By Caroline Boyd-Rogers, M.A., University of Iowa
The landscape of substance use comorbidity has been changing rapidly, particularly with the widespread legalization of cannabis in many states across the United States (SAMHSA, 2021). Even in older adult populations, rates of cannabis use alone, and binge drinking and cannabis co-use, significantly increased from 2015 to 2019 (Kepner et al., 2023). These changes have important implications for research and clinical care with individuals who engage in substance use. Special consideration should be given to the impact of substance use on clinically relevant judgment and decision-making processes. This speaks to the need for clinical scientists to understand the current research on alcohol and cannabis use and their impact on clinically relevant decision-making when used separately and together. Implications of these findings for research and clinical care will be discussed.
Alcohol Use
Alcohol use can significantly bias decision-making processes. For instance, “alcohol myopia” refers to the phenomenon whereby alcohol consumption can lead an individual to increase their use of salient cues in their environment, and simultaneously experience decreased sensitivity to observing and detecting changes in more subtle cues in the environment (e.g., Davis et al., 2007; Giancola et al., 2010; Massa et al., 2019; Steele & Josephs, 1990). This is problematic, because certain, highly salient cues may be internal in nature (e.g., sexual arousal; anger) and can lead to later regretted interpersonal or health-related decisions (e.g., Davis et al., 2007; Giancola et al., 2010; Massa et al., 2019). Alcohol consumption has been repeatedly associated with relevant factors in decision-making, including increased aggression, sexual interest, risk-taking, and assertive sexual advances (e.g., Davis et al., 2007; Giancola et al., 2010; Massa et al., 2019). In addition, alcohol has been repeatedly demonstrated to affect memory, providing an additional barrier to the effective implementation of behavioral clinical interventions (e.g., Elliott et al., 2021; 2022).
Cannabis Use
Cannabis use can also affect cognitive processing which is central to judgment and decision-making (Gabrys & Porath, 2019). Because the legalization of cannabis use is still occurring, research in this field does not have as long a history as the alcohol use literature of laboratory-based experimental cannabis manipulations with standardized dosing procedures. Further, because of its legal history, cannabis has not been uniformly standardized, so relying on self-reported dosages can be less precise. Thus, definitive links between heavy cannabis use and decision-making impairment are still being studied (Gabrys & Porath, 2019). However, the evidence thus far has found that long-term cannabis use may lead to learning and memory decline over time, difficulty sustaining attention and concentration, and decreased inhibition (Gabrys & Porath, 2019). Further, long-term cannabis use has also been linked to inhibition of specific decision-making processes and is associated with increased risk-taking and increased impulsivity (Gabrys & Porath, 2019). Socially, those who regularly use cannabis may have heightened difficulties with processing the emotions of others and decreased sensitivity to exclusion by others (Gabrys & Porath, 2019). Critically, those with a diagnosed mental disorder are at least twice as likely to engage in regular cannabis use, highlighting the need to consider the generalizability of our clinical interventions to a cannabis use state (Gabrys, & Porath, 2019).
Co-occurring Alcohol and Cannabis Use
Problematically, rates of cannabis and alcohol co-use are on the rise (e.g., Roche et al., 2019; SAMHSA, 2021). The majority of individuals who report using both cannabis and alcohol report doing so concurrently (Subbaraman & Kerr, 2015). This is particularly concerning because research has shown that the use of alcohol may increase the absorption of THC in cannabis (Hartman et al., 2015), and those who engage in concurrent use tend to drink more compared to when only consuming alcohol (Subbaraman & Kerr, 2015). Co-use of these substances has been linked to more nicotine dependency, psychiatric impairment, and adverse social consequences than use of either substance in isolation (e.g., Venegas et al., 2022; Yurasek et al., 2017). Further, using cannabis and alcohol concurrently may significantly increase the likelihood of engaging in risky decision-making, such as deciding to drive while intoxicated and engaging in self-harming behavior (Subbaraman & Kerr, 2015).
Implications for Research and Clinical Care
Many clinical interventions need to consider the state-related processes that underlie clinically relevant judgment and decision-making, such as impairment to sensitivity and heightening of biases when under the influence of certain states. The college student population is one particularly important example. For instance, work in the field of sexual aggression on college campuses has examined important correlates and interventions under states such as arousal, anger, and alcohol intoxication, given the relevance of these states to undergraduate sexual decision-making (e.g., Davis et al., 2014). Thus, clinical interventions with populations at higher risk for substance use and co-use should be examined with participants in these states, as these contexts could potentially limit the effectiveness of these interventions.
Clinically, cannabis and alcohol co-use and its influences on cognitive processing and decision-making should be assessed in greater detail. For instance, it can be difficult to determine conclusively if presenting mental health concerns of clients engaging in substance use were present before use. For instance, side effects of long-term cannabis use can mimic many symptoms of ADHD (Crean, Crane, & Mason, 2011), but cannabis can also be used as a self-medication strategy for managing symptoms of ADHD (Stueber & Cuttler, 2021). This makes clinical recommendations more difficult, particularly with a paucity of research in this area. Didactics and supervision on the impacts of substance use and co-use on clinically relevant judgment and decision-making should be a more explicit part of clinical science training. Screening tools for expectancies, problems, and frequency for heavy episodic drinking (e.g. Alcohol Use Disorders Identification Test; Anticipated Effects of Alcohol Scale), cannabis use (e.g., Cannabis Use Disorders Identification Test; Marijuana Smoking Use Questionnaire; Anticipated Effects of Cannabis Scale; Rutgers Marijuana Problem Index) and their co-use (e.g. Simultaneous Alcohol and Marijuana Use Motives) should become more commonplace in initial clinical intakes (Bonn-Miller & Zvolensky, 2009; Morean et al., 2012; Saunders et al., 1993; Waddell et al., 2020; Waddell et al., 2022; White & Veliger, 1986). Further, while a large body of research has helpfully identified protective behavioral strategies for reducing risk related to drinking and risky sexual behavior (e.g., Pearson, 2013; Treat, Corbin, & Viken, 2021), and initial work has been conducted to establish a similar list for cannabis use (Pedersen et al., 2017), similar work should be done to identify these strategies related to alcohol and cannabis co-use, as these could be particularly helpful clinical recommendations for clients engaged in concurrent use of these substances.
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