Effects of THC on behavioral measures of impulsivity in humans

Gambling and Cannabis Use: Clinical and Policy Implications

Eleven US States and the District of Columbia legally allow personal (i.e., recreational) cannabis use by adults, and an additional 22 states allow use of cannabis for medicinal purposes. Of these jurisdictions, only two do not have some form of legalized gambling available (https://www.casino.org/local/guide/). In contrast to this rapid increase in legally available marijuana is the limited knowledge about the intersection of cannabis use and gambling. This paper strives to define the current status of the relevant literatures and consider the implication for future gambling research. We describe the research literature on the prevalence of cannabis use and co-existing gambling problems and the effects of cannabis use on gambling-related cognitive functions and decision-making. We also discuss clinical considerations with treating problem gamblers with a cannabis use disorder. Finally, the potential implications for responsible gambling practices and policies and the most pressing gaps in the research literature are offered.

Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol

BACKGROUND

Acute consumption of cannabis or its primary psychoactive ingredient ∆9-tetrahydrocannabinol has been shown to impair memory, reaction time, time perception, and attention. However, it is difficult to measure these impairments in a brief test that can be used in a non-laboratory setting.

AIMS

We aim to develop and validate a prototype for a mobile phone application to measure ∆9-tetrahydrocannabinol-induced cognitive impairment.

METHODS

We conducted two double-blind, within-subjects studies examining impairments after oral doses of ∆9-tetrahydrocannabinol (0, 7.5, 15 mg) using both standardized computer-based tasks and our novel phone-based tasks. The tasks measured cognitive speed, reaction time, fine motor ability, and working memory and, in the second study, time perception. Study 1 (n=24) provided initial data, and Study 2 (n=24) was designed to refine the measures. In both studies, healthy non-daily cannabis users participated in three four-hour experimental sessions in which they received capsules containing ∆9-tetrahydrocannabinol (7.5, 15 mg) or placebo. Subjective and cardiovascular measures were obtained at regular intervals, and at the time of peak drug effect subjects completed both standardized, computer-based and brief, phone-based tasks.

RESULTS

∆9-Tetrahydrocannabinol-induced impairment was detected on most of the computer tasks, but was not evident on most of the phone tasks.

CONCLUSIONS

The phone tasks were brief, to facilitate use in a non-laboratory setting, but it is likely that this made them less sensitive to the impairing effects of ∆9-tetrahydrocannabinol. These findings confirm that ∆9-tetrahydrocannabinol impairs performance on several tasks at two recreationally relevant doses, but raises question about the feasibility of designing a phone application as a sensitive field sobriety test for cannabis.

Dysregulation as a correlate of cannabis use and problem use

OBJECTIVE

Cannabis users with a dysregulatory risk factor may be particularly vulnerable to engaging in more frequent and problematic cannabis use. Contemporary models of dysregulated behavior suggest that dysregulation emerges due to distinct mechanisms. The current study seeks to examine the dysregulatory correlates of cannabis involvement, including working memory capacity, delay discounting, impulsivity, and reward sensitivity.

METHOD

Participants were 104 non-treatment seeking frequent cannabis users (the average participant used cannabis 71% of the days/past 60 days [SD = 22%], with an average of two uses per day [SD = 1.2]). Mean age was 21.3 (SD = 4.3); 36.5% were female. Working memory was assessed via the Trail-Making Test-B and the Digit Span subtests of the WAIS-III, delay discounting was assessed via a computer-based task, trait impulsivity was self-reported via the Barratt Impulsiveness Scale, and reward sensitivity was self-reported via the Reward Dependence Scale and the Snaith-Hamilton Pleasure Scale.

RESULTS

Structural equation modeling estimated the associations between different facets of dysregulation and cannabis involvement. Results suggest that poor working memory capacity and high trait impulsivity were associated with both use and problem use. Greater delay discounting was associated with problem use, but not with frequency of use. Low reward sensitivity was associated with more frequent cannabis use, but not with problem use.

CONCLUSIONS

Results confirm that the dysregulatory correlates of cannabis involvement consist of multiple dimensions of functioning. Prospective studies that assess the multidimensional structure of dysregulation and cannabis involvement are needed in order to disaggregate the dysregulatory antecedents and consequences of cannabis involvement.

Feasibility and effects of galantamine on cognition in humans with cannabis use disorder

BACKGROUND

As long-term use of medicinal and recreational cannabis becomes more common and concentrations of delta-9-tetrahydrocannabinol (THC) in cannabis increase, it is timely to identify strategies to counteract the cognitive effects of cannabinoids.

OBJECTIVE

Galantamine is an acetylcholinesterase inhibitor approved for the treatment of Alzheimer's disease and other dementias. This study aimed to investigate the feasibility of galantamine administration to individuals with cannabis use disorder (CUD), and the effects of galantamine on cognition. We hypothesized galantamine would be well tolerated and would not have procognitive effects in the absence of acute cannabis intoxication.

METHODS

Thirty individuals with CUD (73.5% male, 26.5% female) participated in a randomized, double-blind, parallel-group trial. Participants completed a baseline session followed by a 10-day outpatient treatment period, during which they received either 8 mg/day of galantamine orally or placebo. Cognitive assessments were conducted at three time points and self-reported measures that may impact cognitive performance (cannabis withdrawal, craving, and mood) were completed at six time points.

RESULTS

There were no significant differences in demographic and baseline variables between groups (galantamine vs. placebo). There were no significant adverse effects from galantamine. Cannabis withdrawal and craving continuously decreased over the study. We saw evidence of a modest improvement in cognitive outcomes during the 10-day period, exemplified by a statistically significant increase in measures of response inhibition (increased median reaction time on the Stop Signal Task), and a trend for improvement in measures of attention (increased RVP A'), for both groups. Analyses did not show, however, a significant main effect for treatment or treatment-by-time interactions.

CONCLUSIONS

The findings of this pilot study support the feasibility of the administration of galantamine for individuals with CUD. Adequately powered, randomized, placebo-controlled trials are required to investigate the potential of galantamine to improve cognitive deficits associated with CUD.

Effects of morphine/CP55940 mixtures on an impulsive choice task in rhesus monkeys

µ-Opioid receptor agonists are commonly used to treat pain despite their adverse effects. In preclinical studies, cannabinoid receptor agonists increase the potency of opioids for producing antinociceptive but not reinforcing effects. It is unknown whether other adverse effects of these drugs, such as impairment of complex behavior, are enhanced by their co-administration. This study characterized the effects of morphine (µ-opioid receptor agonist; 0.32-5.6 mg/kg, subcutaneously) and CP55940 (CB1/CB2 cannabinoid receptor agonist; 0.0032-0.32 mg/kg, subcutaneously), alone and in mixtures, in monkeys (n=3) choosing between one pellet delivered immediately and two pellets delivered after a delay. Two consecutive choices of the immediate or delayed reward decreased or increased, respectively, the delay. The median adjusted delay, indicating indifference between the immediate and delayed reinforcers, was increased by morphine (3.2 mg/kg) and CP55940 (0.01-0.032 mg/kg). Performance after administration of morphine (0.32 and 1 mg/kg)/CP55940 (0.0032-0.032 mg/kg) mixtures was not different from performance after CP55940 alone. Neither morphine, CP55940, nor mixtures decreased the median adjusted delay (i.e. increased impulsivity). These findings failed to confirm previous studies showing that morphine increases impulsivity, perhaps because of procedural differences among studies. Treatment of pain often requires repeated drug administration; thus, it remains to be determined whether the present findings predict the effects of chronically administered morphine/CP5540 mixtures on impulsive choice.

Two days of calorie deprivation impairs high level cognitive processes, mood, and self-reported exertion during aerobic exercise: A randomized double-blind, placebo-controlled study

Military personnel and emergency responders perform cognitively-demanding tasks during periods of sustained physical exertion and limited caloric intake. Cognitive function is preserved during short-term caloric restriction, but it is unclear if preservation extends to combined caloric restriction and physical exertion. According to the "reticular-activating hypofrontality" model, vigorous exertion impairs prefrontal cortex activity and associated functions. This double-blind, placebo-controlled, crossover study examined cognitive function during sustained exertion while volunteers were calorically-deprived. Twenty-three volunteers were calorie-depleted for two days on one occasion and fully-fed on another. They completed intermittent bouts of exercise at 40-65% VO_2peak while prefrontal cortex-dependent tasks of cognitive control, mood, and perceived exertion were assessed. Calorie deprivation impaired accuracy on the task-switching task of set-shifting (p < .01) and decreased sensitivity on the go/no-go task of response inhibition (p < .05). Calorie deprivation did not affect risk taking on the Rogers risk task. During exercise, calorie deprivation, particularly on day 2, increased perceived exertion (p < .05) and impaired mood states of tension, depression, anger, vigor, fatigue, and confusion (all p < .01). Physical exertion during severe calorie deprivation impairs cognitive control, mood, and self-rated exertion. Reallocation of cerebral metabolic resources from the prefrontal cortex to structures supporting movement may explain these deficits.

Caffeine and cannabinoid receptors modulate impulsive behavior in an animal model of attentional deficit and hyperactivity disorder

Attention deficit and hyperactivity disorder (ADHD) is characterized by impaired levels of hyperactivity, impulsivity, and inattention. Adenosine and endocannabinoid systems tightly interact in the modulation of dopamine signaling, involved in the neurobiology of ADHD. In this study, we evaluated the modulating effects of the cannabinoid and adenosine systems in a tolerance to delay of reward task using the most widely used animal model of ADHD. Spontaneous Hypertensive Rats (SHR) and Wistar-Kyoto rats were treated chronically or acutely with caffeine, a non-selective adenosine receptor antagonist, or acutely with a cannabinoid agonist (WIN55212-2, WIN) or antagonist (AM251). Subsequently, animals were tested in the tolerance to delay of reward task, in which they had to choose between a small, but immediate, or a large, but delayed, reward. Treatment with WIN decreased, whereas treatment with AM251 increased the choices of the large reward, selectively in SHR rats, indicating a CB₁ receptor-mediated increase in impulsive behavior. An acute pre-treatment with caffeine blocked WIN effects. Conversely, a chronic treatment with caffeine increased the impulsive phenotype and potentiated the WIN effects. The results indicate that both cannabinoid and adenosine receptors modulate impulsive behavior in SHR: the antagonism of cannabinoid receptors might be effective in reducing impulsive symptoms present in ADHD; in addition, caffeine showed the opposite effects on impulsive behavior depending on the length of treatment. These observations are of particular importance to consider when therapeutic manipulation of CB1 receptors is applied to ADHD patients who consume coffee.

The role of substance use, smoking, and inflammation in risk for suicidal behavior

BACKGROUND

Alcohol and substance use disorders are important predictors for suicidal behavior. However, the role of individual substances as proximal risk factors for suicidal behavior and the mechanisms through which substance use affect risk are not entirely clear. We examine whether the frequency of substance use and whether biological markers in the HPA axis and inflammatory pathways are associated with clinical risk factors of suicidal behavior of aggression, impulsivity, hopelessness, and poor sleep.

METHODS

The sample consisted of psychiatric inpatients, aged 15-30 years, admitted for suicide attempt (n = 38), suicidal ideation (n = 40); and healthy controls (n = 37). We measured hair cortisol concentrations, glucocorticoid receptor (GR) sensitivity, stimulated production of interleukin- or IL-6, C-reactive protein, and mRNA expression of GR, SKA2, FKBP5, TNF-α, and IL-1β.

RESULTS

Smoking was associated with increased aggression [β = 2.9, 95% CI (-0.03, 6), p = 0.05], impulsivity [β = 3.1, 95% CI (1.6, 4.6), p < 0.001], and poor sleep [β = 0.5, 95% CI (0.03, 0.95), p = 0.04] even after controlling for demographics and group. Similarly, TNF-α mRNA was associated with impulsivity [β = 0.07, 95% CI (0.01, 0.1), p = 0.02] and hopelessness [β = 0.03, 95% CI (0.004, 0.05), p = 0.03]. Smoking tobacco (r = 0.32, p < 0.001) was positively associated with TNF-α mRNA.

LIMITATIONS

Study limitations include the cross-sectional design, retrospective assessment, and relatively small sample size.

CONCLUSIONS

Future longitudinal studies are needed to test whether inflammatory markers mediate the relationships between smoking, clinical risk factors, and suicidal behavior; and to examine whether smoking cessation could reduce the risk for suicidal behavior in at-risk patients.

A Model of Δ9-Tetrahydrocannabinol Self-administration and Reinstatement That Alters Synaptic Plasticity in Nucleus Accumbens

BACKGROUND

Cannabis is the most widely used illicit drug, but knowledge of the neurological consequences of cannabis use is deficient. Two primary components of cannabis are Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD). We established a THC+CBD model of self-administration and reinstated drug seeking to determine if, similar to other addictive drugs, cannabis produces enduring synaptic changes in nucleus accumbens core (NAcore) thought to contribute vulnerability to drug reinstatement.

METHODS

Sprague Dawley rats were trained to self-administer THC+CBD (n = 165) or were used as vehicle self-administering control animals (n = 24). Reinstatement was initiated by context, cues, drug priming, and stress (yohimbine injection). Enduring neuroadaptations produced by THC+CBD self-administration were assayed using four measures: dendritic spine morphology, long-term depression, alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid/N-methyl-D-aspartate ratios, and behavioral pharmacology.

RESULTS

We described a novel rodent model of cannabis relapse involving intravenous THC+CBD self-administration and drug seeking induced by conditioned context, cues, and stress. Cued reinstatement of THC+CBD seeking depended on a sequence of events implicated in relapse to other addictive drugs, as reinstatement was prevented by daily treatment with N-acetylcysteine or acute intra-NAcore pretreatment with a neuronal nitric oxide synthase or matrix metalloprotease-9 inhibitor, all of which normalize impaired glutamate homeostasis. The capacity to induce N-methyl-D-aspartate long-term depression in NAcore medium spiny neurons was abolished and dendritic spine density was reduced, but alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid/N-methyl-D-aspartate ratio was unaltered in THC+CBD-trained animals, akin to opioids, but not to psychostimulants.

CONCLUSIONS

We report enduring consequences of THC+CBD use on critical relapse circuitry and synaptic physiology in NAcore following rat self-administration and provide the first report of cue- and stress-induced reinstatement with this model.

Affect and cannabis use in daily life: a review and recommendations for future research

BACKGROUND

Although cannabis is often used for the purposes of relieving negative affective states such as anxiety and depression, the associations between cannabis use and affect in daily life are unclear. Ecological momentary assessment (EMA) has been used to study these associations in individuals' natural environments, providing more ecological validity, minimizing retrospective bias, and allowing for the analysis of within-individual processes over time. This review focuses on studies that utilized EMA to examine daily-life associations of cannabis use and negative and positive affective states.

METHODS

We review the findings of the 19 articles that met inclusion criteria, including clinical and community samples.

RESULTS

Results provide equivocal evidence regarding relations between cannabis use and affect for community samples. Findings are mixed for clinical samples as well, but more consistent patterns emerge for general negative affect (NA) and anger/hostility at the momentary level; cannabis use may be more likely following increased NA and lead to decreases in NA and anger/hostility in psychiatric populations.

CONCLUSIONS

Findings support a negative reinforcement hypothesis for clinical samples in terms of general NA and anger/hostility. However, discrepancies among studies point to a need to thoroughly characterize samples, consider motives for and expectancies of use, improve quantification of cannabis use, and consider co-use with other substances. Additional design recommendations are also offered for future studies.

Exploring the association of legalisation status of cannabis with problematic cannabis use and impulsivity in the USA

Background

There has been an increased trend towards the legalisation of medicinal and recreational cannabis use worldwide. This has been controversial as the long-term effects of frequent cannabis use on the brain are still poorly understood.

Methods

In this study, we investigated whether the legal status of cannabis in the United States of America (USA) is associated with problematic cannabis use and impulsivity in 329 frequent cannabis users. The data were collected in 2015 and were analysed in 2017. Ethical approval for this study was obtained from Monash University in 2015.

Results

The results indicated that participants’ problematic cannabis use and impulsivity was not different whether they resided in states where cannabis is legal for medical and/or recreational use or prohibited.

Limitations

The present study is a cross-sectional design, making it difficult to infer causality and establish whether cannabis use is a cause, consequence, or correlate of altered impulsivity.

Conclusion

Our study supports the notion that frequent cannabis use is associated with impulsive behaviours, whilst, conversely, we did not find an association between US state legalisation and problematic cannabis use or impulsivity.

Effects of Δ9-THC and cannabidiol vapor inhalation in male and female rats

RATIONALE

Previous studies report sex differences in some, but not all, responses to cannabinoids in rats. The majority of studies use parenteral injection; however, most human use is via smoke inhalation and, increasingly, vapor inhalation.

OBJECTIVES

To compare thermoregulatory and locomotor responses to inhaled ∆⁹-tetrahydrocannabinol (THC), cannabidiol (CBD), and their combination using an e-cigarette-based model in male and female rats METHODS: Male and female Wistar rats were implanted with radiotelemetry devices for the assessment of body temperature and locomotor activity. Animals were then exposed to THC or CBD vapor using a propylene glycol (PG) vehicle. THC dose was adjusted via the concentration in the vehicle (12.5-200 mg/mL) and the CBD (100, 400 mg/mL) dose was also adjusted by varying the inhalation duration (10-40 min). Anti-nociception was evaluated using a tail-withdrawal assay following vapor inhalation. Plasma samples obtained following inhalation in different groups of rats were compared for THC content.

RESULTS

THC inhalation reduced body temperature and increased tail-withdrawal latency in both sexes equivalently and in a concentration-dependent manner. Female temperature, activity, and tail-withdrawal responses to THC did not differ between estrus and diestrus. CBD inhalation alone induced modest hypothermia and suppressed locomotor activity in both males and females. Co-administration of THC with CBD, in a 1:4 ratio, significantly decreased temperature and activity in an approximately additive manner and to similar extent in each sex. Plasma THC varied with the concentration in the PG vehicle but did not differ across rat sex.

CONCLUSION

In summary, the inhalation of THC or CBD, alone and in combination, produces approximately equivalent effects in male and female rats. This confirms the efficacy of the e-cigarette-based method of THC delivery in female rats.

How Substance Users With ADHD Perceive the Relationship Between Substance Use and Emotional Functioning

OBJECTIVE

Although substance use (SU) is elevated in ADHD and both are associated with disrupted emotional functioning, little is known about how emotions and SU interact in ADHD. We used a mixed qualitative-quantitative approach to explore this relationship.

METHOD

Narrative comments were coded for 67 persistent (50 ADHD, 17 local normative comparison group [LNCG]) and 25 desistent (20 ADHD, 5 LNCG) substance users from the Multimodal Treatment Study of Children with ADHD (MTA) adult follow-up (21.7-26.7 years-old).

RESULTS

SU persisters perceived SU positively affects emotional states and positive emotional effects outweigh negative effects. No ADHD group effects emerged. Qualitative analysis identified perceptions that cannabis enhanced positive mood for ADHD and LNCG SU persisters, and improved negative mood and ADHD for ADHD SU persisters.

CONCLUSION

Perceptions about SU broadly and mood do not differentiate ADHD and non-ADHD SU persisters. However, perceptions that cannabis is therapeutic may inform ADHD-related risk for cannabis use.

Modulation of acute effects of delta-9-tetrahydrocannabinol on psychotomimetic effects, cognition and brain function by previous cannabis exposure

Cannabis use has been associated with psychosis and cognitive dysfunction. Some evidence suggests that the acute behavioral and neurocognitive effects of the main active ingredient in cannabis, (-)-trans-Δ9-tetrahydrocannabinol (∆9-THC), might be modulated by previous cannabis exposure. However, this has not been investigated either using a control group of non-users, or following abstinence in modest cannabis users, who represent the majority of recreational users. Twenty-four healthy men participated in a double-blind, randomized, placebo-controlled, repeated-measures, within-subject, ∆9-THC challenge study. Compared to non-users (N=12; <5 lifetime cannabis joints smoked), abstinent modest cannabis users (N=12; 24.5±9 lifetime cannabis joints smoked) showed worse performance and stronger right hemispheric activation during cognitive processing, independent of the acute challenge (all P≤0.047). Acute ∆9-THC administration produced transient anxiety and psychotomimetic symptoms (all P≤0.02), the latter being greater in non-users compared to users (P=0.040). Non-users under placebo (control group) activated specific brain areas to perform the tasks, while deactivating others. An opposite pattern was found under acute (∆9-THC challenge in non-users) as well as residual (cannabis users under placebo) effect of ∆9-THC. Under ∆9-THC, cannabis users showed brain activity patterns intermediate between those in non-users under placebo (control group), and non-users under ∆9-THC (acute effect) and cannabis users under placebo (residual effect). In non-users, the more severe the ∆9-THC-induced psychotomimetic symptoms and cognitive impairments, the more pronounced was the neurophysiological alteration (all P≤0.036). Previous modest cannabis use blunts the acute behavioral and neurophysiological effects of ∆9-THC, which are more marked in people who have never used cannabis.

Evaluation of cognitive functions in individuals with synthetic cannabinoid use disorder and comparison to individuals with cannabis use disorder

The use of synthetic cannabinoid has been increasing throughout the world and has become a major public health problem. The present study aims to investigate the attention, memory, visuospatial and executive functions in individuals with synthetic cannabinoid use disorder and compare the results with findings obtained from individuals with cannabis use disorder and healthy volunteers with no substance use. Fifty-two patients with synthetic cannabinoid use disorder, 45 patients with cannabis use disorder and 48 healthy control group males were included in the study. The neuropsychological test battery was designed to involve ten studies evaluating a large series of cognitive functions. Impairments in attention, memory, executive and visuospatial functions were identified in individuals with synthetic cannabinoid use disorder and these impairments were found to be significantly greater than in individuals with cannabis use disorder and healthy controls. In line with the data obtained from this study; the evaluation of each cognitive function with more comprehensive test batteries and supporting these evaluations with sensitive brain imaging studies are important topics for future research.

Toward a Unifying Account of Impulsivity and the Development of Self-Control

Impulsivity has traditionally been thought to involve various behavioral traits that can be measured using different laboratory protocols. Whereas some authors regard different measures of impulsivity as reflecting fundamentally distinct and unrelated behavioral tendencies (fragmentation approach), others regard those different indexes as analogue forms of the same behavioral tendency, only superficially different (unification approach). Unifying accounts range from mere intuitions to more sophisticated theoretical systems. Some of the more complete attempts at unifying are intriguing but have validity weaknesses. We propose a new unifying attempt based on theoretical points posed by other authors and supplemented by theory and research on associative learning. We then apply these assumptions to characterize the paradigms used to study impulsivity in laboratory settings and evaluate their scope as an attempt at unification. We argue that our approach possesses a good balance of parsimony and empirical and theoretical grounding, as well as a more encompassing scope, and is more suitable for experimental testing than previous theoretical frameworks. In addition, the proposed approach is capable of generating a new definition of impulsivity and outlines a hypothesis of how self-control can be developed. Finally, we examine the fragmentation approach from a different perspective, emphasizing the importance of finding similarities among seemingly different phenomena.

Chronic Δ9-THC in Rhesus Monkeys: Effects on Cognitive Performance and Dopamine D2/D3 Receptor Availability

Cannabis-related impairments to cognitive function may represent novel therapeutic targets for cannabis-use disorder, although the nature, persistence, and reversibility of such deficits remain unclear. Adult male rhesus monkeys (N = 6) responded in the morning on tasks designed to assess different cognitive domains using the Cambridge Neuropsychological Test Automated Battery (CANTAB) touchscreens followed by responding maintained under a fixed-ratio (FR) 10 schedule of food presentation in different operant chambers. First, the acute effects of Δ9-tetrahydrocannabinol (THC; 0.01-0.56 mg/kg, i.v.) on cognitive performance, FR responding, and body temperature were determined. Next, THC (1.0-2.0 mg/kg, s.c.) was administered daily after FR 10 sessions for 12 weeks, during which the residual effects of THC (i.e., 22 hours after administration) on cognition were examined and the acute effects of THC were redetermined. In a subgroup of monkeys, dopamine D2/D3 receptor availability was assessed after 4 weeks of chronic THC exposure and compared with drug-naive controls using positron emission tomography and [11C]-raclopride (N = 4/group). Acute THC pretreatments dose-dependently decreased FR responding and body temperature, and impairment to cognitive performance was task specific. During chronic treatment, THC produced persistent residual impairment only to working memory; tolerance differentially developed to acute cognitive impairments. There was recovery from residual cognitive impairments to working memory within 2 weeks of abstinence. Compared with controls, D2/D3 receptor availability was not altered during chronic THC treatment. In conclusion, THC-induced disruptions in cognition were task-specific, as was tolerance development, and not related to changes in D2/D3 receptor availability. Intervention strategies for cannabis-use disorder that enhance working memory performance may facilitate positive treatment outcomes.

Perceived barriers for cannabis cessation: Relations to cannabis use problems, withdrawal symptoms, and self-efficacy for quitting

Cannabis is the most widely used illicit substance in the United States. Regular cannabis use appears to be a dynamic, chronic process consisting of multiple quit attempts, periods of reduction, periods of abstinence, and periods of continual use. Cannabis-related processes, including withdrawal, problematic consequences of use, and self-efficacy for quitting each contribute to the cycle of use and, in part, are maintained and reinforced by perceived barriers for cannabis cessation. Yet, no work has examined the association between perceived barriers for cannabis cessation and clinically-relevant processes related to cannabis use. To address this gap, the current study recruited a racially diverse sample (N=145, 63.4% Black or African American) of cannabis users from the community to test the hypothesis that greater perceived barriers for quitting cannabis was related to more cannabis use problems, more cannabis withdrawal symptoms, and lower self-efficacy for quitting cannabis. Structural equation modeling suggested that greater perceived barriers for quitting cannabis was uniquely associated with cannabis use problems (β=0.50, 95%CI [0.39, 0.65], p<0.001), greater withdrawal symptoms (β=0.39, 95%CI [0.30, 0.50], p<0.001), and lower self-efficacy for quitting (β=-0.17, 95%CI [-0.21, -0.02], p=0.028). The results of this study indicate perceived barriers for cannabis cessation may help in better understanding an array of clinically significant cannabis use processes. Indeed, the observed pattern of findings add to current theoretical models of substance use that aim to identify unique risk processes that may maintain substance use and provide valuable information that can be used to inform treatment for cannabis users.

ADHD and cannabis use in young adults examined using fMRI of a Go/NoGo task

Children diagnosed with attention-deficit/hyperactivity disorder (ADHD) are at increased risk for substance abuse. Response inhibition is a hallmark of ADHD, yet the combined effects of ADHD and regular substance use on neural networks associated with response inhibition are unknown. Task-based functional Magnetic Resonance Imaging (fMRI) data from young adults with childhood ADHD with (n = 25) and without (n = 25) cannabis use ≥ monthly in the past year were compared with a local normative comparison group (LNCG) with (n = 11) and without (n = 12) cannabis use. Go/NoGo behavioral and fMRI data were evaluated for main and interaction effects of ADHD diagnosis and cannabis use. ADHD participants made significantly more commission errors on NoGo trials than controls. ADHD participants also had less frontoparietal and frontostriatal activity, independent of cannabis use. No main effects of cannabis use on response inhibition or functional brain activation were observed. An interaction of ADHD diagnosis and cannabis use was found in the right hippocampus and cerebellar vermis, with increased recruitment of these regions in cannabis-using controls during correct response inhibition. ADHD participants had impaired response inhibition combined with less fronto-parietal/striatal activity, regardless of cannabis use history. Cannabis use did not impact behavioral response inhibition. Cannabis use was associated with hippocampal and cerebellar activation, areas rich in cannabinoid receptors, in LNCG but not ADHD participants. This may reflect recruitment of compensatory circuitry in cannabis using controls but not ADHD participants. Future studies targeting hippocampal and cerebellar-dependent function in these groups may provide further insight into how this circuitry is altered by ADHD and cannabis use.

Sex-related marijuana expectancies as predictors of sexual risk behavior following smoked marijuana challenge

Marijuana use has been associated with sexual risk behavior, but the mechanisms that underlie this relationship are not well understood. The present study examined whether marijuana acutely increased sexual risk on a behavioral decision-making task and whether sex-related marijuana outcome expectancies influenced sexual risk decisions after marijuana administration. Participants were heterosexual marijuana users (n = 126) who were randomly assigned to 1 of 4 study conditions using a 2 × 2 factorial design crossing drug administration (received 2.8% delta-9-tetrahydrocannabinol [THC] or 0% THC) with instructional set (told THC or told placebo). Participants completed a self-report measure of sex-related marijuana outcome expectancies at baseline and estimated likelihood of using condoms with a new and a steady partner in an interactive sexual role-play task (SRT) after smoking. In gender-specific analyses, there was a significant interaction of drug administration by sex-related outcome expectancies, such that for men in the received-placebo conditions, more salient sex-related marijuana outcome expectancies were associated with increased likelihood for sex without a condom with a new partner. Among women, there was no interaction or main effect of drug administration but more salient sex-related marijuana outcome expectancies were associated with increased likelihood of sex without a condom with a steady but not new partner. Findings suggest marijuana does not acutely increase risk for engaging in sexual risk behaviors. By contrast, sex-related marijuana outcome expectancies may play a more significant role in sexual decision-making process among marijuana users. (PsycINFO Database Record

Expectancy of impairment attenuates marijuana-induced risk taking

BACKGROUND

Marijuana use has been associated with increased risk-taking and impulsive behavior. While pharmacologic effects of marijuana can lead to inhibitory impairment, expectancy of potential impairment may result in compensatory behavioral response by decreasing impulsive decisions and risky behaviors. With the increases in marijuana use and related problems, a better understanding of the individual characteristics associated with marijuana intoxication and risky behavior is needed. This study examined the role of impairment expectancies in marijuana's acute effects on behavioral measures of impulsivity and risk-taking.

METHODS

Participants (N=136) were regular marijuana users. A balanced placebo design (BPD) was used crossing marijuana administration (i.e., 0% Tetrahydrocannabinol (THC) vs. 2.8% THC) with stimulus expectancy (i.e., Told Placebo vs. Told THC). Marijuana outcome expectancies were measured by self-report and dependent measures included a number of behavioral impulsivity tasks and the balloon analogue risk task (BART).

RESULTS

Among participants who received THC, higher expectancies for cognitive-behavioral impairment (CBI) were related to lower risk-taking on the BART. Among those who received placebo, there was no association between CBI expectancies and BART performance. CBI expectancies did not moderate the stimulus expectancy effect on the BART nor drug or stimulus expectancy effects on impulsivity measures.

CONCLUSIONS

Results provide initial evidence that expectancies of greater impairment are associated with compensatory behavior on a risk-taking task under acute marijuana intoxication. Future studies should examine the role of impairment expectancies on risk behaviors of substantial public health concern, such as driving while under the influence of marijuana.

Anxiety Sensitivity and Distress Intolerance as Predictors of Cannabis Dependence Symptoms, Problems, and Craving: The Mediating Role of Coping Motives

OBJECTIVE

The tendency to react with fear to anxiety-related sensations (anxiety sensitivity) and the inability to tolerate distressing psychological or physiological states (distress intolerance) are implicated in the comorbidity between affective psychopathology and cannabis use disorders. Emotionally vulnerable cannabis users may be particularly apt to use cannabis to cope with distress, which may both lead to and maintain its problematic use (e.g., dependence, craving). The current study tested a comprehensive model of anxiety sensitivity and distress intolerance as predictors of the number of cannabis dependence symptoms and problems, and severity of cannabis craving following deprivation from cannabis, and the mediating role of cannabis coping motives.

METHOD

Participants (n = 103; mean age = 21.2 years, SD = 4.3; 35.9% female) were non-treatment-seeking frequent cannabis users. Data were cross-sectional in nature. Anxiety sensitivity was assessed via self-report, and distress intolerance was assessed via both self-report and breath-holding duration.

RESULTS

Greater perceived distress intolerance, but not breath-holding duration or anxiety sensitivity, was associated with a greater number of cannabis dependence symptoms and problems and elevated cannabis craving. These relations were mediated by cannabis coping motives.

CONCLUSIONS

Findings provide specificity for the etiologic mechanisms related to emotional vulnerability and maintenance of cannabis problems. Perceived distress intolerance appears to be uniquely related to maladaptive coping motives for cannabis use, which could be meaningfully targeted in interventions for emotionally vulnerable cannabis users.

Cannabinoids in attention-deficit/hyperactivity disorder: A randomised-controlled trial

Adults with ADHD describe self-medicating with cannabis, with some reporting a preference for cannabis over ADHD medications. A small number of psychiatrists in the US prescribe cannabis medication for ADHD, despite there being no evidence from randomised controlled studies. The EMA-C trial (Experimental Medicine in ADHD-Cannabinoids) was a pilot randomised placebo-controlled experimental study of a cannabinoid medication, Sativex Oromucosal Spray, in 30 adults with ADHD. The primary outcome was cognitive performance and activity level using the QbTest. Secondary outcomes included ADHD and emotional lability (EL) symptoms. From 17.07.14 to 18.06.15, 30 participants were randomly assigned to the active (n=15) or placebo (n=15) group. For the primary outcome, no significant difference was found in the ITT analysis although the overall pattern of scores was such that the active group usually had scores that were better than the placebo group (Est=-0.17, 95%CI-0.40 to 0.07, p=0.16, n=15/11 active/placebo). For secondary outcomes Sativex was associated with a nominally significant improvement in hyperactivity/impulsivity (p=0.03) and a cognitive measure of inhibition (p=0.05), and a trend towards improvement for inattention (p=0.10) and EL (p=0.11). Per-protocol effects were higher. Results did not meet significance following adjustment for multiple testing. One serious (muscular seizures/spasms) and three mild adverse events occurred in the active group and one serious (cardiovascular problems) adverse event in the placebo group. Adults with ADHD may represent a subgroup of individuals who experience a reduction of symptoms and no cognitive impairments following cannabinoid use. While not definitive, this study provides preliminary evidence supporting the self-medication theory of cannabis use in ADHD and the need for further studies of the endocannabinoid system in ADHD.

Genetic and Modeling Approaches Reveal Distinct Components of Impulsive Behavior

Impulsivity is an endophenotype found in many psychiatric disorders including substance use disorders, pathological gambling, and attention deficit hyperactivity disorder. Two behavioral features often considered in impulsive behavior are behavioral inhibition (impulsive action) and delayed gratification (impulsive choice). However, the extent to which these behavioral constructs represent distinct facets of behavior with discrete biological bases is unclear. To test the hypothesis that impulsive action and impulsive choice represent statistically independent behavioral constructs in mice, we collected behavioral measures of impulsivity in a single cohort of mice using well-validated operant behavioral paradigms. Mice with manipulation of serotonin 1B receptor (5-HT_1BR) expression were included as a model of disordered impulsivity. A factor analysis was used to characterize correlations between the measures of impulsivity and to identify covariates. Using two approaches, we dissociated impulsive action from impulsive choice. First, the absence of 5-HT_1BRs caused increased impulsive action, but not impulsive choice. Second, based on an exploratory factor analysis, a two-factor model described the data well, with measures of impulsive action and choice separating into two independent factors. A multiple-indicator multiple-causes analysis showed that 5-HT_1BR expression and sex were significant covariates of impulsivity. Males displayed increased impulsivity in both dimensions, whereas 5-HT_1BR expression was a predictor of increased impulsive action only. These data support the conclusion that impulsive action and impulsive choice are distinct behavioral phenotypes with dissociable biological influences that can be modeled in mice. Our work may help inform better classification, diagnosis, and treatment of psychiatric disorders, which present with disordered impulsivity.

Seeing through the smoke: Human and animal studies of cannabis use and endocannabinoid signalling in corticolimbic networks

Public opinion surrounding the recreational use and therapeutic potential of cannabis is shifting. This review describes new work examining the behavioural and neural effects of cannabis and the endocannabinoid system, highlighting key regions within corticolimbic brain circuits. First, we consider the role of human genetic factors and cannabis strain chemotypic differences in contributing to interindividual variation in the response to cannabinoids, such as THC, and review studies demonstrating that THC-induced impairments in decision-making processes are mediated by actions at prefrontal CB1 receptors. We further describe evidence that signalling through prefrontal or ventral hippocampal CB1 receptors modulates mesolimbic dopamine activity, aberrations of which may contribute to emotional processing deficits in schizophrenia. Lastly, we review studies suggesting that endocannabinoid tone in the amygdala is a critical regulator of anxiety, and report new data showing that FAAH activity is integral to this response. Together, these findings underscore the importance of cannabinoid signalling in the regulation of cognitive and affective behaviours, and encourage further research given their social, political, and therapeutic implications.

Lateral Habenula Involvement in Impulsive Cocaine Seeking

The lateral habenula (LHb) is a brain structure receiving inputs from limbic forebrain areas and innervating major midbrain monoaminergic nuclei. Evidence indicates LHb involvement in sleep control, reward-based decision making, avoidance of punishment, and responses to stress. Additional work has established that the LHb mediates negative feedback in response to aversive events. As a hallmark of drug addiction is the inability to limit drug use despite negative consequences, we hypothesize that LHb dysfunction may have a role in the lack of control over drug seeking. Here we examine the effects of LHb inactivation in control over drug seeking in several cocaine self-administration (SA) paradigms in rats. We find that inhibition of the LHb with GABAergic agonists did not alter cocaine SA under progressive ratio or seeking/taking chained reinforcement schedules, or during punishment-induced suppression of cocaine-reinforced responding. In contrast, LHb inhibition increased cocaine seeking when the drug was not available in rats trained to discriminate its presence using an environmental cue. This effect of LHb inhibition was selective for cocaine, as it did not impair responding for sucrose reinforcement. The effect of LHb injection of GABA agonists was mimicked by intra-LHb muscarinic cholinergic (mACh) antagonist injection, and activation of mACh receptors excited a majority of LHb neurons in in vitro electrophysiology experiments. These results indicate that the LHb participates in the suppression of impulsive responding for cocaine through the activation of a cholinergic circuit, and they suggest that LHb dysfunction may contribute to impaired impulse control associated with drug addiction.

Anxiety sensitivity and cannabis use-related problems: The impact of race

BACKGROUND AND OBJECTIVES

Cannabis is the most widely used illicit substance among young adults. Anxiety sensitivity (AS; ie, fear of anxiety-related symptoms) is positively related to coping motives for cannabis use (which are robustly positively linked to cannabis-related problems). However, AS is unrelated to cannabis use-related problems. Yet, extant studies have been conducted on primarily White samples. It may be that among Black students, AS-physical concerns (ie, fear of physical anxiety-related sensations) are related to cannabis problems given that Black individuals are more likely than White individuals to report experiencing greater and more intense somatic symptoms when experiencing anxiety. Black individuals may rely on cannabis to cope with fear of these somatic symptoms, continuing to use despite cannabis-related problems.

METHODS

The current study tested whether race moderated the relation between AS-physical concerns and cannabis problems among 102 (85.3% female) current cannabis using undergraduates who were either non-Hispanic Black (n = 51) or non-Hispanic White (n = 51).

RESULTS

After controlling for frequency of cannabis use, income, and gender, race significantly moderated the relation between AS-physical concerns and cannabis use-related problems such that AS-physical concerns significantly predicted cannabis-related problems among Black and not White individuals.

DISCUSSION AND CONCLUSIONS

Findings highlight the importance of considering race in identifying psychosocial predictors of cannabis-related problems.

SCIENTIFIC SIGNIFICANCE

Intervention strategies for Black cannabis users may benefit from examining and targeting AS-physical concerns. (Am J Addict 2017;26:209-214).

Cognitive motor deficits in cannabis users

Cannabis use affects cortico-striatal networks that are essential for producing movement. In this review, we summarize the literature on motor system dysfunction in cannabis users and provide a rationale for why motor learning should be considered an important area in cannabis research. A majority of studies have addressed cognitive impairments in cannabis users and some have focused on driving performance, motor impulsivity, and motor inhibition. Our review of the literature has found that cannabis use is associated with motor performance impairments; however, there is a gap in the literature regarding impairments in motor learning. The involvement of the cortico-striatal network in both cannabis addiction and movement also suggests potential avenues for treatment and rehabilitation via the motor system.

Altered subjective reward valuation among female heavy marijuana users

Maladaptive decision-making is a cardinal feature of drug use, contributing to ongoing use, and reflecting alterations in how drug users assess uncertain reward value. Accumulating evidence indicates the consequences of heavy marijuana use are worse for female versus male animals and humans, but research assessing sex differences in reward-related decision-making among marijuana users remains scarce. We examined sex differences in the subjective valuation of certain and uncertain rewards among heavy marijuana users (52; 26 male and 26 female) and controls (52; 26 male and 26 female). We offered male and female heavy marijuana users and controls monetary rewards of certain and uncertain (probabilistic) values. We measured how preferences for uncertain rewards varied by the objective value of those rewards, moderators of reward uncertainty, Marijuana Group and Sex. Men were more sensitive to changes in the objective value of uncertain rewards than women. However, this effect of Sex differed by Marijuana Group. Female heavy marijuana users were more sensitive to changes in uncertain reward value, particularly when the "stakes" were high (i.e., greater difference between potential uncertain rewards), than female controls. Female heavy marijuana users' sensitivity to changes in the value of high stakes uncertain rewards was comparable to male marijuana users and controls. In contrast, male marijuana users' sensitivity to changes in the value of high stakes uncertain rewards did not differ from male controls. These results suggest sex differences in sensitivity to high risk rewards may be one pathway contributing to severer consequences of heavy marijuana use among women. (PsycINFO Database Record

Effects of various cannabinoid ligands on choice behaviour in a rat model of gambling

It is estimated that 0.6-1% of the population in the USA and Canada fulfil the Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM-5) criteria for gambling disorders (GD). To date, there are no approved pharmacological treatments for GD. The rat gambling task (rGT) is a recently developed rodent analogue of the Iowa gambling task in which rats are trained to associate four response holes with different magnitudes and probabilities of food pellet rewards and punishing time-out periods. Similar to healthy human volunteers, most rats adopt the optimal strategies (optimal group). However, a subset of animals show preference for the disadvantageous options (suboptimal group), mimicking the choice pattern of patients with GD. Here, we explored for the first time the effects of various cannabinoid ligands (WIN 55,212-2, AM 4113, AM 630 and URB 597) on the rGT. Administration of the cannabinoid agonist CB1/CB2 WIN 55,212-2 improved choice strategy and increased choice latency in the suboptimal group, but only increased perseverative behaviour, when punished, in the optimal group. Blockade of CB1 or CB2 receptors or inhibition of fatty-acid amide hydrolase did not affect rGT performance. These results suggest that stimulation of cannabinoid receptors could affect gambling choice behaviours differentially in some subgroups of subjects.

Interrelationships between marijuana demand and discounting of delayed rewards: Convergence in behavioral economic methods

BACKGROUND

Distinct behavioral economic domains, including high perceived drug value (demand) and delay discounting (DD), have been implicated in the initiation of drug use and the progression to dependence. However, it is unclear whether frequent marijuana users conform to a "reinforcer pathology" addiction model wherein marijuana demand and DD jointly increase risk for problematic marijuana use and cannabis dependence (CD).

METHODS

Participants (n=88, 34% female, 14% cannabis dependent) completed a marijuana purchase task at baseline. A delay discounting task was completed following placebo marijuana cigarette (0% THC) administration during a separate experimental session.

RESULTS

Marijuana demand and DD were quantified using area under the curve (AUC). In multiple regression models, demand uniquely predicted frequency of marijuana use while DD did not. In contrast, DD uniquely predicted CD symptom count while demand did not. There were no significant interactions between demand and DD in either model.

CONCLUSIONS

These findings suggest that frequent marijuana users exhibit key constituents of the reinforcer pathology model: high marijuana demand and steep discounting of delayed rewards. However, demand and DD appear to be independent rather than synergistic risk factors for elevated marijuana use and risk for progression to CD. Findings also provide support for using AUC as a singular marijuana demand metric, particularly when also examining other behavioral economic constructs that apply similar statistical approaches, such as DD, to support analytic methodological convergence.

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

BACKGROUND

Evidence 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.

METHODS

Data 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.

RESULTS

Cannabis 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.

LIMITATIONS

Suicidality was assessed only in individuals reporting depressed mood and/or anhedonia.

CONCLUSIONS

Our 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.

Acute and chronic effects of cannabidiol on Δ⁹-tetrahydrocannabinol (Δ⁹-THC)-induced disruption in stop signal task performance

Recent clinical and preclinical research has suggested that cannabidiol (CBD) and Δ9-tetrahydrocannabinol (Δ9-THC) have interactive effects on measures of cognition; however, the nature of these interactions is not yet fully characterized. To address this, we investigated the effects of Δ9-THC and CBD independently and in combination with proposed therapeutic dose ratios of 1:1 and 1:3 Δ9-THC:CBD in adult rhesus monkeys (n = 6) performing a stop signal task (SST). Additionally, the development of tolerance to the effects of Δ9-THC on SST performance was evaluated by determining the effects of acutely administered Δ9-THC (0.1-3.2 mg/kg), during a 24-day chronic Δ9-THC treatment period with Δ9-THC alone or in combination with CBD. Results indicate that Δ9-THC (0.032-0.32 mg/kg) dose-dependently decreased go success but did not alter go reaction time (RT) or stop signal RT (SSRT); CBD (0.1-1.0 mg/kg) was without effect on all measures and, when coadministered in a 1:1 dose ratio, did not exacerbate or attenuate the effects of Δ9-THC. When coadministered in a 1:3 dose ratio, CBD (1.0 mg/kg) attenuated the disruptive effects of 0.32 mg/kg Δ9-THC but did not alter the effects of other Δ9-THC doses. Increases in ED50 values for the effects of Δ9-THC on SST performance were apparent during chronic Δ9-THC treatment, with little evidence for modification of changes in sensitivity by CBD. These results indicate that CBD, when combined with Δ9-THC in clinically available dose ratios, does not exacerbate and, under restricted conditions may even attenuate, Δ9-THC's behavioral effects. (PsycINFO Database Record

Sex Effects of Marijuana on Brain Structure and Function

Background

Tetrahydrocannabinol (Δ⁹-THC), the primary ingredient in marijuana, exerts its effects across several neurological and biological systems that interact with the endocrine system. Thus, differential effects of Δ⁹-THC are likely to exist based on sex and hormone levels.

Methods

We reviewed the existing literature to determine sex-based effects of Δ⁹-THC on neural structure and functioning.

Results

The literature demonstrates differences in male and female marijuana users on brain structure, reward processing, attention, motor coordination, and sensitivity to withdrawal. However, inconsistencies exist in the literature regarding how marijuana affects men and women differentially, and more work is needed to understand these mechanisms. While extant literature remains inconclusive, differentiation between male and female marijuana users is likely due to neurological sexual dimorphism and differential social factors at play during development and adulthood.

Conclusions

Sex has important implications for marijuana use and the development of cannabis use disorders and should be considered in the development of prevention and treatment strategies.

Delay and probability discounting by drug-dependent cocaine and marijuana users

RATIONALE

Steep discounting of delayed monetary rewards by substance-dependent individuals is well-established. Less is known, however, about discounting other kinds of outcomes, and very little is known about discounting by marijuana-dependent individuals.

OBJECTIVES

To determine how cocaine-dependent individuals and marijuana-dependent individuals discount various delayed and probabilistic outcomes, both positive and negative.

METHODS

Marijuana-dependent individuals, cocaine-dependent individuals, and controls performed delay and probability discounting tasks with various hypothetical outcomes.

RESULTS

The cocaine-dependent (but not the marijuana-dependent) group discounted delayed liquid rewards and monetary gains, but not delayed losses, more steeply than the control group. In contrast, the marijuana-dependent group (but not the cocaine-dependent group) discounted delayed monetary losses more steeply than controls. There were no group differences in discounting for any of the probabilistic outcomes. Factor analysis revealed a delayed gain factor, a probabilistic gain factor, and a delayed/probabilistic loss factor. The delayed gain factor scores for the cocaine-dependent group, but not the marijuana-dependent group, differed significantly from those of the control group. The groups did not differ in their probabilistic gain factor scores, and the marijuana-dependent group did not differ from the controls with respect to their loss factor scores.

CONCLUSIONS

These results are inconsistent with the idea that steep discounting of both gains and losses and both delayed and probabilistic outcomes reflects a general impulsivity trait, as well as with the idea that all drug-dependent individuals are steep discounters. Rather, differences in discounting appear to be related to both the type of outcome and the specific drug on which individuals are dependent.

Cannabinoid Modulation of Frontolimbic Activation and Connectivity During Volitional Regulation of Negative Affect

Behavioral and brain research indicates that administration of Δ(9)-tetrahydrocannabinol (THC) alters threat perception and enhances the suppression of conditioned fear responses via modulation of the frontolimbic circuit. No prior studies, however, have examined whether THC also affects volitional forms of emotion processing such as cognitive reappraisal. The aim of the current study was therefore to examine the effects of THC on frontolimbic activation and functional connectivity during cognitive reappraisal in a sample of healthy adults. The study was a randomized, double-blind, placebo-controlled, between-subject design and all participants ingested either an oral dose of synthetic THC (n=41) or placebo (n=37) before completion of an emotion regulation task during functional magnetic resonance imaging (fMRI). Functional connectivity was assessed using generalized psychophysiological interaction (gPPI) analyses. Results indicated that although there were no group differences in self-reported attenuation of negative affect during cognitive reappraisal, relative to placebo, THC increased amygdala activation and reduced amygdala and dorsolateral prefrontal cortex (dlPFC) functional coupling during cognitive reappraisal of emotionally negative pictures. This suggests that in addition to automatic emotional processes, THC affects frontolimbic functioning during cognitive reappraisal.

Neural and neurochemical basis of reinforcement-guided decision making

Decision making is an adaptive behavior that takes into account several internal and external input variables and leads to the choice of a course of action over other available and often competing alternatives. While it has been studied in diverse fields ranging from mathematics, economics, ecology, and ethology to psychology and neuroscience, recent cross talk among perspectives from different fields has yielded novel descriptions of decision processes. Reinforcement-guided decision making models are based on economic and reinforcement learning theories, and their focus is on the maximization of acquired benefit over a defined period of time. Studies based on reinforcement-guided decision making have implicated a large network of neural circuits across the brain. This network includes a wide range of cortical (e.g., orbitofrontal cortex and anterior cingulate cortex) and subcortical (e.g., nucleus accumbens and subthalamic nucleus) brain areas and uses several neurotransmitter systems (e.g., dopaminergic and serotonergic systems) to communicate and process decision-related information. This review discusses distinct as well as overlapping contributions of these networks and neurotransmitter systems to the processing of decision making. We end the review by touching on neural circuitry and neuromodulatory regulation of exploratory decision making.

Effects of amphetamine, morphine, and CP 55, 940 on Go/No-Go task performance in rhesus monkeys

In humans, impulsivity measured as false alarms in a Go/No-Go task is reportedly decreased by amphetamine and is not affected by oxycodone and delta(9)-tetrahydrocannabinol. To model these findings in animals, three rhesus monkeys were trained to perform a food-reinforced Go/No-Go task. In this task, amphetamine was found to decrease false alarms (i.e. responding during No-Go trials), but only at doses that also decreased hits (i.e. responding during Go trials). Morphine generally decreased hits but not false alarms. The cannabinoid receptor agonist CP 55, 940 decreased both false alarms and hits, but only at doses that also decreased the number of trials completed. Additional studies in animals and humans are necessary to delineate the conditions under which amphetamine and other psychoactive drugs affect impulsivity in Go/No-Go tasks.

Low Pretreatment Impulsivity and High Medication Adherence Increase the Odds of Abstinence in a Trial of N-Acetylcysteine in Adolescents with Cannabis Use Disorder

BACKGROUND

In light of recent progress toward pharmacologic interventions to treat adolescent cannabis use disorder, it is important to consider which adolescent characteristics may be associated with a favorable response to treatment. This study presents secondary analyses from a parent randomized controlled trial of N-acetylcysteine (NAC) in adolescents with cannabis use disorder. We hypothesized that high pretreatment impulsivity and medication non-adherence would be associated with reduced abstinence rates.

METHODS

Participants were treatment-seeking adolescents (N=115) who met criteria for cannabis use disorder and were assessed for pretreatment impulsivity. They received 1200 mg NAC or placebo orally twice daily for 8 weeks. An intent-to-treat analysis using a repeated-measures logistic regression model was used to relate pretreatment impulsivity (Barratt Impulsiveness Scale) and treatment group to abstinence rates, measured by urine cannabinoid tests. To explore mechanisms by which NAC may reduce cannabis use, relationships between impulsivity, adherence, and abstinence were assessed in a second statistical model using data from participants with recorded adherence and urine cannabinoid test results (n=54).

RESULTS

In the intent-to-treat analysis, low pretreatment impulsivity, NAC treatment, and negative baseline urine cannabinoid test results independently increased the odds of having negative urine cannabinoid tests during treatment (OR=2.1, 2.3, and 5.3 respectively). In the sample of participants with adherence data (n=54), adherence tripled the odds of abstinence. Notably, the effect of adherence on abstinence was only observed in the NAC treatment group. Lastly, although the highly impulsive participants had reduced rates of abstinence, highly impulsive individuals adherent to NAC treatment had increased abstinence rates compared to non-adherent individuals.

CONCLUSION

Low impulsivity, NAC treatment, medication adherence, and baseline negative cannabinoid testing were associated with increased rates of abstinence in adolescents seeking treatment for cannabis use disorder. Efforts to optimize pharmacotherapy adherence may be particularly crucial for highly impulsive individuals. Understanding and addressing factors, such as impulsivity and adherence, which may affect outcomes, may aid in the successful evaluation and development of potentially promising pharmacotherapies.

Does Marijuana Use Contribute to Intimate Partner Aggression? A Brief Review and Directions for Future Research

Marijuana users are more likely to perpetrate intimate partner aggression (IPA) than non-users, yet the mechanism responsible for this association is unknown. Recent studies considering the association between episodes of marijuana use and episodes of IPA have failed to find evidence consistent with an acute effect of marijuana. Research gaps are highlighted and a heuristic model of marijuana's potential effects on IPA is presented. Research priorities include consideration of mediating mechanisms, moderating variables at the individual and couple level, and examination of acute effects of marijuana using daily report and EMA designs.

Marijuana's acute effects on cognitive bias for affective and marijuana cues

Marijuana produces acute increases in positive subjective effects and decreased reactivity to negative affective stimuli, though may also acutely induce anxiety. Implicit attentional and evaluative processes may explicate marijuana's ability to acutely increase positive and negative emotions. This within-subjects study examined whether smoked marijuana with 2.7-3.0% delta-9-tetrahydrocannabinol (THC), relative to placebo, acutely changed attentional processing of rewarding and negative affective stimuli as well as marijuana-specific stimuli. On 2 separate days, regular marijuana users (N = 89) smoked placebo or active THC cigarette and completed subjective ratings of mood, intoxication, urge to smoke marijuana, and 2 experimental tasks: pleasantness rating (response latency and perceived pleasantness of affective and marijuana-related stimuli) and emotional Stroop (attentional bias to affective stimuli). On the pleasantness rating task, active marijuana increased response latency to negatively valenced and marijuana-related (vs. neutral) visual stimuli, beyond a general slowing of response. Active marijuana also increased pleasantness ratings of marijuana images, although to a lesser extent than placebo due to reduced marijuana urge after smoking. Overall, active marijuana did not acutely change processing of positive emotional stimuli. There was no evidence of attentional bias to affective word stimuli on the emotional Stroop task with the exception of attentional bias to positive word stimuli in the subgroup of marijuana users with cannabis dependence. Marijuana may increase allocation of attentional resources toward marijuana-specific and negatively valenced visual stimuli without altering processing of positively valenced stimuli. Marijuana-specific cues may be more attractive with higher levels of marijuana craving and less wanted with low craving levels.

Brain activation to negative stimuli mediates a relationship between adolescent marijuana use and later emotional functioning

This work investigated the impact of heavy marijuana use during adolescence on emotional functioning, as well as the brain functional mediators of this effect. Participants (n=40) were recruited from the Michigan Longitudinal Study (MLS). Data on marijuana use were collected prospectively beginning in childhood as part of the MLS. Participants were classified as heavy marijuana users (n=20) or controls with minimal marijuana use. Two facets of emotional functioning-negative emotionality and resiliency (a self-regulatory mechanism)-were assessed as part of the MLS at three time points: mean age 13.4, mean age 19.6, and mean age 23.1. Functional neuroimaging data during an emotion-arousal word task were collected at mean age 20.2. Negative emotionality decreased and resiliency increased across the three time points in controls but not heavy marijuana users. Compared with controls, heavy marijuana users had less activation to negative words in temporal, prefrontal, and occipital cortices, insula, and amygdala. Activation of dorsolateral prefrontal cortex to negative words mediated an association between marijuana group and later negative emotionality. Activation of the cuneus/lingual gyrus mediated an association between marijuana group and later resiliency. Results support growing evidence that heavy marijuana use during adolescence affects later emotional outcomes.

Persistent effects of chronic Δ9-THC exposure on motor impulsivity in rats

RATIONALE

In humans, long-term marijuana use is associated with impaired impulse control and attentional capacity, though it has been difficult to distinguish pre-existing cognitive deficits from possible consequences of prolonged marijuana exposure.

OBJECTIVE

To evaluate the effects of long-term exposure to Δ9-Tetrahydrocannabinol (Δ9-THC), the primary psychoactive constituent in marijuana, on indices of impulse control and attentional capacity using the rat 5-Choice Serial Reaction Time Task (5-CSRTT).

METHODS

Ten 14-day cycles of Δ9-THC dosing and 5-CSRTT testing were employed, each comprised of 5-day Δ9-THC dosing (0.3 or 3 mg/kg b.i.d.) and 5-CSRTT testing during the 9 days of drug abstinence. Subsequent 5-CSRTT testing continued during 5 weeks of protracted abstinence.

RESULTS

Dose-dependent increases in motor impulsivity (premature responses) and behavioral disinhibition (perseverative responses) emerged following 5 cycles of Δ9-THC exposure that persisted for the remaining dosing and testing cycles. Δ9-THC-related disruptions in motor impulsivity and behavioral inhibition were most pronounced during cognitively challenging 5-CSRTT sessions incorporating varying novel inter-trial intervals (ITIs), and these disruptions persisted for at least 5 weeks of Δ9-THC abstinence. Δ9-THC-related impairments in attentional capacity (response accuracy) were also evident during variable ITI challenge tests, though these attentional disruptions abated within 3 weeks of Δ9-THC abstinence.

CONCLUSIONS

These observations demonstrate that long-term intermittent exposure to clinically meaningful Δ9-THC doses induces persistent impairments in impulse control and attentional function. If present in humans, these disruptions may impact academic and professional performance.

Sex differences in self-report and behavioral measures of disinhibition predicting marijuana use across adolescence

Disinhibition has been consistently linked to substance use across development. Recent research suggests, however, that these relations may be influenced by both sex and measurement approach. The current study examined the moderating effect of sex on the association between behavioral and self-report measures of disinhibition and marijuana use across adolescence. Participants were 115 boys and 89 girls initially evaluated at Grade 8 using a laboratory behavioral assessment and self-report questionnaires of disinhibitory variables. Marijuana use was measured annually from Grades 9 through 12. Results suggest that boys and girls did not differ on either self-reported or behaviorally assessed levels of disinhibition, and that disinhibition measured using both approaches was associated with increases in marijuana use over time. There was a significant interaction between sex and disinhibition, suggesting that boys (but not girls) who self-reported elevations in disinhibition evidenced greater increases in marijuana use. The current findings add to a growing literature supporting the importance of using multiple methods to assess disinhibition and highlight the critical role of biological sex in understanding these relations.