrenia patients compared with healthy control subjects independent of cannabis use (p < .02), and a significant interaction between diagnosis and chronic cannabis use on the reduction of the P200 amplitude (p < .001). While chronic cannabis use was related with increased P200 suppression ratios in control subjects (with chronic cannabis use: 0.55 ± 0.04; without chronic cannabis use: 0.40 ± 0.03; p < .02), the reverse effect was found in schizophrenia (with chronic cannabis use: 0.36 ± 0.05; without chronic cannabis use: 0.54 ± 0.05; p < .02). This result remained significant after inclusion of potential confounders. Total lifetime cannabis use showed a significant correlation with the P200 suppression ratio in otherwise healthy control subjects (r = .28, p < .007). By contrast, the duration of time since last cannabis use was significantly correlated with the P200 suppression ratio in schizophrenia patients (r = .42, p < .002). ConclusionsIn aggregate, these diverging effects of chronic cannabis use on P200 repetition suppression may suggest underlying alterations in the endocannabinoid system in schizophrenia.

P.6.e.004 - Cannabis dependence and the brain reward system: disentangling the role of exposure and addiction related effects

Evidence that long-term cannabis use may be hazardous to white matter in the developing brain has been accumulating, with early onset use in particular thought to impair structural morphology and integrity, during the critical neurodevelopment occurring in adolescence. We found specific localized axonal connectivity disturbances in adult long-term heavy cannabis users, with 84–88% reductions in streamlines in the fimbria of the hippocampus, and commissural fibers extending to the precuneus. White matter integrity within these fiber bundles was associated with the age of onset of cannabis use. The endocannabinoid system is critically involved in axonal growth in the developing brain; mechanisms underlying axonal morphological alterations following exposure to cannabis in utero have been identified. Mechanisms that may be specifically perturbed by cannabis use impacting the neurodevelopment and brain maturational processes that occur during adolescence require further research. Dysfunctional connectivity may underlie a wide range of cognitive disturbances and psychological symptoms, including vulnerability to psychosis, depression, and anxiety disorders, all of which are significant public health concerns.

Heavy Cannabis Use Is Associated With Low Bone Mineral Density and an Increased Risk of Fractures

PurposeTo investigate possible associations between recreational cannabis use and bone health in humans. MethodsCross-sectional study of individuals recruited from primary care in the UK between 2011 and 2013. Cases were regular smokers of cannabis divided into moderate (n = 56) and heavy user (n = 144) subgroups depending on whether they reported fewer or more than 5000 cannabis smoking episodes during their lifetime. Controls comprised 114 cigarette smokers. ResultsHeavy cannabis users had lower total hip bone mineral density (mean ± SD Z-score: −0.20 ± 0.9 vs +0.2 ± 0.9, P < .0005), lower spine bone mineral density (−0.5 ± 1.2 vs 0.0 ± 1.2, P < .0005), and lower body mass index (BMI; 26.5 ± 6.0 vs 29.0 ± 7.0, P = .01) than controls. Fracture rate was also increased in heavy users (rate ratio = 2.17; 95% confidence interval, 1.59-2.95; P < .001). When compared with controls, serum cross-linked C-telopeptide of type 1 collagen (CTX) concentrations were raised in heavy cannabis users (0.3 ± 0.1 vs 0.2 ± 0.1 pg/mL, P = .045), as were serum N-terminal propeptide of type 1 procollagen (P1NP) concentrations (47.1 ± 19.2 vs 41.2 ± 17.8 pg/mL, P = .01). Serum total 25-hydroxyvitamin D concentrations were reduced in heavy users compared with controls (25.3 ± 16.8 vs 36.9 ± 26.7 nmol/L, P = .002). Multiple regression analysis revealed that heavy cannabis use was an independent predictor of spine bone mineral density, accounting for 5.4% of the variance (P = .035), and total hip bone mineral density, accounting for 5.8% of the variance (P = .001), but mediation analysis suggested that the effect on spine bone mineral density was indirect and mediated through low body mass index. ConclusionsHeavy cannabis use is associated with low bone mineral density, low BMI, high bone turnover, and an increased risk of fracture. Heavy cannabis use negatively impacts on bone health both directly and indirectly through an effect on BMI.

The association between cannabis use and suicidality among men and women: A population-based longitudinal study

BackgroundEvidence regarding the role of sex differences in the association between cannabis use and suicidality is lacking. We explored sex differences in the bidirectional association between cannabis use and suicidality in a 3-year longitudinal study. MethodsData were drawn from waves 1 and 2 of the National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). Bidirectional analyses were conducted separately by sex, exploring incidence of suicidality among cannabis users (n=963 vs. 30,586 non-users) as well as initiation of cannabis use among suicidal individuals (n=1805 vs. 25,729 non-suicidal). Cannabis use was categorized based on frequency of use. Multivariate logistic regression analyses controlling for multiple covariates were conducted. ResultsCannabis use was significantly associated with increased incidence of suicidality among men (Adjusted Odds Ratio [AOR] for any cannabis use =1.91[1.02–3.56]) but not among women (AOR=1.19[0.64–2.20]). Daily cannabis use was significantly associated with increased incidence of suicidality among men (AOR=4.28[1.32–13.82]) but not among women (AOR=0.75[0.28–2.05]). Conversely, baseline suicidality was associated with initiation of cannabis use among women (AOR=2.34[1.42–3.87]) but not among men (AOR=1.10[0.57–2.15]). Separate analyses of suicidal ideation and suicide attempts demonstrated a significant association between cannabis use and subsequent incidence of suicidal ideation in men, and a significant association between baseline suicidal ideation and subsequent initiation of cannabis use in women. No significant association was found for the bidirectional association between cannabis use and suicide attempts in either sex. LimitationsSuicidality was assessed only in individuals reporting depressed mood and/or anhedonia. ConclusionsOur findings support a longitudinal association between heavy cannabis use and the incidence of suicidality in men, but not in women. Conversely, baseline suicidality is longitudinally associated with the initiation of cannabis use in women, but not in men. This may have implications on clinical and social aspects of cannabis use and merit further research into the unique effects of sex differences on cannabis induced psychopathology.

Heavy cannabis users at elevated risk of stroke: evidence from a general population survey

Objective:Case reports and hospital‐based case–control studies suggest that cannabis use may increase the risk of stroke. We examined the risk of non‐fatal stroke or transient ischemic attack (TIA) among cannabis users in the general community. Method:A general population survey of Australians aged 20–24 years (n=2,383), 40–44 years (n=2,525) and 60–64 years (n=2,547) was used to determine the odds of lifetime stroke or TIA among participants who had smoked cannabis in the past year while adjusting for other stroke risk factors. Results:There were 153 stroke/TIA cases (2.1%). After adjusting for age cohort, past year cannabis users (n=1,043) had 3.3 times the rate of stroke/TIA (95% CI 1.8–6.3, p<0.001). The incidence rate ratio (IRR) reduced to 2.3 after adjustment for covariates related to stroke, including tobacco smoking (95% CI 1.1–4.5). Elevated stroke/TIA was specific to participants who used cannabis weekly or more often (IRR 4.7, 95% CI 2.1–10.7) with no elevation among participants who used cannabis less often. Conclusions:Heavy cannabis users in the general community have a higher rate of non‐fatal stroke or transient ischemic attack than non‐cannabis users.

Grey Matter Changes Associated with Heavy Cannabis Use: A Longitudinal sMRI Study.

Cannabis is the most frequently used illicit drug worldwide. Cross-sectional neuroimaging studies suggest that chronic cannabis exposure and the development of cannabis use disorders may affect brain morphology. However, cross-sectional studies cannot make a conclusive distinction between cause and consequence and longitudinal neuroimaging studies are lacking. In this prospective study we investigate whether continued cannabis use and higher levels of cannabis exposure in young adults are associated with grey matter reductions. Heavy cannabis users (N = 20, age baseline M = 20.5, SD = 2.1) and non-cannabis using healthy controls (N = 22, age baseline M = 21.6, SD = 2.45) underwent a comprehensive psychological assessment and a T1- structural MRI scan at baseline and 3 years follow-up. Grey matter volumes (orbitofrontal cortex, anterior cingulate cortex, insula, striatum, thalamus, amygdala, hippocampus and cerebellum) were estimated using the software package SPM (VBM-8 module). Continued cannabis use did not have an effect on GM volume change at follow-up. Cross-sectional analyses at baseline and follow-up revealed consistent negative correlations between cannabis related problems and cannabis use (in grams) and regional GM volume of the left hippocampus, amygdala and superior temporal gyrus. These results suggests that small GM volumes in the medial temporal lobe are a risk factor for heavy cannabis use or that the effect of cannabis on GM reductions is limited to adolescence with no further damage of continued use after early adulthood. Long-term prospective studies starting in early adolescence are needed to reach final conclusions.

Consumo intensivo de alcohol y cannabis, y prácticas sexuales de riesgo en estudiantes universitarios

ObjectiveTo determine the incidence of unsafe sex among university students and its association with heavy episodic drinking (HED) and cannabis use. MethodA cohort study was carried out from 2005 to 2011 among university students of the Compostela Cohort (n=517). HED was measured using the third question of the Alcohol Use Disorders Identification Test (AUDIT). Unsafe sex was considered to be sex under the influence of alcohol (SUA) and sex without a condom (SWC). Logistic regression models were created. ResultsThe incidence of SUA was 40.9% for women and 53.0% for men, while the SWC incidence ranged from 13.7% for women to 25.7% for men. HED and cannabis use were associated with SUA in both women (OR=2.08, 95% CI: 1.03-4.21; OR=2.78, 95%CI: 1.57-4.92) and men (OR=4.74 (95%CI: 1.49-15.09; OR=4.37, 95%CI: 1.17- 16.36). Moreover, cannabis use in women was associated with SWC (OR=2.96, 95%CI: 1.52-5.75). The population attributable fractions of SUA for HED were 24.7% and 52.9% for women and men, respectively. ConclusionsHED and cannabis use represent a public health problem due to their association with a variety of problems, including engagement in unsafe sex. Our results suggest that a significant proportion of unsafe sex could be avoided by reducing this consumption pattern of alcohol.

Treatment of Cannabis Use Disorder: Current Science and Future Outlook.

Cannabis is the most commonly used illicit substance in the United States. Rates of cannabis use and cannabis use disorder (CUD) have increased in the past decade, paralleling changes in the legal and political climate favoring legalization. Almost 20 million people 12years or older report past-month cannabis use, and 8million report daily or near-daily use. Concurrently, the perception that cannabis use poses a significant risk of negative consequences has decreased. Contrary to this perception, heavy cannabis use is associated with cognitive impairment, increased risk for psychotic disorders and other mental health problems, lower education attainment, and unemployment. Clinical trials of various treatments for CUD have likewise increased, focusing primarily on psychotherapy treatments, specifically motivational enhancement therapy, cognitive behavioral therapy, and contingency management. Their findings suggest that a combination of these three modalities produces the best abstinence outcomes, although abstinence rates remain modest and decline after treatment. More recently, pharmacotherapy trials have been conducted as adjunctive interventions to psychosocial treatment. N-acetylcysteine and gabapentin are two of the most promising medications, although no pharmacologic treatment has emerged as clearly efficacious. In this review, we provide a detailed summary of clinical trials that evaluated psychotherapy and pharmacotherapy for treating CUD and discuss emerging areas of clinical research and cannabis-specific barriers to treatment.

Cannabis, Psychosis, and Mortality: A Cohort Study of 50,373 Swedish Men.

The authors assessed 1) the overall risk of death among cannabis users compared with nonusers and the extent to which psychosis affects excess mortality; 2) mortality among persons with psychotic disorders and the extent to which cannabis use affects excess mortality; and 3) the interaction effect of cannabis use and diagnosis of psychotic disorders on mortality. This was a longitudinal study of 50,373 Swedish male military conscripts (ages 18-19) who were followed in the National Cause of Death Register up to around age 60. Cox proportional hazard modeling was used to assess risk of death in relation to baseline cannabis use and diagnosis of psychotic disorders. Subjects with a baseline history of heavy cannabis use had a significantly higher risk of death (hazard ratio=1.4, 95% CI=1.1, 1.8) than those without such a history. The authors found an excess mortality among subjects with psychotic disorders, but the level did not differ between those with a history of cannabis use (ever users: hazard ratio=3.8, 95% CI=2.8, 5.0; heavy users: hazard ratio=3.8, 95% CI=2.6, 6.2) and those without such a history (hazard ratio=3.7, 95% CI=3.1, 44). No interaction was observed between cannabis use and diagnosis of psychotic disorders with regard to mortality. The results suggest that individuals with an early history of heavy use of cannabis are at a higher risk of death than those with a history of no use of cannabis. Although the authors adjusted for several confounders at baseline, the results should be interpreted with caution because of a lack of information on confounders in the period after conscription.

Attenuated frontal and sensory inputs to the basal ganglia in cannabis users.

Heavy cannabis use is associated with reduced motivation. The basal ganglia, central in the motivation system, have the brain's highest cannabinoid receptor density. The frontal lobe is functionally coupled to the basal ganglia via segregated frontal-subcortical circuits conveying information from internal, self-generated activity. The basal ganglia, however, receive additional influence from the sensory system to further modulate purposeful behaviors according to the context. We postulated that cannabis use would impact functional connectivity between the basal ganglia and both internal (frontal cortex) and external (sensory cortices) sources of influence. Resting-state functional connectivity was measured in 28 chronic cannabis users and 29 controls. Selected behavioral tests included reaction time, verbal fluency and exposition to affective pictures. Assessments were repeated after one month of abstinence. Cannabis exposure was associated with (1) attenuation of the positive correlation between the striatum and areas pertaining to the 'limbic' frontal-basal ganglia circuit, and (2) attenuation of the negative correlation between the striatum and the fusiform gyrus, which is critical in recognizing significant visual features. Connectivity alterations were associated with lower arousal in response to affective pictures. Functional connectivity changes had a tendency to normalize after abstinence. The results overall indicate that frontal and sensory inputs to the basal ganglia are attenuated after chronic exposure to cannabis. This effect is consistent with the common behavioral consequences of chronic cannabis use concerning diminished responsiveness to both internal and external motivation signals. Such an impairment of the fine-tuning in the motivation system notably reverts after abstinence.

Heavy cannabis use and attentional avoidance of anxiety-related stimuli

ObjectivesCannabis is now the most widely used illicit substance in the world. Previous research demonstrates that cannabis use is associated with dysfunctional affect regulation and anxiety. Anxiety is characterised by attentional biases in the presence of emotional information. This novel study therefore examined the attentional bias of cannabis users when presented with anxiety-related stimuli. The aim was to establish whether cannabis users respond to anxiety-related stimuli differently to control participants. MethodsA dot-probe paradigm was utilised using undergraduate students. Trials contained anxiety-related stimuli and neutral control stimuli. Eye-tracking was used to measure attention for the stimuli. ResultsResults indicated that cannabis users demonstrated attentional-avoidance behaviour when presented with anxiety-related stimuli. ConclusionsThe findings suggest a difference in processing of emotional information in relation to neutral information between groups. It would appear that cannabis users avoid anxiety provoking stimuli. Such behaviour could potentially have motivational properties that could lead to exacerbating anxiety disorder-type behaviour.

Heavy cannabis use impairs verbal memory of first psychotic episode patients

IntroductionCannabis consumption is known to be increased in both schizophrenic and first psychotic episode patients. Contrary to what has been reported in studies with healthy people, all published studies so far have reported no impairments or even beneficial effects on neurocognition associated with cannabis consumption in schizophrenia and first psychotic episode patients. However, these studies did not address the effects of very high cannabis consumption.ObjectiveOur aim in this study was to assess the effects on neurocognition of regular and heavy cannabis consumption in first psychotic episode patients.MethodsA total of 74 patients were included in the study and assigned to 3 different groups according to their mean cannabis consumption during the last year (non-users, regular users, and heavy users). Participants were administered verbal memory, attention, processing speed, working memory, vocabulary, arithmetic and spatial orientation tasks.ResultsOur results showed the heavy cannabis group of first psychotic episode patients to be significantly impaired in all the verbal memory measures with respect to the non-users group. There were no significant differences between regular users and non-users. Moreover, regular cannabis consumption was associated with an improvement in some attention and processing speed measures.ConclusionsOur data showed heavy cannabis consumption to impair verbal memory in first psychotic episode patients and suggest a dose-related effect of cannabis consumption, since regular consumption did not impair verbal memory and may be beneficial for other tasks.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Cannabis use and symptoms of anxiety in adolescence and the moderating effect of the serotonin transporter gene.

There is substantial evidence for the assumption that particularly heavy cannabis usett is associated with a variety of psychopathologic conditions. Little is known about the relationship between cannabis and anxiety. Prior studies have concluded that cannabis use alone is not sufficient for the development of long-term anxiety, and it has been suggested that cannabis is simply a risk factor that operates in conjunction with other risk factors. One such risk factor may be an individuals' genetic vulnerability. The present study examines the relationship between cannabis use and symptoms of anxiety by taking a developmental molecular-genetic perspective with a focus on a polymorphism involved in the regulation of serotonin. Specifically, we concentrated on changes in cannabis use and symptoms of anxiety over time and differences herein for individuals with and without the short allele of the 5-HTTLPR genotype. Data were from 1424 adolescents over a period of 5 years. We used different statistical analyses to test co-development of cannabis use and symptoms of anxiety throughout adolescence and the possible role of the 5-HTTLPR genotype in this process. Results from different analyses showed that cannabis use is associated with an increase in symptoms of anxiety, but only in carriers of the short allele of the 5-HTTLPR genotype, not in non-carriers. The findings of the present study show first evidence that the links between cannabis use and symptoms of anxiety are conditional on the individuals' genetic make-up.

A literature review and meta-analyses of cannabis use and suicidality

BackgroundWe lack a review of the epidemiological literature on cannabis use (acute use and chronic-usual quantity/frequency and heavy use) and suicidality (suicide death, suicide ideation, suicide attempt). MethodsThe English language literature on Medline, PsychInfo, Google Scholar, and public-use databases was searched for original articles, critical review reports, and public use data on cannabis use and suicide for the period ranging from 1990–2015 (February). Odds ratios (OR) from random effects in meta-analyses for any cannabis use and heavy cannabis use were calculated. ResultsThe acute cannabis-suicidality literature mostly includes descriptive toxicology reports. In terms of death by suicide, the average positive cannabis rate was 9.50% for studies sampling from all suicides, with higher cannabis detection rates amongst suicide decedents by non-overdose methods. We found only 4 studies providing estimates for any chronic cannabis use and death by suicide (OR=2.56 (1.25–5.27)). After deleting duplicates we found 6 studies on any cannabis use and suicide ideation (OR=1.43 (1.13–1.83)), 5 studies on heavy cannabis use and suicide ideation (OR=2.53 (1.00–6.39)), 6 studies on any cannabis use and suicide attempt (OR=2.23 (1.24–4.00)) and 6 studies on heavy cannabis use and suicide attempt (OR=3.20 (1.72–5.94)). ConclusionsWe currently lack evidence that acute cannabis use increases imminent risk for suicidality. The evidence tends to support that chronic cannabis use can predict suicidality, but the lack of homogeneity in the measurement of cannabis exposure and, in some instances, the lack of systematic control for known risk factors tempered this finding.