Using recursive partitioning to predict presence and severity of suicidal ideation amongst college students.

OBJECTIVE: Predicting the presence and severity of suicidal ideation in college students is important, as deaths by suicide amongst young adults have increased in the past 20 years. PARTICIPANTS: We recruited college students (N = 5494) from ten universities across eight states. METHOD: Participants answered three questionnaires related to lifetime and past month suicidal ideation, and an indicator of suicidal ideation in a DSM-5 symptom measure. We used recursive partitioning to predict the presence, absence, and severity, of suicidal ideation. RESULTS: Recursive partitioning models varied in their accuracy and performance. The best-performing model consisted of predictors and outcomes measured by the DSM-5 Level 1 Cross-Cutting Symptom Measure. Sexual orientation was also an important predictor in most models. CONCLUSIONS: A single measure of DSM-5 symptom severity may help universities understand suicide severity to promote targeted interventions. Though further work is needed, as similar scaling amongst predictors could have influenced the model.

Regression tree applications to studying alcohol-related problems among college students.

Machine learning algorithms hold promise for developing precision medicine approaches to addiction treatment yet have been used sparingly to identify predictors of alcohol-related problems. Recursive partitioning, a machine learning algorithm, can identify salient predictors and clinical cut points that can guide treatment. This study aimed to identify predictors and cut points of alcohol-related problems and to examine result stability in two separate, large data sets of college student drinkers (n = 5,090 and 2,808). Four regression trees were grown using the "rpart" package in R. Seventy-one predictors were classified as demographics (e.g., age), alcohol use indicators (e.g., typical quantity/frequency), or psychosocial indicators (e.g., anxiety). Predictors and cut points were extracted and used to manually recreate the tree in the other data set to test result stability. Outcome variables were alcohol-related problems as measured by the Alcohol Use Disorder Identification Test and Brief Young Adult Alcohol Consequences Questionnaire. Coping with depression, conformity motives, binge drinking frequency, typical/heaviest quantity, drunk frequency, serious harm reduction protective behavioral strategies, substance use, and psychosis symptoms best predicted alcohol-related problems across the four trees; coping with depression (cut point range: 1.83-2.17) and binge drinking frequency (cut point range: 1.5-2.5) were the most common splitting variables. Model fit indices suggest relatively stable results accounting for 17%-30% of the variance. Results suggest the nine salient predictors, particularly coping with depression motives scores around 2 and binge drinking frequency around two to three times per month, are important targets to consider when treating alcohol-related problems for college students. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Study Protocol for the Healing Opioid Misuse and Pain Through Engagement Trial: Integrated Treatment for Individuals With Co-occurring Chronic Pain and Opioid Use Disorder.

Chronic pain and opioid use disorder (OUD) are public health crises and their co-occurrence has led to further complications and public health impacts. Provision of treatments for comorbid chronic pain and OUD is paramount to address these public health crises. Medications for OUD (MOUD) are gold standard treatments for OUD that have also demonstrated benefit in pain management. However, clinics that provide MOUD for chronic pain or OUD often lack behavioral treatments to address the challenges experienced by individuals with both conditions. Developing and implementing a behavioral treatment that complements MOUD may better equip clinics to provide comprehensive care to the growing proportion of clients who present with comorbid chronic pain and OUD. In the Healing Opioid misuse and Pain through Engagement (HOPE) Trial, we are using an effectiveness-implementation hybrid design to examine the benefits of an integrated behavioral treatment and to determine the feasibility of implementing the integrated treatment into clinics that provide MOUD. The treatment integrated 2 evidence-based treatments-Acceptance and Commitment Therapy and Mindfulness-Based Relapse Prevention-to target the emotional, behavioral, and physiological sequelae of OUD and chronic pain. Implementation feasibility will include assessing changes in implementation readiness and identifying facilitators and barriers to implementing the integrated treatment among all personnel employed in clinics that provide MOUD. This commentary offers an overview of the study and design and details adaptations we made to our study protocol, based largely on clinic personnel time constraints and variable clinic procedures during the COVID-19 pandemic.

Development and validation of the Substance Use Protective Strategies Scale (SUPSS) among Polish young adults using various psychoactive substances.

Research supports protective behavioral strategies (PBS) as effective in reducing substance use, intoxication, and/or related risks/harms. However, despite the predominance of polysubstance use and common co-occurrence of different substance use disorders (SUDs), previous PBS research has been limited in terms of substance-specific measurement. This study sought to develop and validate a measure of PBS that is not substance-specific. Building from initial pilot work, we tested the psychometric properties of the Substance Use Protective Strategies Scale (SUPSS) in a large sample of young adults (N = 7325, aged 18-30), who reported using multiple psychoactive substances (other than alcohol and nicotine), recruited via social media in Poland. By splitting the sample, we conducted exploratory (n = 3709) and confirmatory factor analysis (n = 3614), which supported a 4-factor structure with 19 items (7 items dropped): Preparation for use (α = 0.66), Manner of use (α = 0.85), Additional concerns (α = 0.74), and Setting (α = 0.62). Configural, metric and scalar invariance were supported across sex, age, and user status for most substance types (cannabis, dissociatives, etc.). Further, the SUPSS factors were strongly associated with substance-related harms (R-squared = 0.495) and SUD symptoms (DUDIT, R-squared = 0.570). Our model fit was adequate (but not excellent), and two subscales had low internal consistency, highlighting the need for further improvement of the SUPSS. Despite its limitations, we found the SUPSS to have strong psychometric properties and it holds promise to enhance PBS research and harm reduction-oriented interventions.

Resilience Through Harm Reduction? Protective Behavioral Strategies as a Factor of Resilience Among Polish Young Adults Using Various Psychoactive Substances.

Resiliency theory might provide a conceptual framework for understanding why adverse substance-related consequences vary considerably among young adults using psychoactive substances. Protective behavioral strategies (PBS) are behaviors that reduce substance use and related consequences. Despite such suggestions, to date no research has explicitly treated PBS as resilience factors. The purpose of this study was to examine compensatory and protective models of resilience among young adults using various substances. Data were obtained from an online questionnaire distributed through online social networks. Participants were Polish young adults (18-30 years old; M = 22, SD = 3.6; about 30% female and 1.3% non-binary; N = 7253), who reported using substances, other than alcohol or nicotine, in the last 12 months. After controlling for sociodemographics, hierarchical regression analyses of both substance-related harms and SUDs indicated the main effects of risk and protective factors, and the interaction between substance use and PBS. The models explained about 50% and 52% of the dependent variables variance, respectively. The results of this cross-sectional study provide support for both compensatory and protective models of resilience. This presents a rationale for recognizing PBS use as resilience factors that help young adults reduce substance-related harms. Theoretical discussion and practical implications are provided.

Profiles of alcohol and cannabis protective behavioral strategies use across two large, multi-site college student samples of concurrent alcohol and cannabis users.

Concurrent use of alcohol and cannabis among college students is common and confers greater harms than the use of either of these substances alone. Large and growing bodies of literature have demonstrated the independent utility of behaviors used before, during, after, or instead of alcohol and cannabis use that minimize related harms (i.e., protective behavioral strategies [PBS]). However, little is known about the relationship between alcohol and cannabis PBS and their joint influence on harms among college students who concurrently use alcohol and cannabis. In the present study, we used data from two large, multi-site samples of college students, and restricted analyses to those who reported at least one episode of alcohol and cannabis use in the past 30 days (Study 1: N = 1104[Mage = 20.3, SD = 3.8; 70.0 % female; 79.5 % white]; Study 2: N = 2034[Mage = 20.2, SD = 3.2; 69.1 % female; 76.6 % white]). A latent profile analysis supported a 4-profile solution that was largely consistent across samples: Profile 1 (low alcohol/cannabis PBS; 8.8-11.9 %), Profile 2 (average alcohol/cannabis PBS; 33.1-37.7 %), Profile 3 (average alcohol PBS/low cannabis PBS; 16.3-25.2 %), and Profile 4 (high alcohol/cannabis PBS; 29.8-37.2 %). Profile 4 reported the least alcohol/cannabis use, fewest negative alcohol-/cannabis-related consequences, and lowest alcohol/cannabis use severity. In contrast, Profile 1 was the opposite for alcohol-related outcomes, and Profile 3 was the opposite for cannabis-related outcomes. These findings are preliminary but may suggest that targeting both alcohol and cannabis PBS in intervention is generally beneficial except some groups at risk for a particular substance may benefit from increased focus on that substance in intervention.

Utility of the Brief Young Adult Alcohol Consequences Questionnaire to Identify College Students At-Risk for Alcohol Related Problems: Relative Operating Characteristics across Seven Countries.

Background: It is important to identify students who would benefit from early interventions to reduce harmful drinking patterns and associated consequences. the Brief Young Adult Alcohol Consequences Questionnaire (B-YAACQ) could be particularly useful as a screening tool in university settings. Objectives. The present study examined the utility of the B-YAACQ to distinguish among students at-risk for problematic alcohol use as measured by the AUDIT. Objectives: The present study examined the utility of the B-YAACQ to distinguish among students at-risk for problematic alcohol use as measured by the AUDIT. Methods: A sample of 6382 students (mean age=20.28, SD=3.75, 72.2% females) from seven countries (i.e., U.S., Canada, South-Africa, Spain, Argentina, Uruguay, England) completed the B-YAACQ, the AUDIT and different measures of alcohol use. Results: ROC analyses suggested that a cutoff score of 5 maximized the YAACQ's discrimination utility to differentiate between students at low versus moderate/high risk in the total sample and across countries (except in Canada, where the cutoff was 4). In addition, a cutoff of 7 differentiated between students at low/moderate versus high risk in the total sample, while cutoffs of 10, 9, 8 and 7 differentiate between students at low/moderate versus high risk in Uruguay, U.S and Spain (10), Argentina (9), England (8), and Canada and South-Africa (7), respectively. Students classified at the three risk levels (i.e., low, moderate and high) differed in age (i.e., a younger age was associated with higher risk) and drinking patters (i.e., higher drinking frequency, quantity, binge drinking and AUDIT and B-YAACQ scores in the higher risk groups). Conclusions: This study suggest that the B-YAACQ is a useful tool to identify college students at-risk for experiencing problematic patterns of alcohol use.

Early Birds and Night Owls: Distinguishing Profiles of Cannabis Use Habits by Use Times with Latent Class Analysis.

Background: Understanding, predicting, and reducing the harms associated with cannabis use is an important field of study. Timing (i.e., hour of day and day of week) of substance use is an established risk factor of severity of dependence. However, there has been little attention paid to morning use of cannabis and its associations with negative consequences. Objectives: The goal of the present study was to examine whether distinct classifications of cannabis use habits exist based on timing, and whether these classifications differ on cannabis use indicators, motives for using cannabis, use of protective behavioral strategies, and cannabis-related negative outcomes. Methods: Latent class analyses were conducted on four independent samples of college student cannabis users (Project MOST 1, N=2,056; Project MOST 2, N=1846; Project PSST, N=1,971; Project CABS, N=1,122). Results: Results determined that a 5-class solution best fit the data within each independent sample consisting of the classes: (1) "Daily-morning use",(2) "Daily-non-morning use", (3) "Weekend-morning use", (4) "Weekend-night use", and (5) "Weekend-evening use." Classes endorsing daily and/or morning use reported greater use, negative consequences and motives, while those endorsing weekend and/or non-morning use reported the most adaptive outcomes (i.e., reduced frequency/quantity of use, fewer consequences experienced, and fewer cannabis use disorder symptoms endorsed). Conclusions: Recreational daily use as well as morning use may be associated with greater negative consequences, and there is evidence that most college students who use cannabis do avoid these types of use. The results of the present study offer evidence that timing of cannabis use may be a pertinent factor in determining harms associated with use.

Measuring Readiness to Change Substance Use, Alcohol Use, and Cannabis Use: An Experimental Manipulation of Cognitive Effort.

Background: The Transtheoretical Model supports that readiness to change should predict actual substance-related behavior change. This relationship is surprisingly modest. Across several behavioral domains, individuals tend to have unrealistic expectations regarding the amount of effort and time required to successfully change one's behaviors, dubbed the False Hope Syndrome. Objectives: Based on False Hope Syndrome, we expect the standard method of measuring self-reported readiness to change is overestimated. To test this hypothesis, we experimentally manipulated level of cognitive effort prior to completing readiness to change measures. College students from a large southwestern university who reported using substances in the past 30 days (n = 345) were recruited from a psychology department participant pool and randomized to one of three conditions: 1) standard, low effort condition, 2) medium effort condition (selected likes/dislikes of substance use and negative consequences of changing one's use), and 3) high effort condition (also provided written responses to how they would handle difficult situations related to changing their substance use). We conducted one-way ANOVAs with Tukey post-hoc comparisons to examine differences on three measures of readiness to change: the University of Rhode Island Change Assessment (URICA) scale as well as readiness and motivation rulers. Results: Contrary to our hypothesis, all significant statistical tests supported higher cognitive effort conditions reporting higher readiness to change. Although effect sizes were modest, higher cognitive effort appeared to increase self-reported readiness to change substance use. Conclusions: Additional work is needed to test how self-reported readiness to change relates to actual behavior change when assessed under the different effort conditions.

The Associations of Basic Psychological Need Satisfaction and Need Frustration with Cannabis-Related Outcomes in a Multi-Site Sample of College Students.

Psychological need satisfaction and need frustration, proposed by self-determination theory, may serve as conditions that foster health-promoting and health-impairing behaviors related to cannabis use. In the present study, we examined the measurement model of psychological need satisfaction and need frustration and their associations with cannabis protective behavioral strategies use, negative cannabis-related consequences, and cannabis use severity. Data were from 1394 college students from 10 universities across the U.S. who reported past-month cannabis use. A higher-order factor model representing general psychological need satisfaction and need frustration provided a good fit to the data. Regressing the three observed cannabis outcome variables onto these higher-order latent factors, we found that greater need satisfaction was associated with more frequent cannabis protective behavioral strategies use and fewer negative cannabis-related consequences. Greater need frustration was associated with greater negative cannabis-related consequences and cannabis use severity. Further, an interaction effect between need satisfaction and need frustration emerged for each cannabis outcome such that greater need satisfaction attenuated the associations between need frustration and cannabis outcomes and greater need frustration strengthened the associations between need satisfaction and cannabis outcomes. Implications for the roles of need satisfaction and need frustration in cannabis use and future intervention development are discussed.

Trajectories of change in subclinical anxiety and alcohol use during alcohol treatment: A parallel process growth model.

BACKGROUND: Anxiety is implicated in the course and prognosis of alcohol use disorder (AUD); however, it is unclear how current AUD treatments affect the joint trajectories of anxiety and alcohol use. We used data from the Combined Pharmacotherapies and Behavioral Interventions for Alcohol Dependence (COMBINE) study to examine the longitudinal relationship between subclinical anxiety symptoms and alcohol use during and following AUD treatment in adults with AUD and no comorbid anxiety disorders. METHODS: Univariate and parallel process growth models using five waves of COMBINE study data were analyzed from 865 adults randomized to medication (n = 429) or medication plus psychotherapy (n = 436). Weekly drinking quantity and average weekly anxiety symptoms were measured at baseline, mid-treatment, end-of-treatment, and three follow-up periods. RESULTS: Significant positive associations of anxiety symptoms and drinking were found at mid-treatment and over time. Temporal associations revealed that higher mid-treatment anxiety predicted decreases in drinking over time. Baseline anxiety and drinking predicted mid-treatment anxiety and drinking. Only baseline anxiety predicted increases in drinking over time. Group differences revealed mid-treatment drinking predicted decreases in anxiety over time in the medication group. CONCLUSIONS: Findings demonstrate the influence of subclinical anxiety on alcohol use during and up to one year after AUD treatment. Baseline anxiety symptoms may influence drinking behavior over the course of treatment. Findings suggest that greater attention to negative affect in AUD treatment is warranted even for those individuals who do have a comorbid anxiety disorder.

Constructs derived from the addiction cycle predict alcohol use disorder treatment outcomes and recovery 3 years following treatment.

OBJECTIVE: The addiction cycle has been proposed as a framework for understanding the progression of alcohol use disorder (AUD) in terms of psychological and biological domains, including reward drinking/incentive salience, relief drinking/negative emotionality, and loss of control/executive functioning impairment. To have utility in clinical practice, self-report measures of these domains that are applicable across sociodemographic groups and associated with clinical outcomes are needed. This study sought to validate domains from self-report measures and to test whether domains are measurement invariant across sociodemographic groups and associated with treatment outcomes. METHOD: Secondary analysis of individuals with AUD (n = 3,092) who participated in two alcohol clinical trials, Project Matching Alcohol Treatment to Client Heterogeneity (MATCH) and COMBINE. Factor analytic methods were used to derive addiction cycle domains at baseline. These domains were then examined as predictors of outcomes. RESULTS: Fifteen self-report items were used as indicators of the addiction cycle domains, with sociodemographic differences in measurement by sex, age, race, education, and AUD symptoms. Relief/negative emotionality and reward/incentive salience were significantly associated with outcomes at 1 and 3 years following treatment, and executive functioning also predicted nonabstinent recovery at 3 years. CONCLUSIONS: The results support the utility of domains relevant to the addiction cycle in predicting AUD treatment outcomes and recovery among individuals who sought treatment for AUD. The addiction cycle domains were more strongly associated with outcomes than other measures clinicians might use to predict outcomes (e.g., AUD symptoms). Future research should continue to develop and refine the items and test whether the addiction cycle domains can inform treatment planning. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Fear of negative evaluation and suicidal ideation among college students: the moderating role of impulsivity-like traits.

Objective: Fear of negative evaluation (FNE) is a key trait of social anxiety and has been linked to isolation and low self-esteem. Impulsivity has been shown to amplify the risk of socially anxious individuals engaging in risky behaviors such as suicidal behaviors; yet little research has examined associations between FNE and suicidality or the relationship between FNE and impulsivity. Participants/Methods: This study tested whether FNE was associated with suicidal ideation in a sample of 1,816 college students from 10 universities. Analyses also examined whether impulsivity-like traits moderated the relationship between FNE and suicidal ideation. Results: Results showed that FNE was significantly associated with suicidal ideation and the positive association between FNE and suicidal ideation was strongest among individuals with higher negative urgency and lower perseverance. Conclusions: These findings highlight FNE as an important risk factor of suicidal ideation in college students and illuminates potential influence of impulsivity on this relationship.

A comprehensive examination of motivational profiles for alcohol-related behaviors among college students.

Recent research demonstrates unique relations of types of motivation for drinking responsibly based on self-determination theory and drinking motives with alcohol-related outcomes among college students. In the present study, we sought to extend prior research by using a person-centered approach to simultaneously consider types of motivation within and across these motivational constructs as well as their synergistic relations with alcohol-related outcomes. We used cross-sectional survey data from 2,808 college students at 10 universities in eight states across the United States who reported past-month alcohol use (Mage = 20.59, SD = 4.18; 72.9% female; 58.2% non-Hispanic White). A series of latent profile analyses were conducted using types of motivation for drinking responsibly and drinking motives as indicators. A five-profile solution was selected as optimal. Mean comparisons indicated that profiles defined by high endorsement of higher quality motivations for drinking responsibly (i.e., more self-determined) and low endorsement of drinking motives in combination were related to the most frequent protective behavioral strategies use, least alcohol use, and fewest negative alcohol-related consequences. Additionally, these profiles were higher on dispositional autonomy and psychological need satisfaction and lower on psychological need frustration. These findings provide initial insight into simultaneously considering motivational profiles for the interrelated behaviors of drinking responsibly and drinking that can be leveraged in college drinking interventions. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Magnesium(II)-ATP Complexes in 1-Ethyl-3-Methylimidazolium Acetate Solutions Characterized by 31 Mg ß-Radiation-Detected NMR Spectroscopy.

The complexation of MgII with adenosine 5'-triphosphate (ATP) is omnipresent in biochemical energy conversion, but is difficult to interrogate directly. Here we use the spin- 1/2 ß-emitter 31 Mg to study MgII -ATP complexation in 1-ethyl-3-methylimidazolium acetate (EMIM-Ac) solutions using ß-radiation-detected nuclear magnetic resonance (ß-NMR). We demonstrate that (nuclear) spin-polarized 31 Mg, following ion-implantation from an accelerator beamline into EMIM-Ac, binds to ATP within its radioactive lifetime before depolarizing. The evolution of the spectra with solute concentration indicates that the implanted 31 Mg initially bind to the solvent acetate anions, whereafter they undergo dynamic exchange and form either a mono- (31 Mg-ATP) or di-nuclear (31 MgMg-ATP) complex. The chemical shift of 31 Mg-ATP is observed up-field of 31 MgMg-ATP, in accord with quantum chemical calculations. These observations constitute a crucial advance towards using ß-NMR to probe chemistry and biochemistry in solution.

Using machine learning to examine predictors of treatment goal change among individuals seeking treatment for alcohol use disorder.

INTRODUCTION: The goals of individuals seeking treatment for alcohol use disorder (AUD) are typically quantified as abstinent or nonabstinent (e.g., moderate drinking) goals. However, treatment goals can vary over time and be influenced by life circumstances. This study aims to identify predictors of treatment goal change and direction of change from baseline to six-month follow-up among individuals seeking treatment for AUD. METHODS: This study is a secondary analysis of data from the Relapse Replication and Extension Project. The study included participants who completed assessments at baseline and six-month follow-up in the analysis (n = 441). We used decision trees to examine 111 potential predictors of treatment goal change. The study cross-validated results using random forests. The team examined changes in goal between baseline and follow-up (Decision Tree 1) and quantified them as being toward or away from a complete abstinence goal (Decision Tree 2). RESULTS: Nearly 50 % of the sample changed their treatment goal from baseline to 6 months, and 68.7 % changed from a nonabstinence goal toward a complete abstinence goal. The study identified seven unique predictors of goal change. The most common predictors of changing a treatment goal were number of recent treatment sessions prior to enrolling in the study, other substance use, negative affect, anxiety, social support, and baseline drinks per drinking day. Participants with a greater number of recent treatment sessions and who sought social support were most likely to change their goal. Additionally, individuals with more substance use tended to change away from complete abstinence goals. Cross-validation supported baseline drinks per drinking day, social support, baseline maximum blood alcohol concentration (BAC), lifetime tobacco use, baseline average BAC, lifetime cocaine use, Inventory of Drinking Situations total score, and Situational Confidence Questionnaire average score as important predictors. CONCLUSIONS: This study identified seven unique predictors of treatment goal change while in AUD treatment. Prior treatment, drinking to cope, and social support were most associated with goal changes. This information can inform providers who seek to understand factors associated with treatment goal selection and changes in goals during treatment.

Measurement invariance of the University of Rhode Island Change Assessment Scale in Project MATCH: An exploratory structural equation modeling approach.

BACKGROUND: Progression through the stages of change is a proposed mechanism underlying the effects of treatment for alcohol use disorder (AUD). However, examining stages of change as a mechanism of treatment effects requires that the measure be invariant across patient subgroups, treatment conditions, and time. In this study, we examined measurement invariance of the University of Rhode Island Change Assessment Scale (URICA) in Project MATCH using an exploratory structural equation modeling (ESEM) approach. METHODS: We conducted a secondary analysis of data from Project MATCH (N = 1726; Mage  = 40.2, SD = 10.9; 75.7% male; 80% non-Hispanic white), a multisite randomized clinical trial that tested three AUD treatments: Motivational Enhancement Therapy, Cognitive-Behavioral Therapy, or Twelve-Step Facilitation. Participants completed the 24-item URICA for assessing the stages of change in relation to drinking at baseline and post-treatment (3 months after baseline). RESULTS: A 4-factor ESEM provided a good fit to the data and a better fit to the data than a conventional 4-factor confirmatory factor analysis model. Further, the URICA demonstrated scalar invariance across each patient subgroup at baseline (sex, ethnicity, marital status, education, and parental history of AUD) and treatment condition at follow-up. However, the URICA was not longitudinally invariant as the metric model resulted in a significant decrement in model fit. CONCLUSIONS: Measurement invariance of the URICA over time was not supported. Longitudinally invariant measures of the stages of change are needed to test the proposal that progression through the stages explains treatment effects.

A ß-NMR study of the depth, temperature, and molecular-weight dependence of secondary dynamics in polystyrene: Entropy-enthalpy compensation and dynamic gradients near the free surface.

We investigated the depth, temperature, and molecular-weight (MW) dependence of the γ-relaxation in polystyrene glasses using implanted 8Li+ and ß-detected nuclear magnetic resonance. Measurements were performed on thin films with MW ranging from 1.1 to 641 kg/mol. The temperature dependence of the average 8Li spin-lattice relaxation time (T1 avg) was measured near the free surface and in the bulk. Spin-lattice relaxation is caused by phenyl ring flips, which involve transitions between local minima over free-energy barriers with enthalpic and entropic contributions. We used transition state theory to model the temperature dependence of the γ-relaxation, and hence T1 avg. There is no clear correlation of the average entropy of activation (Δ‡S̄) and enthalpy of activation (Δ‡H̄) with MW, but there is a clear correlation between Δ‡S̄ and Δ‡H̄, i.e., entropy-enthalpy compensation. This results in the average Gibbs energy of activation, Δ‡G, being approximately independent of MW. Measurements of the temperature dependence of T1 avg as a function of depth below the free surface indicate the inherent entropic barrier, i.e., the entropy of activation corresponding to Δ‡H̄ = 0, has an exponential dependence on the distance from the free surface before reaching the bulk value. This results in Δ‡G near the free surface being lower than the bulk. Combining these observations results in a model where the average fluctuation rate of the γ-relaxation has a "double-exponential" depth dependence. This model can explain the depth dependence of 1/T1 avg in polystyrene films. The characteristic length of enhanced dynamics is ∼6 nm and approximately independent of MW near room temperature.

Using Decision Trees to Identify Salient Predictors of Cannabis-Related Outcomes.

Cannabis use continues to escalate among emerging adults and college attendance may be a risk factor for use. Severe cases of cannabis use can escalate to a cannabis use disorder, which is associated with worse psychosocial functioning. Predictors of cannabis use consequences and cannabis use disorder symptom severity have been identified; however, they typically employ a narrow set of predictors and rely on linear models. Machine learning is well suited for exploratory data analyses of high-dimensional data. This study applied decision tree learning to identify predictors of cannabis user status, negative cannabis-related consequences, and cannabis use disorder symptoms. Undergraduate college students (N = 7000) were recruited from nine universities in nine states across the U.S. Among the 7 trees, 24 splits created by 15 distinct predictors were identified. Consistent with prior research, one's beliefs about cannabis were strong predictors of user status. Negative reinforcement cannabis use motives were the most consistent predictors of cannabis use disorder symptoms, and past month cannabis use was the most consistent predictor of probable cannabis use disorder. Typical frequency of cannabis use was the only predictor of negative cannabis-related consequences. Our results demonstrate that decision trees are a useful methodological tool for identifying targets for future clinical research.

A comprehensive examination of alcohol-related motivations among college students: Unique relations of drinking motives and motivations for drinking responsibly.

Drinking motives, or reasons people choose to drink, are well-established risk factors for alcohol use and related negative consequences. Recent research has shown utility in a self-determination theory (SDT) approach for describing motivation for engaging in behaviors that reduce the harms associated with alcohol use (i.e., drinking responsibly). In the present study, we examined the relationship between drinking motives and motivations for drinking responsibly as well as their unique and incremental associations with alcohol-related outcomes (protective behavioral strategies [PBS], consumption, and negative consequences) in two samples of college student drinkers: (a) a random sample (n = 507) recruited from a Hispanic-Serving Institution on the U.S. border with Mexico (Mage = 22.84, SD = 5.84; 67.3% female; 90.9% Hispanic) and (b) a convenience sample (n = 2,808) from Psychology Department research participation pools at 10 universities in 8 U.S. states (Mage = 20.59, SD = 4.18; 72.9% female; 58.2% non-Hispanic White). Autonomous motivations (experience of volition and choice) for drinking responsibly were negatively correlated with drinking motives, but these correlations were small-to-medium in magnitude suggesting nonredundancy between the constructs. Drinking motives were risk factors for alcohol-related outcomes, especially alcohol-related problems, and autonomous motivations for drinking responsibly were protective factors for alcohol-related outcomes, especially PBS. Both motivational constructs predicted alcohol-related outcomes beyond the other, but drinking motives generally accounted for more variance. These findings suggest that integrating motivation in relation to both drinking and drinking responsibly may lead to a better understanding of alcohol-related behaviors and the associated negative consequences among college students. Implications for college drinking interventions are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).