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Coelho SG, Hendershot CS, Aston ER, Ruocco AC, Quilty LC, Tyndale RF, Wardell JD. Executive functions and behavioral economic demand for cannabis among young adults: Indirect associations with cannabis consumption and cannabis use disorder. Exp Clin Psychopharmacol 2024; 32:305-315. [PMID: 37732960 PMCID: PMC10954585 DOI: 10.1037/pha0000678] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 09/22/2023]
Abstract
Behavioral economic demand for cannabis is robustly associated with cannabis consumption and cannabis use disorder (CUD). However, few studies have examined the processes underlying individual differences in the relative valuation of cannabis (i.e., demand). This study examined associations between executive functions and cannabis demand among young adults who use cannabis. We also examined indirect associations of executive functions with cannabis consumption and CUD symptoms through cannabis demand. Young adults (N = 113; 58.4% female; mean age 22 years) completed a Marijuana Purchase Task. Participants also completed cognitive tasks assessing executive functions (set shifting, inhibitory control, working memory) and semistructured interviews assessing past 90-day cannabis consumption (number of grams used) and number of CUD symptoms. Poorer inhibitory control was significantly associated with greater Omax (peak expenditure on cannabis) and greater intensity (cannabis consumption at zero cost). Poorer working memory was significantly associated with lower elasticity (sensitivity of consumption to escalating cost). Lower inhibitory control was indirectly associated with greater cannabis consumption and CUD symptoms through greater Omax and intensity, and poorer working memory was indirectly associated with greater cannabis consumption and CUD symptoms through reduced elasticity. This study provides novel evidence that executive functions are associated with individual differences in cannabis demand. Moreover, these results suggest that cannabis demand could be a mechanism linking poorer executive functioning with heavier cannabis use and CUD, which should be confirmed in future longitudinal studies. (PsycInfo Database Record (c) 2024 APA, all rights reserved).
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Affiliation(s)
| | - Christian S. Hendershot
- Bowles Center for Alcohol Studies, University of North Carolina–Chapel Hill, Chapel Hill, NC
- Department of Psychiatry, University of North Carolina–Chapel Hill, Chapel Hill, NC
| | - Elizabeth R. Aston
- Center for Alcohol and Addiction Studies, Department of Behavioral and Social Sciences, Brown University School of Public Health
| | - Anthony C. Ruocco
- Department of Psychological Clinical Science, University of Toronto
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Psychiatry, University of Toronto
| | - Lena C. Quilty
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Psychiatry, University of Toronto
| | - Rachel F. Tyndale
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Psychiatry, University of Toronto
- Department of Pharmacology and Toxicology, University of Toronto
| | - Jeffrey D. Wardell
- Department of Psychology, York University
- Campbell Family Mental Health Research Institute, Centre for Addiction and Mental Health, Toronto, Canada
- Department of Psychiatry, University of Toronto
- Institute for Mental Health Policy Research, Centre for Addiction and Mental Health, Toronto, Canada
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Schultz NR, Frohe T, Correia CJ, Ramirez JJ. Why get high? Coping and enjoyment motives mediate elevated cannabis demand and cannabis-related outcomes. PSYCHOLOGY OF ADDICTIVE BEHAVIORS 2023; 37:796-808. [PMID: 37326532 PMCID: PMC10524677 DOI: 10.1037/adb0000937] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
OBJECTIVE Cannabis is the most used psychoactive substance among adolescents and is a public health concern. Cannabis demand is a quantifiable measure of the reinforcing value of cannabis and comprises two latent-factors-amplitude (maximum consumption) and persistence (sensitivity to increasing costs). Cannabis demand and cannabis motives are important predictors of adolescent cannabis use and associated problems; however, little is known about how these two facets of motivation are causally related. Cannabis motives are thought to represent the final common pathway to cannabis use and may explain why elevated demand is associated with use and consequences. The present study tested whether internal cannabis motives (coping and enjoyment) mediated longitudinal associations between cannabis demand, use (hours high), and negative consequences. METHOD Participants aged 15-18 years old (n = 89, Mage = 17.0, SD = 0.9) who reported lifetime cannabis use completed online assessments of cannabis demand, motives, use and negative consequences at baseline, 3-month, and 6-month follow-up. RESULTS PROCESS mediation models revealed that enjoyment motives mediated the association between amplitude and persistence and use. In addition, coping motives mediated the association between amplitude and negative consequences. CONCLUSIONS These findings suggest that internal motives, while differentially related to aspects of demand and cannabis outcomes, are important in understanding adolescent cannabis use. Prevention efforts aimed at limiting access to cannabis and increasing access to substance-free activities may be important targets for adolescents. Further, cannabis interventions targeting specific motives for using (e.g., to cope with negative affect) may be important for reducing cannabis demand. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
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Affiliation(s)
- Nicole R. Schultz
- Department of Psychiatry & Behavioral Sciences, 2230 Stockton Blvd, University of California, Davis, Sacramento, CA 95817, USA
| | - Tessa Frohe
- Department of Psychiatry & Behavioral Sciences, Box 354944, University of Washington, Seattle, WA 98195, USA (Institution of origin)
| | - Christopher J Correia
- Department of Psychological Sciences, 226 Thach Hall, Auburn University, Auburn, AL, 36849, USA
| | - Jason J. Ramirez
- Department of Psychiatry & Behavioral Sciences, Box 354944, University of Washington, Seattle, WA 98195, USA (Institution of origin)
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González-Roz A, Martínez-Loredo V, Aston ER, Metrik J, Murphy J, Balodis I, Secades-Villa R, Belisario K, MacKillop J. Concurrent validity of the marijuana purchase task: a meta-analysis of trait-level cannabis demand and cannabis involvement. Addiction 2023; 118:620-633. [PMID: 36305652 PMCID: PMC10020890 DOI: 10.1111/add.16075] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Accepted: 10/03/2022] [Indexed: 11/29/2022]
Abstract
BACKGROUND AND AIMS The Marijuana Purchase Task (MPT) is increasingly used to measure cannabis reinforcing value and has potential use for cannabis etiological and regulatory research. This meta-analysis sought to evaluate for the first time the MPT's concurrent validity in relation to cannabis involvement. METHODS Electronic databases and pre-print repositories were searched for MPT studies that examined the cross-sectional relationship between frequency and quantity of cannabis use, problems, dependence, and five MPT indicators: intensity (i.e. unrestricted consumption), Omax (i.e. maximum consumption), Pmax (i.e. price at which demand becomes elastic), breakpoint (i.e. first price at which consumption ceases), and elasticity (i.e. sensitivity to rising costs). Random effects meta-analyses of cross-sectional effect sizes were conducted, with Q tests for examining differences by cannabis variables, meta-regression to test quantitative moderators, and publication bias assessment. Moderators included sex, number of MPT prices, variable transformations, and year of publication. Populations included community and clinical samples. RESULTS The searches yielded 14 studies (n = 4077, median % females: 44.8%: weighted average age = 29.08 [SD = 6.82]), published between 2015 and 2022. Intensity, Omax , and elasticity showed the most robust concurrent validity (|r's| = 0.147-325, ps < 0.014) with the largest significant effect sizes for quantity (|r| intensity = 0.325) and cannabis dependence (|r| Omax = 0.320, |r| intensity = 0.305, |r| elasticity = 0.303). Higher proportion of males was associated with increased estimates for elasticity-quantity and Pmax -problems. Higher number of MPT prices significantly altered magnitude of effects sizes for Pmax and problems, suggesting biased estimations if excessively low prices are considered. Methodological quality was generally good, and minimal evidence of publication bias was observed. CONCLUSIONS The marijuana purchase task presents adequate concurrent validity to measure cannabis demand, most robustly for intensity, Omax , and elasticity. Moderating effects by sex suggest potentially meaningful sex differences in the reinforcing value of cannabis.
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Affiliation(s)
- Alba González-Roz
- Peter Boris Centre for Addictions Research, St Joseph's Healthcare Hamilton, Hamilton, ON, Canada
- Addictive Behaviors Research Group, Department of Psychology, University of Oviedo, Oviedo, Spain
| | | | - Elizabeth R Aston
- Center for Alcohol and Addiction Studies, Brown University School of Public Health, Providence, RI, USA
| | - Jane Metrik
- Center for Alcohol and Addiction Studies, Brown University School of Public Health, Providence, RI, USA
- Providence VA Medical Center, Providence, RI, USA
| | - James Murphy
- Department of Psychology, The University of Memphis, Memphis, TN, USA
| | - Iris Balodis
- Peter Boris Centre for Addictions Research, St Joseph's Healthcare Hamilton, Hamilton, ON, Canada
| | - Roberto Secades-Villa
- Addictive Behaviors Research Group, Department of Psychology, University of Oviedo, Oviedo, Spain
| | - Kyla Belisario
- Peter Boris Centre for Addictions Research, St Joseph's Healthcare Hamilton, Hamilton, ON, Canada
| | - James MacKillop
- Peter Boris Centre for Addictions Research, St Joseph's Healthcare Hamilton, Hamilton, ON, Canada
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Skrzynski CJ, Napolitan A, Hitchcock L, Minhas M, Mackillop J, Bryan AD, Bidwell LC. Cannabis Involvement and Demand in Frequent Concentrate Users Versus Predominantly Flower Users. J Stud Alcohol Drugs 2023; 84:214-221. [PMID: 36971716 PMCID: PMC10171257 DOI: 10.15288/jsad.22-00066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 09/20/2022] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE Cannabis concentrate products contain more of the intoxicating cannabinoid, tetrahydrocannabinol, than flower products and, thus, may produce greater harm. Indeed, concentrate use is associated with greater cannabis dependence and problems (e.g., anxiety) than flower use. Given this, continued examination of concentrate versus flower use differences on associations with various cannabis measures may be useful. These measures include behavioral economic demand for cannabis (i.e., its subjective reinforcing value), use frequency, and dependence. METHOD In the present study of 480 cannabis users, those who were frequent concentrate users (n = 176) were compared with predominantly flower users (n = 304) regarding the relationship of two latent drug demand metrics assessed by the Marijuana Purchase Task to cannabis use frequency (i.e., days of cannabis use) and cannabis dependence (i.e., Marijuana Dependence Scale scores). RESULTS Two previously observed latent factors emerged, based on confirmatory factor analysis: amplitude, reflecting maximum consumption, and persistence, reflecting cost insensitivity. Group comparisons showed that amplitude was greater among the concentrate versus flower group, but no difference was found for persistence. Further, using structural path invariance testing, the factors were differentially associated with cannabis use frequency across groups. Amplitude was positively associated with frequency for both groups, whereas persistence was negatively associated with frequency for the flower group. Neither factor was associated with dependence for either group. CONCLUSIONS Findings continue to indicate that the demand metrics, although distinct, can be parsimoniously condensed into two factors. In addition, method of administration (i.e., concentrate vs. flower use) may affect how demand for cannabis relates to frequency of use. Associations were notably stronger with frequency relative to dependence.
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Affiliation(s)
- Carillon J. Skrzynski
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado
| | - Alexander Napolitan
- Institute of Cognitive Science, University of Colorado Boulder, Boulder, Colorado
| | - Leah Hitchcock
- Institute of Cognitive Science, University of Colorado Boulder, Boulder, Colorado
| | - Meenu Minhas
- Peter Boris Centre for Addictions Research, Department of Psychiatry and Behavioural Neurosciences, McMaster University & St. Joseph's Healthcare Hamilton, Hamilton, Ontario, Canada
| | - James Mackillop
- Peter Boris Centre for Addictions Research, Department of Psychiatry and Behavioural Neurosciences, McMaster University & St. Joseph's Healthcare Hamilton, Hamilton, Ontario, Canada
| | - Angela D. Bryan
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado
| | - L. Cinnamon Bidwell
- Department of Psychology and Neuroscience, University of Colorado Boulder, Boulder, Colorado
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Gebru NM, Jones DN, Murphy JG, Joyner KJ. A hypothetical lottery task to assess relative resource allocation toward alcohol and cannabis. PSYCHOLOGY OF ADDICTIVE BEHAVIORS 2023; 37:144-155. [PMID: 36521143 PMCID: PMC9851954 DOI: 10.1037/adb0000888] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
OBJECTIVE Relative spending on substances (vs. alternatives) is predictive of several substance use outcomes, but it can be challenging to assess. We examined a novel method of assessing relative resource allocation through the use of a hypothetical lottery task wherein participants assume they collected $100,000 United States dollars in lottery winnings and were tasked with allocating their winnings across spending categories (e.g., savings, leisure, alcohol, cannabis). We hypothesized relative allocation of funds toward alcohol and cannabis would be positively associated with more use and problems of each substance. METHOD College students (N = 479; Mage = 19.9 [SD = 2.2]) reported on their substance use and problems, alcohol and cannabis demand, and the hypothetical lottery task. RESULTS Relative resource allocation toward alcohol and cannabis on the lottery task positively correlated with alcohol and cannabis demand indices (intensity, breakpoint, Omax, and elasticity [negatively]), respectively. Using zero-inflated modeling, greater relative allocation toward alcohol positively related to alcohol use and problems in models that controlled for alcohol demand indices. For cannabis, relative resource allocation was also positively associated with cannabis use, but not problems, independently from cannabis demand indices. CONCLUSIONS Results provide initial support for the hypothetical lottery task as an indicator of relative resource allocation toward substances. Generally, these results extend previous behavioral economic research demonstrating the utility of relative resource allocation as a unique predictor of clinically relevant outcomes. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
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Affiliation(s)
- Nioud Mulugeta Gebru
- Department of Health Education and Behavior, Center for Addiction Research and Education, University of Florida
| | | | | | - Keanan J Joyner
- Department of Psychology, University of California, Berkeley
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Schultz NR, Aston ER, Metrik J, Ramirez JJ. Can I see some ID? Examining validity of the marijuana purchase task among late adolescent cannabis users. Exp Clin Psychopharmacol 2023; 31:238-247. [PMID: 35587422 PMCID: PMC9674799 DOI: 10.1037/pha0000570] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cannabis demand (i.e., reinforcing value) can be assessed using a marijuana purchase task (MPT; assesses hypothetical purchasing of cannabis at escalating prices) and has been related to use frequency, problems, and cannabis use disorder symptoms in adults. Cannabis demand has yet to be studied in adolescents, which can inform prevention and intervention efforts to reduce cannabis-related risks. The present study sought to validate the MPT with a sample of late adolescent lifetime cannabis users. Participants aged 15-18 years old (n = 115, Mage = 16.9, SD = 0.9) residing in a state with legalized cannabis use completed online assessments at baseline and 6-month follow-up. Convergent and divergent validity was examined, while principal component analysis was conducted to determine the factor structure and assess predictive validity. Three indices, Omax (i.e., maximum expenditure on cannabis), breakpoint (i.e., price suppressing consumption to zero), and alpha (i.e., degree to which consumption decreases with increasing price) were all significantly associated with cannabis use, consequences, craving, and expenditures and significantly differentiated low-risk users and high-risk users as measured by the Cannabis Use Disorders Identification Test-Revised (CUDIT-R). A two-factor solution reflecting amplitude (intensity, alpha, Omax) and persistence (breakpoint, Pmax) was observed. Both factors were associated with cannabis use and consequences in baseline regression models. At follow-up, persistence was associated with consequences; amplitude was not associated with either outcome. These findings provide initial evidence that the MPT is a valid measure for assessing cannabis demand among adolescents and can be used to understand mechanisms of adolescent cannabis use. (PsycInfo Database Record (c) 2023 APA, all rights reserved).
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Affiliation(s)
- Nicole R. Schultz
- Center for the Study of Health & Risk Behaviors (CSHRB), School of Medicine, Department of Psychiatry and Behavioral Sciences, University of Washington
| | - Elizabeth R. Aston
- Center for Alcohol and Addiction Studies, Department of Behavioral and Social Sciences, Brown University School of Public Health
| | - Jane Metrik
- Center for Alcohol and Addiction Studies, Department of Behavioral and Social Sciences, Brown University School of Public Health
- Providence VA Medical Center, Providence, Rhode Island, United States
| | - Jason J. Ramirez
- Center for the Study of Health & Risk Behaviors (CSHRB), School of Medicine, Department of Psychiatry and Behavioral Sciences, University of Washington
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Borissova A, Soni S, Aston ER, Lees R, Petrilli K, Wall MB, Bloomfield MAP, Mertzani E, Paksina A, Freeman TP, Mokrysz C, Lawn W, Curran HV. Age differences in the behavioural economics of cannabis use: Do adolescents and adults differ on demand for cannabis and discounting of future reward? Drug Alcohol Depend 2022; 238:109531. [PMID: 35809475 DOI: 10.1016/j.drugalcdep.2022.109531] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2021] [Revised: 04/28/2022] [Accepted: 04/29/2022] [Indexed: 11/03/2022]
Abstract
BACKGROUND Adolescence is a period of psychological and neural development in which harms associated with cannabis use may be heightened. We hypothesised that adolescent who use cannabis (adolescentsWUC) would have steeper delay discounting (preference for immediate over future rewards) and greater demand (relative valuation) for cannabis than adults who use cannabis (adultsWUC). METHODS This cross-sectional study, part of the 'CannTeen' project, compared adultsWUC (n = 71, 26-29 years old) and adolescentsWUC (n = 76, 16-17 years old), and gender- and age-matched adolescent (n = 63) and adult (n = 64) controls. AdolescentsWUC and adultsWUC used cannabis 1-7 days/week and were matched on cannabis use frequency (4 days/week). The Monetary Choice Questionnaire assessed delay discounting. A modified Marijuana Purchase Task (MPT) assessed cannabis demand in adolescentsWUC and adultsWUC. The MPT yielded five indices: intensity (amount of cannabis used at zero cost), Omax (total peak expenditure), Pmax (price at peak expenditure), breakpoint (cost at which cannabis demand is suppressed to zero) and elasticity (degree to which cannabis use decreases with increasing price). Analyses were adjusted for covariates of gender, socioeconomic status, other illicit drug use. RESULTS Both adolescentsWUC and adultsWUC had steeper delay discounting than controls (F, (1,254)= 9.13, p = 0.003, ηp2= 0.04), with no significant age effect or interaction. AdolescentsWUC showed higher intensity (F, (1,138)= 9.76, p = 0.002, ηp2= 0.07) and lower elasticity (F, (1,138)= 15.25, p < 0.001, ηp2= 0.10) than adultsWUC. There were no significant differences in Pmax, Omax or breakpoint. CONCLUSION Individuals who use cannabis prefer immediate rewards more than controls. AdolescentsWUC, compared to adultsWUC, may be in a high-risk category with diminished sensitivity to cannabis price increases and a greater consumption of cannabis when it is free.
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Affiliation(s)
- A Borissova
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom; Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom; NIHR University College London Hospitals Biomedical Research Centre, University College Hospital, London, United Kingdom.
| | - S Soni
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom
| | - E R Aston
- Center for Alcohol and Addiction Studies, Department of Behavioral and Social Sciences, Brown University School of Public Health, Providence, RI, USA
| | - R Lees
- Addiction and Mental Health Group (AIM), Department of Psychology, University of Bath, Bath, United Kingdom
| | - K Petrilli
- Addiction and Mental Health Group (AIM), Department of Psychology, University of Bath, Bath, United Kingdom
| | - M B Wall
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom; Invicro London, Burlington Danes Building, Hammersmith Hospital, Du Cane Road, London, United Kingdom
| | - M A P Bloomfield
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom; NIHR University College London Hospitals Biomedical Research Centre, University College Hospital, London, United Kingdom; Translational Psychiatry Research Group, Research Department of Mental Health Neuroscience, Division of Psychiatry, University College London, London, United Kingdom; Psychiatric Imaging Group, Medical Research Council London Institute of Medical Sciences, Imperial College London, Hammersmith Hospital, London, United Kingdom
| | - E Mertzani
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom
| | - A Paksina
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom
| | - T P Freeman
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom; Addiction and Mental Health Group (AIM), Department of Psychology, University of Bath, Bath, United Kingdom
| | - C Mokrysz
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom
| | - W Lawn
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom; National Addiction Centre, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom; Department of Psychology, Institute of Psychiatry, Psychology and Neuroscience, King's College London, London, United Kingdom
| | - H V Curran
- Clinical Psychopharmacology Unit, University College London, London, United Kingdom
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Abstract
Purpose of Review To explore relations between behavioral economic demand for cannabis and cannabis use disorder (CUD). Prior reviews have focused on drug demand in relation to use outcomes more generally. Complementing and enhancing prior work synthesizing research on cannabis demand, the present review endeavors to determine whether specific demand indices derived from the marijuana purchase task are most reliably related to CUD. Additionally, sociodemographic characteristics of participants in these studies were reviewed to identify whether certain populations were underrepresented in behavioral economic cannabis research. Recent Findings Behavioral economic demand is related to CUD; intensity and elasticity of cannabis demand were consistently associated with CUD diagnosis and severity. However, frequently, only select demand indices were assessed or reported, precluding the ability to confirm which indices are superior for denoting CUD risk. Further, most studies enrolled samples that were predominately young adults, Caucasian, and male. Summary As CUD becomes more prevalent in the wake of cannabis legalization, identification of robust predictors of CUD risk is paramount. Cannabis demand is consistently associated with CUD; however, individual indices of import in this relationship remain ambiguous. Subsequent research is needed to confirm index-specific markers of disordered cannabis use, and whether links between demand and CUD generalize across diverse populations.
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Affiliation(s)
- Elizabeth R. Aston
- Center for Alcohol and Addiction Studies, Brown University School of Public Health, Box GS121-5, Providence, RI 02912, USA
- Department of Behavioral and Social Sciences, Brown University School of Public Heath, Providence, RI 02912, USA
| | - Benjamin L. Berey
- Center for Alcohol and Addiction Studies, Brown University School of Public Health, Box GS121-5, Providence, RI 02912, USA
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