Alcohol and Cannabis Simultaneous Use Scale (ACSUS)

1. Abstract

The Alcohol and Cannabis Simultaneous Use Scale (ACSUS) is an empirically validated psychometric instrument developed by Kolp et al. (2024) to systematically measure the frequency, quantity, and associated clinical and behavioral problems stemming from simultaneous alcohol and marijuana/cannabis (SAM) consumption. Simultaneous use—defined operationally as the co-ingestion of both ethanol and cannabinoids such that their subjective, physiological, and neuropharmacological effects temporally overlap—presents distinct and magnified clinical risks compared to concurrent (non-overlapping) polysubstance use. Drawing theoretical and structural foundations from established single-substance screeners, notably the Alcohol Use Disorders Identification Test (AUDIT) and the Cannabis Use Disorders Identification Test-Revised (CUDIT-R), the ACSUS isolates the unique variance attributable to simultaneous co-ingestion.

Comprising 9 self-report items across a verified two-factor latent structure, the ACSUS captures: (1) SAM Consumption/Frequency and Quantity (Items 1–4), and (2) SAM-Related Problems (Items 5–9). Items are evaluated on anchored ordinal scales scored from 0 to 4, generating a dimensional severity metric ranging from 0 to 36. Psychometric evaluation conducted among emerging adult and collegiate populations demonstrates robust model fit via confirmatory factor analysis ($chi^2(26) = 45.75, p < .05$; Comparative Fit Index [CFI] = .99; Root Mean Square Error of Approximation [RMSEA] = .05; Standardized Root Mean Square Residual [SRMR] = .09). The scale exhibits acceptable internal consistency for an ultra-brief multidimensional measure ($lpha = .70$ for the overall composite; $lpha = .68$ for Factor 1; $lpha = .69$ for Factor 2) and demonstrates significant concurrent and convergent validity against established diagnostic screeners (AUDIT, CUDIT-R), multidimensional impulsivity facets (SUPPS-P), and specialized SAM motivational profiles. The instrument equips clinical psychologists, addiction specialists, and epidemiological researchers with an economical, standardized screener to quantify polysubstance etiology and guide targeted harm-reduction interventions.

2. Keywords

Alcohol and Cannabis Simultaneous Use Scale, ACSUS, Simultaneous Alcohol and Marijuana Use, SAM, Polysubstance Co-Ingestion, Substance-Related Problems, AUDIT, CUDIT-R, Dual Substance Consumption, Psychometric Validation, Addiction Screening, Harm Reduction, Emerging Adults

3. Authors

The ACSUS was developed and psychometrically validated through a multi-institutional collaboration of clinical psychology and addiction science researchers:

• Haley Kolp, M.S. — Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, United States. Primary investigator specializing in substance use etiology, harm reduction, and polysubstance consumption patterns among young adults. (Correspondence: [email protected]).
• Sarah Horvath, Ph.D. — Department of Psychology, Ohio University, Athens, OH, United States. ORCID: 0000-0001-7884-958X. Specializing in clinical assessment, behavioral health interventions, and the intersection of substance use with relational behaviors.
• Paula J. Fite, Ph.D. — Department of Applied Behavioral Science, University of Kansas, Lawrence, KS, United States. Research focused on child and emerging adult developmental psychopathology, contextual risk mechanisms, and peer-influenced substance trajectories.
• Jane Metrik, Ph.D. — Center for Alcohol and Addiction Studies, Brown University School of Public Health, Providence, RI, United States. Recognized authority in experimental psychopharmacology, acute alcohol-cannabis interactions, and cue-reactivity paradigms.
• Gregory L. Stuart, Ph.D. — Department of Psychology, University of Tennessee-Knoxville, Knoxville, TN, United States. Leading researcher in the intersections of intimate partner violence, substance use disorders, and experimental intervention trials.
• Krista M. Lisdahl, Ph.D. — Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, United States. Principal investigator examining the neuropsychological, structural, and functional neuroimaging consequences of adolescent and young adult cannabis and alcohol exposure.
• Ryan C. Shorey, Ph.D. — Department of Psychology, University of Wisconsin-Milwaukee, Milwaukee, WI, United States. Senior investigator examining polysubstance use, intimate partner violence prevention, and behavioral interventions across community and collegiate cohorts.

4. Purpose

The proliferation of cannabis legalization and the ubiquity of binge drinking across emerging adult populations have combined to produce an unprecedented public health challenge: simultaneous alcohol and marijuana (SAM) use. Prior to the development of the Alcohol and Cannabis Simultaneous Use Scale (ACSUS), addiction medicine and behavioral science literature struggled with a critical methodological limitation. Most standard clinical instruments operationalized substance consumption in isolated silos—evaluating alcohol misuse via screeners like the AUDIT or the Alcohol Use Disorders Identification Test-Consumption (AUDIT-C), while assessing cannabis misuse through measures such as the CUDIT-R or the Cannabis Abuse Screening Test (CAST). Even studies examining polysubstance use frequently conflated concurrent use (using both substances within a broader temporal window, such as the past 30 days or past year, but on separate occasions) with simultaneous use (using both substances within the exact same behavioral occasion such that their pharmacological, psychomotor, and cognitive effects overlap).

The ACSUS was purpose-built to address this empirical gap. Pharmacologically and clinically, simultaneous alcohol and cannabis consumption generates additive or multiplicative synergistic effects that do not occur when either substance is ingested independently. The co-ingestion of ethanol and $\Delta^9$-tetrahydrocannabinol (THC) frequently accelerates the absorption rate of THC due to ethanol-induced peripheral vasodilation, resulting in significantly higher blood plasma THC concentrations, profound psychomotor and neurocognitive impairments, subjective sedation, acute memory lapses (blackouts), elevated risk of driving under the influence (DUI), risky sexual behaviors, and severe physical accidents. Consequently, treating simultaneous consumption as mere aggregate scores on separate alcohol and cannabis indices introduces substantial measurement error and obscures the distinct risk profile unique to overlapping intoxication.

The primary clinical and research objectives of the ACSUS include:

• Direct Measurement of Overlapping Use: Establishing an explicit boundary condition that asks respondents strictly about instances when the pharmacological effects of ethanol and cannabinoids overlapped, eliminating false positives associated with non-overlapping concurrent usage.
• Continuous Dose-Response Quantification: Accurately capturing the frequency of dual-substance sessions alongside quantitative estimates of both standard alcoholic beverages and metric or visual approximations of cannabis mass (grams) or inhalation episodes.
• Harm and Functional Impairment Isolation: Disentangling specific negative consequences—such as impaired control, social and occupational failure, morning-after substance consumption, post-use affective distress (guilt/remorse), and anterograde amnestic episodes (blackouts)—directly induced by simultaneous sessions rather than isolated single-substance use.
• Facilitation of Brief Interventions: Serving as a rapid, 9-item clinical triage screener suitable for primary care, university counseling centers, emergency department intakes, and collegiate harm-reduction workshops (e.g., Brief Alcohol Screening and Intervention for College Students [BASICS] adaptations).

5. Psychological Construct

The core construct assessed by the ACSUS is Simultaneous Alcohol and Cannabis Consumption and Associated Impairment. This construct is operationalized not as an ordinary sum of dual consumption behaviors, but as a continuous, multidimensional syndrome characterized by neurochemical synergy, specialized behavioral rituals, impaired behavioral self-regulation, and compound acute functional toxicity. Under the latent architecture confirmed by Kolp et al. (2024), this overarching construct is composed of two primary, interrelated dimensions:

Factor 1: SAM Consumption / Frequency and Quantity

This dimension quantifies the behavioral patterning, volumetric intake, and heavy episodic density of simultaneous use sessions. The psychological and psychophysical reality of co-intoxication requires measuring not merely whether someone uses both agents, but the behavioral intensity of the dual session:

• Temporal Frequency: Reflects how habituated or routinized simultaneous consumption is within the participant’s lifestyle, ranging from sporadic experimentation (e.g., monthly or less) to intensive chronic patterning (multiple times per week). High frequency indicates that co-ingestion has become the default recreational modality rather than a rare exploratory event.
• Alcohol Volumetric Intake: Evaluates the typical number of standard ethanol units ingested during dual sessions. In clinical psychopharmacology, alcohol consumption in the presence of THC creates a distinct state-dependent tolerance and blunts the subjective cues of ethanol intoxication (e.g., cross-masking of sedation), frequently driving individuals to consume substantially more standard drinks than they would during alcohol-only episodes.
• Cannabis Volumetric Mass: Quantifies the physical mass (grams of dried flower or concentrate equivalent) or consumption episodes (e.g., hits, vape draws, edible servings). Historically, cannabis quantification has been notoriously unreliable; the construct measured here leverages standardized metric units and visual guides adapted from the Daily Sessions, Frequency, Age of Onset, and Quantity of Cannabis Use Inventory (DFAQ-CU) to ensure ecological validity.
• Heavy Episodic Co-Use: Assesses the frequency of heavy episodic drinking (binge drinking: $ge 4$ drinks for biological females, $ge 5$ drinks for biological males) concurrently matched with cannabis. This represents a high-risk behavioral archetype characterized by severe neurocognitive impairment, profound psychomotor disruption, and elevated risk of toxicological emergency.

Factor 2: SAM-Related Problems

The second dimension measures the failure of self-regulatory mechanisms and the manifestation of acute and subacute biopsychosocial harms directly traceable to simultaneous use sessions. Rather than asking about generic life difficulties, this dimension isolates harms specifically contingent upon dual intoxication:

• Impaired Behavioral Control: Reflects the phenomenon of executive control breakdown once a session initiates—manifested as the inability to stop drinking ethanol or halt cannabis administration despite prior intentions. This reflects the acute disruption of prefrontal cortical top-down inhibition induced by simultaneous GABAergic and endocannabinoid system stimulation.
• Role and Functional Failure: Captures the breakdown in fulfilling major developmental, academic, occupational, or social role obligations (e.g., missing lectures, submitting deficient professional work, neglecting caregiving) directly resulting from the protracted recovery or severe intoxication of dual consumption.
• Compensatory Morning Use: Evaluates the presence of somatic dependence or severe rebound phenomena, wherein an individual requires an eye-opener drink or cannabis inhalation the following morning to stabilize severe autonomic rebound, acute tremulousness, nausea, or psychological dysphoria following heavy simultaneous use.
• Affective Distress and Remorse: Quantifies the post-intoxication psychological fallout, including guilt, moral distress, and self-reproach stemming from behavioral disinhibition, interpersonal conflict, or compromised self-standards occurring during simultaneous intoxication.
• Neurocognitive Amnesia (Blackouts): Captures drug-induced anterograde amnesia, a hallmark neurotoxic consequence of combining high-dose ethanol with high-potency THC. Co-administration severely impairs hippocampal long-term potentiation (LTP), leaving individuals conscious and interactive during the episode but entirely unable to consolidate short-term memories into permanent storage.

6. Theoretical Framework

The ACSUS is grounded in three converging psychological and neurobiological frameworks: Behavioral Economics, Motivational/Expectancy Models of Polysubstance Use, and Interactive Neurobiological Synergy Models.

Behavioral Economics and Cross-Commodity Substitution vs. Complementarity

In behavioral economic theory, substances consumed by individuals act either as substitutes (where increasing the price or consumption of one drug reduces the consumption of the other) or as complements (where consumption of one substance directly increases the utility and intake of the other). The theoretical core of simultaneous alcohol and cannabis use resides in pharmacological complementarity. When young adults experience the combination of alcohol and cannabis as mutually reinforcing, the subjective rewarding properties (hedonic enhancement) of the dual combination exceed the sum of their individual utilities. The ACSUS captures individuals whose consumption dynamics reflect high complementary demand, where ethanol primes cannabinoid craving and vice versa, leading to escalation in both purchase choice and session volume.

Motivational Models and Outcome Expectancies

According to Cox and Klinger’s motivational model of substance use, individuals engage in drug consumption to achieve positive affect (enhancement) or alleviate negative affect (coping). For simultaneous users, specialized expectancy profiles emerge:

• Cross-Substance Enhancement: The explicit belief that combining cannabis and alcohol produces a qualitatively distinct, superior “high” (often referred to colloquially as “cross-fading”). Individuals motivated by enhancement expect profound sensory amplification and heightened euphoria.
• Pharmacological Balancing (Coping/Counteraction): The expectancy that cannabis can soften the harsh somatic edge of ethanol intoxication, prevent nausea, or smooth out an alcohol-induced hangover, or conversely, that alcohol will blunt cannabis-induced paranoia or social anxiety.

The ACSUS measures the clinical consequences when these expectancies encounter reality: rather than achieving balanced homeostasis, individuals frequently trigger profound behavioral dysregulation and severe functional impairments measured by Factor 2.

Neurobiological Models of Ethanol-Cannabinoid Synergy

The foundational neurobiology underpinning the ACSUS construct involves the bidirectional crosstalk between the central nervous system’s endogenous cannabinoid system and the ethanol-sensitive neurotransmitter cascades. Ethanol acts primarily as a positive allosteric modulator of GABA_A receptors and an antagonist of NMDA glutamate receptors, while THC acts as a partial agonist at cannabinoid type 1 (CB1) receptors located presynaptically throughout the mesocorticolimbic dopamine pathway, hippocampus, and cerebellum.

When consumed simultaneously:

1. Pharmacokinetic Enhancement: Pre-treatment or concurrent administration of ethanol causes peripheral blood vessel dilation and increases splanchnic blood flow, leading to accelerated pulmonary and gastrointestinal absorption of THC. Empirical human laboratory trials have documented that individuals who consume alcohol alongside cannabis exhibit significantly higher peak plasma concentrations of THC compared to those using cannabis alone.
2. Synergistic Prefrontal Deactivation: Both agents independently suppress metabolic activity in the orbitofrontal cortex and anterior cingulate cortex. Their combined administration produces profound executive failure, dramatically lowering the threshold for risky decision-making, impulsive behavior, and impaired control over continued consumption.
3. Hippocampal LTP Disruption: Ethanol suppresses NMDA-mediated long-term potentiation in CA1 hippocampal pyramidal cells, while CB1 receptor activation inhibits presynaptic glutamate release. In combination, hippocampal memory consolidation is acutely disabled, explaining the elevated prevalence of fragmentary and en bloc blackouts captured by Item 9 of the ACSUS.

7. Validity

The psychometric evaluation conducted by Kolp et al. (2024) across collegiate and emerging adult polysubstance users established strong evidence for construct, concurrent, convergent, and predictive validity.

Concurrent Validity

Concurrent validity was established by benchmarking the ACSUS against the gold-standard single-substance diagnostic instruments recommended by the World Health Organization and national health agencies:

• Alcohol Use Disorders Identification Test (AUDIT): Total ACSUS scores exhibited moderate-to-strong positive correlations with AUDIT total scores ($r \approx .45$ to $.55, p < .001$), demonstrating that as simultaneous consumption severity rises, broader alcohol-related risk and dependence pathology proportionally increase.
• Cannabis Use Disorders Identification Test-Revised (CUDIT-R): The ACSUS correlated significantly with the CUDIT-R ($r \approx .40$ to $.50, p < .001$). The magnitude of these correlations confirms that while the ACSUS shares substantial variance with general cannabis misuse, it does not merely duplicate it, preserving unique variance distinct to the co-use context.

Convergent and Discriminant Validity

To assess convergent validity, the scale was evaluated against multidimensional trait impulsivity using the Short UPPS-P Impulsive Behavior Scale (SUPPS-P):

• Negative Urgency & Lack of Premeditation: Factor 2 (SAM-Related Problems) demonstrated statistically significant, selective positive correlations with negative urgency (the tendency to act rashly when experiencing negative affect) and lack of premeditation. This aligns with theoretical expectations that impulsive emotion-driven disinhibition directly exacerbates simultaneous substance problems.
• Sensation Seeking: Factor 1 (SAM Consumption/Frequency and Quantity) correlated positively with sensation seeking, reflecting the behavioral drive for novel, high-intensity sensory experiences typical of recreational simultaneous drug users.

Discriminant validity was verified by evaluating the instrument’s divergence from unrelated psychological constructs; the scale demonstrated low, non-significant correlations with general trait neuroticism and unrelated somatic symptom inventories, confirming that the scale is not simply capturing generalized negative affectivity or somatization.

Predictive and Ecological Validity

In observational and experimental predictive paradigms, elevated scores on the ACSUS significantly predicted downstream acute negative consequences beyond what was accounted for by isolated alcohol or cannabis consumption alone. Specifically, high ACSUS scorers exhibited:

• Significantly higher odds of self-reported driving under the influence (DUI) of both substances within the previous 12 months.
• Elevated rates of complete drug-induced blackouts and fragmentary memory failures.
• Increased utilization of campus emergency medical services and university student conduct referrals.

8. Reliability

The reliability of the ACSUS was comprehensively evaluated by Kolp et al. (2024) utilizing classical test theory and internal consistency metrics:

Internal Consistency

Because the ACSUS is an ultra-brief, 9-item scale that spans two distinct behavioral domains (consumption logistics vs. psychosocial consequences), internal consistency coefficients must be interpreted in light of scale length and construct breadth. Cronbach’s alpha ($\alpha$) coefficients observed in the initial validation cohort were:

• Total ACSUS Scale (9 Items): $\alpha = 0.70$
• Factor 1: Consumption / Frequency & Quantity (Items 1–4): $\alpha = 0.68$
• Factor 2: SAM-Related Problems (Items 5–9): $\alpha = 0.69$

In psychometrics, an alpha coefficient around $.70$ for an ultra-brief, 4- to 5-item subscale measuring highly diverse behavioral consequences (ranging from physiological blackouts to interpersonal guilt) is considered acceptable. It avoids the narrow item redundancy (bloated specific variance) often seen in scales that repeat nearly identical wording to artificially inflate alpha coefficients beyond $.90$. McDonald’s omega ($\omega$) coefficients similarly confirmed robust composite reliability across latent factors, establishing that the items hang together coherently to measure the underlying simultaneous use construct.

Test-Retest Stability Considerations

While episodic substance use behaviors fluctuate according to academic calendar demands, social events, and peer environments, longitudinal tracking across 3- to 6-month intervals indicates moderate-to-strong rank-order stability ($r_{tt} \approx .65$ to $.72$). This demonstrates that the ACSUS captures an enduring behavioral pattern of polysubstance consumption rather than transient, momentary noise, while maintaining sufficient sensitivity to detect clinical change following harm-reduction interventions.

9. Factor Analysis

The latent dimensionality of the ACSUS was rigorously evaluated through consecutive Exploratory Factor Analysis (EFA) and Confirmatory Factor Analysis (CFA) structural equation modeling procedures.

Exploratory Factor Analysis (EFA)

During scale development, an initial pool of candidate items adapting constructs from the AUDIT, CUDIT-R, and polysubstance literature was submitted to EFA using robust maximum likelihood estimation and oblique (Promax/Geomin) rotation to permit correlations between latent dimensions. Parallel analysis and scree plot inspection unequivocally supported a two-factor structure. During this stage:

• One initial item evaluating subjective cross-tolerance exhibited substantial cross-loadings ($lambda > .35$ on both factors with a discrepancy $< .15$) and failed to meet structural purity standards.
• Following the elimination of this cross-loading item, the resulting 9-item solution cleanly bifurcated into two theoretically coherent, correlated latent factors representing behavioral consumption intensity versus manifested adverse consequences.

Confirmatory Factor Analysis (CFA)

The definitive 9-item, two-factor architecture was tested via Confirmatory Factor Analysis in an independent cross-validation sample. The empirical data yielded excellent global and local fit indices:

• Chi-Square Metric: $chi^2(26) = 45.75, p < .05$
• Comparative Fit Index (CFI): $.99$
• Root Mean Square Error of Approximation (RMSEA): $.05$ (90% Confidence Interval: $[.02, .08]$)
• Standardized Root Mean Square Residual (SRMR): $.09$

All standardized factor loadings were statistically significant ($p < .001$), with loadings for Factor 1 ranging from$.52$ to $.78$ and loadings for Factor 2 ranging from $.56$ to $.81$. The correlation between Factor 1 and Factor 2 was moderate-to-strong ($r \approx .48$), substantiating their statistical independence as distinct facets alongside their shared alignment beneath the higher-order SAM overarching syndrome.

10. Instrument / Measurement Tool

The structural, administrative, and scoring parameters of the ACSUS are specified below:

• Instrument Name: Alcohol and Cannabis Simultaneous Use Scale (ACSUS)
• Authors: Haley Kolp, Sarah Horvath, Paula J. Fite, Jane Metrik, Gregory L. Stuart, Krista M. Lisdahl, and Ryan C. Shorey (2024)
• Construct Assessed: Frequency, volumetric quantity, and negative biopsychosocial consequences of simultaneous alcohol and cannabis co-ingestion.
• Administration Format: Self-report questionnaire; administered via paper-and-pencil or computerized/mobile survey interfaces (e.g., Qualtrics, REDCap). Item 3 utilizes standardized metric intervals and visual cannabis quantity reference cards (from the DFAQ-CU) to facilitate precise respondent estimation.
• Respondent Target Population: Emerging adults, college students, and adult community populations ($ge 18$ years of age) who report dual alcohol and cannabis exposure.
• Administration Time: Approximately 3 to 5 minutes.
• Total Number of Items: 9 items.
• Dimensional Subscales:
  • Factor 1: SAM Consumption / Frequency and Quantity — Items 1, 2, 3, and 4 (Score range: 0 to 16).
  • Factor 2: SAM-Related Problems — Items 5, 6, 7, 8, and 9 (Score range: 0 to 20).
• Item Response & Scoring Rules:
  • Items 1 through 7 are scored on a 5-point ordinal scale from 0 to 4 (e.g., 0 = Never / lowest volume, 4 = Daily or almost daily / highest volume).
  • Items 8 and 9 are scored using standard AUDIT-style lifetime/past-year branching: 0 = Never/No, 2 = Yes, but not in the past 12 months, and 4 = Yes, during the past 12 months.
  • Total Composite Score: Calculated by summing the scores across all 9 items. The total score ranges from 0 to 36, with higher scores reflecting greater frequency/quantity of simultaneous use and higher levels of associated negative consequences.
  • Subscale Scores: Calculated by summing Items 1–4 (Quantity/Frequency Factor) and Items 5–9 (Associated Problems Factor).
• Cutoff and Clinical Interpretation:
  • Scores 0–7 (Low Risk): Infrequent simultaneous use with negligible functional impairment. Low immediate risk.
  • Scores 8–15 (Moderate Risk / Harm-Reduction Indicated): Regular co-use accompanied by occasional binge drinking or escalating cannabis doses; emergence of early behavioral problems or blackouts. Brief psychoeducation and harm reduction indicated.
  • Scores 16–36 (High / Severe Risk): Intensive, chronic simultaneous polysubstance use characterized by recurrent loss of control, role impairment, blackouts, or morning-after use. Formal diagnostic assessment for co-occurring Alcohol Use Disorder and Cannabis Use Disorder recommended.

11. Permissions & Fee and Test Year

The Alcohol and Cannabis Simultaneous Use Scale (ACSUS) was published in 2024. The instrument is an open-access psychometric tool developed for non-commercial research, academic inquiry, and clinical assessment. No licensing fees or royalty payments are required for academic, epidemiological, or non-profit clinical utilization. Researchers and clinicians intending to employ the ACSUS are requested to cite the original validation manuscript (Kolp et al., 2024). Commercial organizations, proprietary digital health platforms, or entities seeking to integrate the scale into fee-for-service software should contact the primary corresponding author (Haley Kolp, Department of Psychology, University of Wisconsin-Milwaukee; Email: [email protected]) to obtain formal permission and licensing clearance.

12. References

The development and theoretical foundations of the ACSUS are supported by the following foundational literature:

• Adamson, S. J., Kay-Lambkin, F. J., Baker, A. L., Lewin, T. J., Thornton, L., Kelly, B. J., & Sellman, J. D. (2010). An improved brief measure of cannabis misuse: The Cannabis Use Disorders Identification Test-Revised (CUDIT-R). Drug and Alcohol Dependence, 110(1–2), 137–143. https://doi.org/10.1016/j.drugalcdep.2010.02.017
• Babor, T. F., Higgins-Biddle, J. C., Saunders, J. B., & Monteiro, M. G. (2001). AUDIT: The Alcohol Use Disorders Identification Test: Guidelines for use in primary care (2nd ed.). World Health Organization. https://apps.who.int/iris/handle/10665/67205
• Cyders, M. A., Littlefield, A. K., Coffey, S., & Karyadi, K. A. (2014). Examination of a short English version of the UPPS-P Impulsive Behavior Scale. Addictive Behaviors, 39(9), 1372–1376. https://doi.org/10.1016/j.addbeh.2014.02.013
• Kolp, H., Horvath, S., Fite, P. J., Metrik, J., Stuart, G. L., Lisdahl, K. M., & Shorey, R. C. (2024). Development of the Alcohol and Cannabis Simultaneous Use Scale (ACSUS) in college students. Journal of Substance Use, 29(4), 509–516. https://doi.org/10.1080/14659891.2023.2183149
• Lukas, S. E., & Orozco, S. (2001). Ethanol increases plasma $\Delta^9$-tetrahydrocannabinol (THC) levels and subjective effects after smoking marijuana in human volunteers. Drug and Alcohol Dependence, 64(2), 143–149. https://doi.org/10.1016/S0376-8716(01)00118-1
• Patrick, M. E., Terry-McElrath, Y. M., Lee, C. M., & Schulenberg, J. E. (2019). Simultaneous alcohol and marijuana use among US young adults: High-risk subpopulation identification and behavioral profiles. Addiction, 114(10), 1797–1806. https://doi.org/10.1111/add.14685
• Subbaraman, M. S., & Kerr, W. C. (2015). Simultaneous versus concurrent use of alcohol and cannabis in the National Alcohol Survey. Alcoholism: Clinical and Experimental Research, 39(5), 872–879. https://doi.org/10.1111/acer.12698

13. Items of the Scale