Sex differences in associations between cannabis craving and neural responses to cannabis cues: Implications for treatment

Biological sex and hormonal contraceptive associations with drug cue reactivity in cannabis use disorder

Biological sex differences in Cannabis Use Disorder (CUD) progression, cannabis withdrawal severity, and pharmacotherapy response have been reported, suggesting that CUD mechanisms may differ by sex. Drug cue reactivity is an established predictor of drug use behavior, but the literature on sex differences in drug cue reactivity is mixed, including in CUD. One possible moderator of sex differences in drug cue reactivity is hormonal contraceptive (HC) use. The aim of the present study was to test whether sex differences in neural cannabis cue reactivity and craving varied by female HC use in a CUD sample. As part of a larger study, 152 adults reporting frequent cannabis use completed a drug cue reactivity task during electrocenphalogram recording. Late positive potential (LPP) amplitude modulation by cannabis cues was used to measure neural cue reactivity. Craving after the cue reactivity task was also assessed. Males (n = 74) and naturally-cycling females (n = 26), who did not differ from each other, showed significantly greater LPP enhancement to cannabis vs. neutral cues compared to HC-using females (n = 52), an effect mostly driven by neutral cues. Craving was significantly higher in naturally-cycling but not HC-using females compared to males, but only in covariate-unadjusted analyses. Exploratory analyses of HC and menstrual phase characteristics indicate a progesterone-related mechanism may underlie HC effects on cannabis cue reactivity. The present study's results suggest that mixed findings on drug cue reactivity sex differences may be due to variability in HC use, which has implications for sex-specific models of CUD progression and treatment.

Exploring the Utility of a Functional Magnetic Resonance Imaging (fMRI) Cannabis Cue-Reactivity Paradigm in Treatment Seeking Adults with Cannabis Use Disorder

Introduction

Functional magnetic resonance imaging (fMRI) studies examining cue-reactivity in cannabis use disorder (CUD) to date have either involved non-treatment seeking participants or been small. We addressed this gap by administering an fMRI cue-reactivity task to CUD participants entering two separate clinical trials.

Methods

Treatment-seeking participants with moderate or severe CUD had behavioral craving measured at baseline via the Marijuana Craving Questionnaire (MCQ-SF). They additionally completed a visual cannabis cue-reactivity paradigm during fMRI following 24-hours of abstinence from cannabis. During fMRI, the Blood Oxygen Level Dependent (BOLD) signal was acquired while participants viewed cannabis-images or matched-neutral-images. BOLD responses were correlated with the MCQ-SF using a General Linear Model.

Results

N=65 participants (32% female; mean age 30.4±9.9SD) averaged 46.3±15.5SD on the MCQ-SF. When contrasting cannabis-images vs. matched-neutral-images, participants showed greater BOLD response in bilateral ventromedial prefrontal, dorsolateral prefrontal, anterior cingulate, and visual cortices, as well as the striatum. Similarly, there was stronger task-based functional-connectivity (tbFC) between the medial prefrontal cortex and both the amygdala and the visual cortex. There were no significant differences in either activation or tbFC between studies or between sexes. Craving negatively correlated with BOLD response in the left ventral striatum (R 2 =-0.25; p =0.01).

Conclusions

We found that, among two separate treatment-seeking CUD groups, cannabis cue-reactivity was evidenced by greater activation and tbFC in regions related to executive function and reward processing, and craving was negatively associated with cue-reactivity in the ventral striatum. Future directions include examining if pharmacological, neuromodulatory, or psychosocial interventions can alter corticostriatal cue-reactivity.

Interaction of gonadal hormones, dopaminergic system, and epigenetic regulation in the generation of sex differences in substance use disorders: A systematic review

Substance use disorder (SUD) is a chronic condition characterized by pathological drug-taking and seeking behaviors. Remarkably different between males and females, suggesting that drug addiction is a sexually differentiated disorder. The neurobiological bases of sex differences in SUD include sex-specific reward system activation, influenced by interactions between gonadal hormone level changes, dopaminergic reward circuits, and epigenetic modifications of key reward system genes. This systematic review, adhering to PICOS and PRISMA-P 2015 guidelines, highlights the sex-dependent roles of estrogens, progesterone, and testosterone in SUD. In particular, estradiol elevates and progesterone reduces dopaminergic activity in SUD females, whilst testosterone and progesterone augment SUD behavior in males. Finally, SUD is associated with a sex-specific increase in the rate of opioid and monoaminergic gene methylation. The study reveals the need for detailed research on gonadal hormone levels, dopaminergic or reward system activity, and epigenetic landscapes in both sexes for efficient SUD therapy development.

Sex differences in acute delta-9-tetrahydrocannabinol (Δ9-THC) response and tolerance as a function of mouse strain

Cannabinoids are increasingly used to alleviate pain; however, tolerance to their antinociceptive effects, including those of delta-9-tetrahydrocannabinol (Δ9-THC), may limit their therapeutic utility. With more women than men using medical cannabis for pain relief, it is crucial to understand how sex influences cannabinoid-mediated antinociception and tolerance. Though studies in rats consistently find females are more sensitive to the acute antinociceptive effects of cannabinoids, our work with mice consistently finds the converse. The present study examined whether our observed sex differences in Δ9-THC-induced antinociception and tolerance are consistent across multiple mouse strains or are strain-dependent. Male and female C57BL/6J (B6), DBA/2, AKR, and CBA/J mice were assessed for differences in acute Δ9-THC-induced antinociception and hypothermia prior to and following seven days of once-daily Δ9-THC administration. Consistent with our previous findings, male B6 mice were more sensitive to the acute antinociceptive effects of Δ9-THC than female littermates, an effect which dissipated with age. B6 males had decreased cannabinoid expression in the PAG compared to females. While DBA and CBA female mice showed increased Δ9-THC-antinociception compared to male littermates at 30 and 10 mg/kg Δ9-THC, respectively, these differences were less pronounced at higher doses, revealing that dose of Δ9-THC may also be important. Overall, CBA mice were more sensitive to Δ9-THC-induced antinociception while AKR mice were less responsive. These studies highlight the therapeutic potential of Δ9-THC in pain management and underscore the importance of considering not only Δ9-THC dose as a function of sex, but potentially genetic differences when evaluating their clinical utility.

Mechanisms of cannabinoid tolerance

Cannabis has been used recreationally and medically for centuries, yet research into understanding the mechanisms of its therapeutic effects has only recently garnered more attention. There is evidence to support the use of cannabinoids for the treatment of chronic pain, muscle spasticity, nausea and vomiting due to chemotherapy, improving weight gain in HIV-related cachexia, emesis, sleep disorders, managing symptoms in Tourette syndrome, and patient-reported muscle spasticity from multiple sclerosis. However, tolerance and the risk for cannabis use disorder are two significant disadvantages for cannabinoid-based therapies in humans. Recent work has revealed prominent sex differences in the acute response and tolerance to cannabinoids in both humans and animal models. This review will discuss evidence demonstrating cannabinoid tolerance in rodents, non-human primates, and humans and our current understanding of the neuroadaptations occurring at the cannabinoid type 1 receptor (CB1R) that are responsible tolerance. CB1R expression is downregulated in tolerant animals and humans while there is strong evidence of CB1R desensitization in cannabinoid tolerant rodent models. Throughout the review, critical knowledge gaps are indicated and discussed, such as the lack of a neuroimaging probe to assess CB1R desensitization in humans. The review discusses the intracellular signaling pathways that are responsible for mediating CB1R desensitization and downregulation including the action of G protein-coupled receptor kinases, β-arrestin2 recruitment, c-Jun N-terminal kinases, protein kinase A, and the intracellular trafficking of CB1R. Finally, the review discusses approaches to reduce cannabinoid tolerance in humans based on our current understanding of the neuroadaptations and mechanisms responsible for this process.

Sex-specific mechanisms of tolerance for the cannabinoid agonists CP55,940 and delta-9-tetrahydrocannabinol (Δ9-THC)

RATIONALE

Tolerance to cannabinoids could limit their therapeutic potential. Male mice expressing a desensitization-resistant form (S426A/S430A) of the type-1 cannabinoid receptor (CB₁R) show delayed tolerance to delta-9-tetrahydrocannabinol (∆⁹-THC) but not CP55,940. With more women than men using medical cannabis for pain relief, it is essential to understand sex differences in cannabinoid antinociception, hypothermia, and resultant tolerance.

OBJECTIVE

Our objective was to determine whether female mice rely on the same molecular mechanisms for tolerance to the antinociceptive and/or hypothermic effects of cannabinoids that we have previously reported in males. We determined whether the S426A/S430A mutation differentially disrupts antinociceptive and/or hypothermic tolerance to CP55,940 and/or Δ⁹-THC in male and female S426A/S430A mutant and wild-type littermates.

RESULTS

The S426A/S430A mutation conferred an enhanced antinociceptive response for ∆⁹-THC and CP55,940 in both male and female mice. While the S426A/S430A mutation conferred partial resistance to ∆⁹-THC tolerance in male mice, disruption of CB₁R desensitization had no effect on tolerance to ∆⁹-THC in female mice. The mutation did not alter tolerance to the hypothermic effects of ∆⁹-THC or CP55,940 in either sex. Interestingly, female mice were markedly less sensitive to the antinociceptive effects of 30 mg/kg ∆⁹-THC and 0.3 mg/kg CP55,940 compared with male mice.

CONCLUSIONS

Our results suggest that disruption of the GRK/βarrestin2 pathway of desensitization alters tolerance to Δ⁹-THC but not CP55,940 in male but not female mice. As tolerance to Δ⁹-THC appears to develop differently in males and females, sex should be considered when assessing the therapeutic potential and dependence liability of cannabinoids.

Sex and dependence related neuroanatomical differences in regular cannabis users: findings from the ENIGMA Addiction Working Group

Males and females show different patterns of cannabis use and related psychosocial outcomes. However, the neuroanatomical substrates underlying such differences are poorly understood. The aim of this study was to map sex differences in the neurobiology (as indexed by brain volumes) of dependent and recreational cannabis use. We compared the volume of a priori regions of interest (i.e., amygdala, hippocampus, nucleus accumbens, insula, orbitofrontal cortex (OFC), anterior cingulate cortex and cerebellum) between 129 regular cannabis users (of whom 70 were recreational users and 59 cannabis dependent) and 114 controls recruited from the ENIGMA Addiction Working Group, accounting for intracranial volume, age, IQ, and alcohol and tobacco use. Dependent cannabis users, particularly females, had (marginally significant) smaller volumes of the lateral OFC and cerebellar white matter than recreational users and controls. In dependent (but not recreational) cannabis users, there was a significant association between female sex and smaller volumes of the cerebellar white matter and OFC. Volume of the OFC was also predicted by monthly standard drinks. No significant effects emerged the other brain regions of interest. Our findings warrant future multimodal studies that examine if sex and cannabis dependence are specific key drivers of neurobiological alterations in cannabis users. This, in turn, could help to identify neural pathways specifically involved in vulnerable cannabis users (e.g., females with cannabis dependence) and inform individually tailored neurobiological targets for treatment.

Patterns of brain function associated with cannabis cue-reactivity in regular cannabis users: a systematic review of fMRI studies

RATIONALE

Regular cannabis use (i.e. ≥ monthly) is highly prevalent, with past year use being reported by ~ 200 million people globally.High reactivity to cannabis cues is a key feature of regular cannabis use and has been ascribed to greater cannabis exposure and craving, but the underlying neurobiology is yet to be systematically integrated.

OBJECTIVES

We aim to systematically summarise the findings from fMRI studies which examined brain function in cannabis users while exposed to cannabis vs neutral stimuli during a cue-reactivity fMRI task.

METHODS

A systematic search of PsycINFO, PubMed and Scopus databases was pre-registered in PROSPERO (CRD42020171750) and conducted following PRISMA guidelines. Eighteen studies met inclusion/exclusion criteria. Samples comprised 918 participants (340 female) aged 16-38 years. Of these, 603 were regular cannabis users, and 315 were controls.

RESULTS

The literature consistently reported greater brain activity in cannabis users while exposed to cannabis vs neutral stimuli in three key brain areas: the striatum, the prefrontal (anterior cingulate, middle frontal) and the parietal cortex (posterior cingulate/precuneus) and additional brain regions (hippocampus, amygdala, thalamus, occipital cortex). Preliminary correlations emerged between cannabis craving and the function of partially overlapping regions (amygdala, striatum, orbitofrontal cortex ).

CONCLUSIONS

Exposure to cannabis-cues may elicit greater brain function and thus trigger cravings in regular cannabis users and thus trigger cannabis craving. Standardised and longitudinal assessments of cannabis use and related problems are required to profile with greater precision the neurobiology of cannabis cue-reactivity, and its role in predicting  cravings and relapse.

Independent and Combined Effects of Nicotine or Chronic Tobacco Smoking and HIV on the Brain: A Review of Preclinical and Clinical Studies

Tobacco smoking is highly prevalent among HIV-infected individuals. Chronic smokers with HIV showed greater cognitive deficits and impulsivity, and had more psychopathological symptoms and greater neuroinflammation than HIV non-smokers or smokers without HIV infection. However, preclinical studies that evaluated the combined effects of HIV-infection and tobacco smoking are scare. The preclinical models typically used cell cultures or animal models that involved specific HIV viral proteins or the administration of nicotine to rodents. These preclinical models consistently demonstrated that nicotine had neuroprotective and anti-inflammatory effects, leading to cognitive enhancement. Although the major addictive ingredient in tobacco smoking is nicotine, chronic smoking does not lead to improved cognitive function in humans. Therefore, preclinical studies designed to unravel the interactive effects of chronic tobacco smoking and HIV infection are needed. In this review, we summarized the preclinical studies that demonstrated the neuroprotective effects of nicotine, the neurotoxic effects of the HIV viral proteins, and the scant literature on nicotine or tobacco smoke in HIV transgenic rat models. We also reviewed the clinical studies that evaluated the neurotoxic effects of tobacco smoking, HIV infection and their combined effects on the brain, including studies that evaluated the cognitive and behavioral assessments, as well as neuroimaging measures. Lastly, we compared the different approaches between preclinical and clinical studies, identified some gaps and proposed some future directions. Graphical abstract Independent and combined effects of HIV and tobacco/nicotine. Left top and bottom panels: Both clinical studies of HIV infected persons and preclinical studies using viral proteins in vitro or in vivo in animal models showed that HIV infection could lead to neurotoxicity and neuroinflammation. Right top and bottom panels: While clinical studies of tobacco smoking consistently showed deleterious effects of smoking, clinical and preclinical studies that used nicotine show mild cognitive enhancement, neuroprotective and possibly anti-inflammatory effects. In the developing brain, however, nicotine is neurotoxic. Middle overlapping panels: Clinical studies of persons with HIV who were smokers typically showed additive deleterious effects of HIV and tobacco smoking. However, in the preclinical studies, when nicotine was administered to the HIV-1 Tg rats, the neurotoxic effects of HIV were attenuated, but tobacco smoke worsened the inflammatory cascade.

Baclofen-induced Changes in the Resting Brain Modulate Smoking Cue Reactivity: A Double-blind Placebo-controlled Functional Magnetic Resonance Imaging Study in Cigarette Smokers

Objective

Smoking cue-(SC) elicited craving can lead to relapse in SC-vulnerable individuals. Thus, identifying treatments that target SC-elicited craving is a top research priority. Reduced drug cue neural activity is associated with recovery and is marked by a profile of greater tonic (resting) activation in executive control regions, and increased connectivity between executive and salience regions. Evidence suggests the GABA-B agonist baclofen can reduce drug cue-elicited neural activity, potentially through its actions on the resting brain. Based on the literature, we hypothesize that baclofen’s effects in the resting brain can predict its effects during SC exposure.

Methods

In this longitudinal, double blind, placebo-controlled neuropharmacological study 43 non-abstinent, sated treatment-seeking cigarette smokers (63% male) participated in an fMRI resting-state scan and a SC-reactivity task prior to (T1) and 3 weeks following randomization (T2; baclofen: 80 mg/day; n = 21). Subjective craving reports were acquired before and after SC exposure to explicitly examine SC-induced craving.

Results

Whole-brain full-factorial analysis revealed a group-by-time interaction with greater resting brain activation of the right dorsolateral prefrontal cortex (dlPFC) at T2 in the baclofen group (BAC) (p_FWEcorr = 0.02), which was associated with reduced neural responses to SCs in key cue-reactive brain regions; the anterior ventral insula and ventromedial prefrontal cortex (p_FWEcorr < 0.01). BAC, but not the placebo group reported decreased SC-elicited craving (p = 0.02).

Conclusion

Results suggest that baclofen mitigates the reward response to SCs through an increase in tonic activation of the dlPFC, an executive control region. Through these mechanisms, baclofen may offer SC-vulnerable smokers protection from SC-induced relapse.

Sex-related differences in subjective, but not neural, cue-elicited craving response in heavy cannabis users

BACKGROUND

Studies indicate that female cannabis users progress through the milestones of cannabis use disorder (CUD) more quickly than male users, likely due to greater subjective craving response in women relative to men. While studies have reported sex-related differences in subjective craving, differences in neural response and the relative contributions of neural and behavioral response remain unclear.

METHODS

We examined sex-related differences in neural and behavioral response to cannabis cues and cannabis use measures in 112 heavy cannabis users (54 females). We used principal component analysis to determine the relative contributions of neural and behavioral response and cannabis use measures.

RESULTS

We found that principal component (PC) 1, which accounts for the most variance in the dataset, was correlated with neural response to cannabis cues with no differences between male and female users (p = 0.21). PC2, which accounts for the second-most variance, was correlated with subjective craving such that female users exhibited greater subjective craving relative to male users (p = 0.003). We also found that CUD symptoms correlated with both PC1 and PC2, corroborating the relationship between craving and CUD severity.

CONCLUSIONS

These results indicate that neural activity primarily underlies response to cannabis cues and that a complex relationship characterizes a convergent neural response and a divergent subjective craving response that differs between the sexes. Accounting for these differences will increase efficacy of treatments through personalized approaches.

Brain activation to cannabis- and alcohol-related words in alcohol use disorder

Cannabis abuse commonly co-occurs with alcohol use disorder (AUD). With increased acceptance and accessibility to cannabis in the US, it is imperative to understand the psychological and neural mechanisms of concurrent alcohol and cannabis use. We hypothesized that neural alcohol-cue conditioning may extent to other drug-related stimuli, such as cannabis, and underwrite the loss of control over reward-driven behavior. Task-activated fMRI examined the neural correlates of alcohol- and cannabis-related word cues in 21 abstinent AUD and 18 control subjects. Relative to controls, AUD showed behavioral attentional biases and frontal hypoactivation to both alcohol- and cannabis-related words. This cue-elicited prefrontal hypoactivation was related to higher lifetime alcohol consumption (pcorrected < 0.02) and modulated by past cannabis use histories (p ≦ 0.001). In particular, frontal hypoactivation to both alcohol and cannabis cues was pronounced in AUD without prior cannabis exposure. Overall, frontal control mechanisms in abstinent AUD were not sufficiently engaged to override automatic alcohol and cannabis-related intrusions, enhancing the risk for relapse and potentially for alcohol and cannabis co-use with the increased social acceptance and accessibility in the US.

Reward, Control & Decision-Making in Cannabis Use Disorder: Insights from Functional MRI

The recreational consumption of cannabis has increased significantly across the world with an estimated 180 million people currently using. In the United States, 4.1 million are currently diagnosed with cannabis use disorder. Cannabis dependence and abuse was combined into a single entity as a behavioral disorder with a problematic pattern of cannabis use and termed cannabis use disorder by the Diagnostic and Statistical Manual of Mental Disorders. Chronic use of cannabis has been linked with region-specific effects across the brain mediating reward processing, cognitive control and decision-making that are central to understanding addictive behaviors. This review presents a snapshot of the current literature assessing the effects of chronic cannabis use on human brain function via functional MRI. Studies employing various paradigms and contrasting cognitive activation amongst cannabis users and non-users were incorporated. The effects of trans-del-ta-9-tetrahydrocannabinol (Δ9-THC) in marijuana and other preparations of cannabis are mediated by the endocannabinoid system, which is also briefly introduced.Much variation exists in the current literature regarding the functional changes associated with chronic cannabis use. One possible explanation for this variation is the heterogeneity in study designs, with little implementation of standardized diagnostic criteria when selecting chronic users, distinct time points of participant assessment, differing cognitive paradigms and imaging protocols. As such, there is an urgent requirement for future investigations that further characterize functional changes associated with chronic cannabis use.

Approach bias modification for cannabis use disorder: A proof-of-principle study

BACKGROUND

More effective treatments for cannabis use disorder (CUD) are needed. Evidence suggests that biases in cognitive processing of drug-related stimuli are central to the development and maintenance of addiction. The current study examined the feasibility and effect of a novel intervention - approach bias modification (ApBM) - on cannabis approach bias and cue-reactivity.

METHODS

A randomized, double-blind, sham-controlled proof-of-principle laboratory experiment investigated the effect of a four-session computerized ApBM training protocol on cannabis approach bias and cue-reactivity in non-treatment seeking adults age 18-65 with CUD (N = 33). ApBM procedures involved responding to cannabis or neutral stimuli using a computer joystick to model approach or avoidance behavior. Reactivity to tactile, olfactory, and auditory cue sets was assessed with physiological (blood pressure and heart rate) and subjective (cannabis craving) measures. Cannabis use was assessed via self-report.

RESULTS

Participants receiving ApBM showed blunted cannabis cue-induced craving at the end of training compared to those in the sham-ApBM condition (p = .05). A preliminary gender effect on cannabis use was also found; men receiving ApBM reported fewer cannabis use sessions per day at the end of training compared to women (p = .02), while there were no differences between men and women in the sham condition. ApBM did not attenuate cannabis approach bias following training.

CONCLUSION

Preliminary results indicate that ApBM may be efficacious in reducing cannabis cue-reactivity and improving cannabis use outcomes. While encouraging, the results should be interpreted with caution. Investigation of ApBM as an adjunct to psychosocial treatments for treatment-seeking adults with CUD is warranted.

Mechanisms Underlying Sex Differences in Cannabis Use

Purpose of the Review

Cannabis is the most commonly used illicit substance worldwide. In recent decades, highly concentrated products have flooded the market, and prevalence rates have increased. Gender differences exist in cannabis use, as men have higher prevalence of both cannabis use and cannabis use disorder (CUD), while women progress more rapidly from first use to CUD. This paper reviews findings from preclinical and human studies examining the sex-specific neurobiological underpinnings of cannabis use and CUD, and associations with psychiatric symptoms.

Recent Findings

Sex differences exist in the endocannabinoid system, in cannabis exposure effects on brain structure and function, and in the co-occurrence of cannabis use with symptoms of anxiety, depression and schizophrenia. In female cannabis users, anxiety symptoms correlate with larger amygdala volume and social anxiety disorder symptoms correlate with CUD symptoms. Female cannabis users are reported to be especially vulnerable to earlier onset of schizophrenia, and mixed trends emerge in the correlation of depressive symptoms with cannabis exposure in females and males.

Summary

As prevalence of cannabis use may continue to increase given the shifting policy landscape regarding marijuana laws, understanding the neurobiological mechanisms of cannabis exposure in females and males is key. Examining these mechanisms may help inform future research on sex-specific pharmacological and behavioral interventions for women and men with high-risk cannabis use, comorbid psychiatric disease, and CUD.

Sex as a biological variable: Drug use and abuse

The study of sex as a biological variable is a necessary emphasis across a wide array of endpoints, including basic neuroscience, medicine, mental health, physiology and behavior. The present review summarizes work from clinical and preclinical populations on sex differences in drug use and abuse, ranging from initiation to escalation/dysregulation and from drug cessation/abstinence to relapse. These differences are analyzed in the context of the addiction cycle conceptualization of Koob and his colleagues and address patterns of drug use (binge/intoxication), motivation underlying its use (withdrawal/negative affect) and likelihood and causes of craving and relapse of drug taking (preoccupation/anticipation). Following this overview, an assessment of the basis for the reported sex differences is discussed in the context of the affective (rewarding and aversive) properties of drugs of abuse and how such properties and their balance vary with sex and contribute to drug intake. Finally, the interaction of sex with several experiential (drug history) and subject (age) factors and how these interactions affect reward and aversion are discussed to highlight the importance of understanding such interactions in predicting drug use and abuse. We note that sex as a biological variable remains one of critical evaluation and that such investigations of sex differences in drug use and abuse continue and be expanded to assess all facets of their mediation, including these affective properties, how their balance may be impacted by the multiple conditions under which drugs are taken and how this overall balance affects drug use and addiction vulnerability.

Multi-site exploration of sex differences in brain reactivity to smoking cues: Consensus across sites and methodologies

BACKGROUND

Biological sex influences cigarette smoking behavior. More men than women smoke, but women have a harder time quitting. Sex differences in smoking cue (SC) reactivity may underlie such behavioral differences. However, the influence of sex on brain reactivity to SCs has yielded inconsistent findings suggesting the need for continued study. Here, we investigated the effect of sex on SC reactivity across two sites using different imaging modalities and SC stimulus types.

METHODS

Pseudo-continuous arterial spin-labeled (pCASL) perfusion functional magnetic resonance imaging (fMRI) was used to assess brain responses to SC versus non-SC videos in 40 smokers (23 females) at the University of Pennsylvania. BOLD fMRI was used to assess brain responses to SC versus non-SC still images in 32 smokers (18 females) at McLean Hospital. Brain reactivity to SCs was compared between men and women and was correlated with SC-induced craving.

RESULTS

In both cohorts, males showed higher SC versus non-SC reactivity compared to females in reward-related brain regions (i.e., ventral striatum/ventral pallidum, ventral medial prefrontal cortex). Brain activation during SC versus non-SC exposure correlated positively with SC-induced subjective craving in males, but not females.

CONCLUSIONS

The current work provides much needed replication and validation of sex differences in SC-reactivity. These findings also add to a body of literature showing that men have greater reward-related brain activation to drug cues across drug classes. Such sex differences confirm the need to consider sex not only when evaluating SC-reactivity but when examining nicotine dependence etiology and treatment.

Cannabis use, COMT, BDNF and age at first-episode psychosis

Although an interaction between COMT Val158Met and BDNF Val66Met polymorphisms with cannabis use has been proposed with respect to the risk of psychosis emergence, findings remain inconclusive. The aim of the present study was to evaluate the different possible associations between these polymorphisms and early cannabis use and the age at the first episode of psychosis. The relationship between age at psychosis onset and COMT Val158Met and BDNF Val66Met polymorphisms with early cannabis use as well as those factors associated with early cannabis use were investigated. Among 260 Caucasian first-episode psychosis patients, early cannabis use and the presence of the met-allele from the BDNF Val66Met polymorphism were significantly associated with age at psychosis onset. Furthermore, early cannabis use was significantly associated with male gender in the logistic regression analysis. These findings provide evidence of the important role of early cannabis use and the Val66Met BDNF polymorphism on age at psychosis onset and they point out to sex-specific differences in cannabis use patterns.

Sex differences in impulsive and compulsive behaviors: a focus on drug addiction

Sex differences in inhibition and self-regulation at a behavioral level have been widely described. From an evolutionary point of view, the different selection pressures placed on male and female hominids led them to differ in their behavioral strategies that allowed our species to survive during natural selection processes. These differences reflect changes in neural and structural plasticity that might be the core of sex differences, and of the susceptibility towards one psychiatric condition rather than another. The goal of the present review is to summarize current evidence for such a dichotomy in impulsive and compulsive behavior with a focus on drug addiction. Sex-dependent differences in drug abuse and dependence will be examined in the context of pathophysiological regulation of impulse and motivation by neuromodulators (i.e. gonadal hormones) and neurotransmitters (i.e. dopamine). Advances in the understanding of the sex differences in the capability to control impulses and motivational states is key for the determination of efficacious biologically based intervention and prevention strategies for several neuropsychiatric disorders where loss of impulse control and compulsivity are the core symptoms.

Gender differences in cannabis use disorder treatment: Change readiness and taking steps predict worse cannabis outcomes for women

INTRODUCTION

Gender differences in cannabis use and cannabis use disorder have been established. Regarding treatment, some evidence suggests that women are less responsive, though the mechanisms are not well understood. Motivation to change and self-efficacy are associated with better outcomes overall, and may help explain gender differences in cannabis use outcomes.

METHODS

A secondary data analysis of a double-blind placebo controlled trial of buspirone treatment for cannabis dependence (N=175) was conducted. Self-report assessments of motivation to change, self-efficacy, and other clinical correlates were completed at baseline, and cannabis use was measured throughout the study.

RESULTS

There was a significant interaction between gender and taking steps on abstinence. Counter to hypothesis, higher taking steps reduced likelihood of achieving abstinence among women; there was no association among men. Subsequently, taking steps was associated with self-efficacy and quantity of use among men, and cannabis related problems among women. There was a significant interaction between gender and readiness to change on creatinine adjusted cannabinoid levels. Change readiness was positively associated with cannabinoid levels among women, but not men.

CONCLUSIONS

Motivation to change and initiation of change behavior predict worse cannabis outcomes in women. Men and women differ in what motivates change behavior. Social desirability, neurobiology, and treatment type may impact these effects. Gender differences in cannabis use and treatment responsiveness must be considered in future studies.

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.

Early Versus Late Onset of Cannabis Use: Differences in Striatal Response to Cannabis Cues

Addiction theories posit that addiction is the result of a progressive transition from voluntary to habitual, compulsive drug use—changes that have been linked, in animals, to a shift from ventral to dorsal striatal control over drug-seeking behavior. Thus, we hypothesized that early-onset (EOs) cannabis users versus late-onset (LOs) cannabis users might exhibit, respectively, greater dorsal versus ventral striatal response to drug cues. We used functional magnetic resonance imaging and an event-related blood oxygen level-dependent backward-masking task to evaluate striatal responses to backward-masked cannabis cues (vs. neutral cues) in EOs (<16 years old, n=15) and LOs (≥16 years old, n=26) with similar recent cannabis use patterns. Direct comparisons revealed that EOs showed greater response to cannabis cues in the dorsal striatum than LOs (p<0.01, k>50 voxels). Within-group analyses revealed that EOs showed greater neural response to cannabis cues in the dorsal striatum, whereas LOs exhibited greater neural response to cannabis cues in the ventral striatum. Although cross-sectional, these findings are consistent with recent addiction theories suggesting a progressive shift from ventral to dorsal striatal control over drug-seeking behavior and highlight the importance of age of onset of cannabis use on the brain and cognition.