Predictors of Substance Use Initiation by Early Adolescence

OBJECTIVE

Substance use initiation during early adolescence is associated with later development of substance use and mental health disorders. This study used various domains to predict substance use initiation, defined as trying any nonprescribed substance (e.g., alcohol, tobacco, cannabis), by age 12, using a large longitudinal data set.

METHODS

Substance-naive youths from the Adolescent Brain Cognitive Development Study (ages 9-10; N=6,829) were followed for 3 years. A total of 420 variables were examined as predictors of substance use initiation, using a penalized logistic regression with elastic net; domains spanned demographic characteristics, self and peer involvement with substance use, parenting behaviors, mental and physical health, culture and environment, hormones, neurocognitive functioning, and structural neuroimaging.

RESULTS

By age 12, 982 (14.4%) children reported substance initiation, with alcohol being the most common. Models with only self-report predictors had similar prediction performance to models adding hormones, neurocognitive factors, and neuroimaging predictors (AUCtest=0.66). Sociodemographic factors were the most robust predictors, followed by cultural and environmental factors, physical health factors, and parenting behaviors. The top predictor was a religious preference of Mormon (coefficient=-0.87), followed by a religious preference for Jewish (coefficient=0.32), and by Black youths (coefficient=-0.32).

CONCLUSIONS

Sociodemographic variables were the most robust predictors of substance use initiation. Adding resource-intensive measures, including hormones, neurocognitive assessment, and structural neuroimaging, did not improve prediction of substance use initiation. The application of these large-scale findings in clinical settings could help to streamline and tailor prevention and early intervention efforts.

Adolescent alcohol use is associated with differences in the diversity and composition of the oral microbiome

BACKGROUND

Adolescence is a sensitive stage of oral microbial development that often coincides with the initiation and escalation of alcohol use. Thus, adolescents may be particularly susceptible to alcohol-induced alterations in the oral microbiome, though minimal research has been done in this area. Understanding the connection between the oral microbiome and alcohol use during adolescence is important to understand fully the biological consequences of alcohol use to mitigate potential adverse outcomes.

METHODS

Saliva samples were collected from adolescents aged 17-19 who used alcohol heavily (n = 21, 52.4% female) and those who did not use alcohol or any other substances (n = 18, 44.4% female). We utilized 16S rRNA sequencing to examine differences in microbial diversity and composition between the groups.

RESULTS

For alpha diversity, evenness was significantly lower in the drinking group than the control group as indicated by Pielou's evenness, Shannon, and Simpson indices. There were no statistically significant findings for beta diversity. Differential abundance analyses revealed higher abundances of Rothia and Corynebacterium in the alcohol-using group using both centered-log-ratio and relative abundance normalization. These genera are known for their high capacity to convert alcohol into acetaldehyde, a toxic metabolite reported to play a role in the neurobiological effects of alcohol. An unclassified Clostridia UCG-014, Streptobacillus, Comamonas, unclassified Lachnospiraceae, and Parvimonas were also identified as significantly different between groups when using only one of the normalization techniques.

CONCLUSIONS

This is the first study designed specifically to compare the oral microbiome of adolescents who use alcohol with that of control participants. Our findings reveal distinct alcohol-related differences in microbial composition and taxon abundance, emphasizing the importance of understanding the impact on the oral microbiome of alcohol use during adolescence. Because the oral microbiome is malleable, this study provides foundational work for future prevention and intervention studies.

Multi-modal neuroimaging reveals differences in alcohol-cue reactivity but not neurometabolite concentrations in adolescents who drink alcohol

BACKGROUND

The objective of this multi-modal neuroimaging study was to identify neuroscience-informed treatment targets for adolescent alcohol use disorder (AUD) by examining potential neural alterations associated with adolescent alcohol use.

METHODS

Adolescents (ages 17-19) who heavily used (n=49) or did not use alcohol (n=22) were recruited for a multi-modal neuroimaging protocol, including proton magnetic resonance spectroscopy within the dorsal anterior cingulate cortex (dACC) and an fMRI alcohol cue-reactivity task. The alcohol cue-reactivity task was analyzed across 11 a priori regions-of-interest (ROI), including the dACC, and in an exploratory whole-brain approach. Correlations were run between neurometabolite levels and alcohol cue-reactivity in the dACC.

RESULTS

There were no significant group differences in absolute neurometabolite concentrations. Compared to the control group, the alcohol-using group exhibited heightened alcohol cue reactivity in the left amygdala ROI (p=0.04). The whole-brain approach identified higher alcohol cue reactivity in the alcohol-using group compared to controls in the amygdala and occipital regions, and lower reactivity in the parietal lobe. Whole-brain sex effects were noted, with females displaying higher reactivity regardless of group. No significant correlations were found between neurometabolite levels and alcohol cue-reactivity in the dACC.

CONCLUSIONS

The null neurometabolic findings may be due to age, relatively low severity of alcohol use, and non-treatment-seeking status of the participants. Females showed overall higher reactivity to alcohol cues, indicating a sex effect regardless of alcohol use history. Higher amygdala reactivity in alcohol-using adolescents suggests that emotional processing related to alcohol cues may be a useful target for future adolescent AUD interventions.

The adolescent and young adult microbiome and its association with substance use: a scoping review

AIMS

The microbiome is a critical factor in health throughout human development. The aims of this scoping review are to (i) elucidate the differences between the youth (post-natal day 21-65 for rodents, 2-7 years for non-human primates, and 10-25 years for humans) microbiome with other life stages and (ii) identify youth-specific microbial changes associated with substance use.

METHODS

Peer-reviewed studies published up to May 2023 were identified in PubMed and SCOPUS and included gut and oral microbiome studies from rodents, non-human primates, and humans (N = 1733). Twenty-six articles were determined eligible based on inclusion criteria (aim 1: n = 19, aim 2: n = 7).

RESULTS

The adolescent and young adult oral and gut microbiomes are distinct compared to other life stages, within both non-human and human models. While there is limited research in this area, the microbiome appears to be vulnerable to substance use exposure earlier in life, including substances commonly initiated and escalated during adolescence and young adulthood (i.e. alcohol, cannabis, and tobacco).

CONCLUSIONS

Studies across the lifespan indicate that adolescence and young adulthood are distinct periods of development, where the microbiome is sensitive to exposures, including substance use. There is a need for more studies focused on the adolescent and young adult microbiome and substance use, as well as focused on the oral microbiome during this developmental period. Understanding the gut and oral microbiome during adolescence and young adulthood may provide insight into the pathophysiology of substance use disorders.

Pairwise comparisons of three medication adherence outcomes in adolescents who use alcohol

BACKGROUND

Accurate assessment of medication adherence is important for understanding pharmacotherapy outcomes across all phases of adolescent substance use disorder (SUD) clinical trials. The objective of this study was to describe and assess the pairwise concordance between three commonly used non-biological medication adherence assessment methods in adolescents who use alcohol to inform the selection of medication adherence measures for use in future youth SUD trials.

METHODS

Participants (N = 32, 17-19-years-old) took N-acetylcysteine and placebo, in a randomized cross-over design, for 10 days each. Medication adherence was assessed (20 days total) via pill count, medication videos submitted twice daily, and the Medication Event Monitoring System (MEMS®). Lin's Concordance Correlation Coefficient (CCC) assessed concordance and Bland-Altman plots are reported. Linear mixed-effects models with main effects of medication, treatment block (first medication, second medication), and sequence were also run.

RESULTS

Medication videos yielded the lowest (64%) and pill count yielded the highest (89%) adherence estimates. CCC values indicated poor correspondence, except between pill count and MEMS. The Bland-Altman plots showed good pairwise agreement between all methods. Linear mixed-effects models indicated a difference between the first and second cross-over medication, with adherence estimates being lower for the second medication, regardless of whether it was N-acetylcysteine or placebo.

CONCLUSIONS

The study yielded important and practical information. First, incorporating more than one method of adherence assessment may capture estimated floor and ceiling adherence in the absence of a biological marker. This is particularly relevant for remote or hybrid studies where bio-marker collection is challenging. Selection of the assessment methods will depend on study goals. Second, the continuation of medication adherence research can benefit each phase of clinical trials and inform rigorous pharmacotherapy evaluation.

N-acetylcysteine does not alter neurometabolite levels in non-treatment seeking adolescents who use alcohol heavily: A preliminary randomized clinical trial

Current treatments for adolescent alcohol use disorder (AUD) are mainly psychosocial and limited in their efficacy. As such, pharmacotherapies are being investigated as potential adjunctive treatments to bolster treatment outcomes. N-acetylcysteine is a promising candidate pharmacotherapy for adolescent AUD because of its tolerability and demonstrated ability to modulate glutamatergic, GABAergic, and glutathione systems. The primary objective of this double-blind, placebo-controlled, within-subjects crossover preliminary investigation was to measure potential changes within glutamate + glutamine (Glx), GABA, and glutathione levels in the dorsal anterior cingulate cortex (dACC) using proton magnetic resonance spectroscopy during 10-days of N-acetylcysteine (1200 mg twice daily) compared to 10-days of placebo in non-treatment seeking adolescents who use alcohol heavily (N = 31; 55% female). Medication adherence was confirmed via video. Effects on alcohol use were measured using Timeline Follow-Back as an exploratory aim. Linear mixed effects models controlling for baseline metabolite levels, brain tissue composition, alcohol use, cannabis use, and medication adherence found no significant differences in Glx, GABA, or glutathione levels in the dACC after N-acetylcysteine compared to placebo. There were also no measurable effects on alcohol use; however, this finding was underpowered. Findings were consistent in the subsample of participants who met criteria for AUD (n = 19). The preliminary null findings in brain metabolite levels may be due to the young age of participants, relatively low severity of alcohol use, and non-treatment seeking status of the population investigated. Future studies can use these findings to conduct larger, well-powered studies within adolescents with AUD.

The lateral habenula is not required for ethanol dependence-induced escalation of drinking

The lateral habenula (LHb) is an epithalamic nuclei that has been shown to signal the aversive properties of ethanol. The present study tested the hypothesis that activity of the LHb is required for the acquisition and/or expression of dependence-induced escalation of ethanol drinking and somatic withdrawal symptoms. Male Sprague-Dawley rats completed 4 weeks of baseline drinking under a standard intermittent access two-bottle choice (2BC) paradigm before undergoing 2 weeks of daily chronic intermittent ethanol (CIE) via vapor inhalation. Following this CIE exposure period, rats resumed 2BC drinking to assess dependence-induced changes in voluntary ethanol consumption. CIE exposed rats exhibited a significant increase in ethanol drinking that was associated with high levels of blood alcohol and a reduction in somatic symptoms of ethanol withdrawal. However, despite robust cFos activation in the LHb during ethanol withdrawal, chemogenetic inhibition of the LHb did not alter either ethanol consumption or somatic signs of ethanol withdrawal. Consistent with this observation, ablating LHb outputs via electrolytic lesions of the fasciculus retroflexus (FR) did not alter the acquisition of somatic withdrawal symptoms or escalation of ethanol drinking in CIE-exposed rats. The LHb controls activity of the rostromedial tegmental nucleus (RMTg), a midbrain nucleus activated by aversive experiences including ethanol withdrawal. During ethanol withdrawal, both FR lesioned and sham control rats exhibited similar cFos activation in the RMTg, suggesting that RMTg activation during ethanol withdrawal does not require LHb input. These data suggest that, at least in male rats, the LHb is not necessary for the acquisition or expression of escalation of ethanol consumption or expression of somatic symptoms of ethanol withdrawal. Overall, our findings provide evidence that the LHb is dispensable for some of the negative consequences of ethanol withdrawal.

Brain metabolite alterations related to alcohol use: a meta-analysis of proton magnetic resonance spectroscopy studies

Alcohol misuse and alcohol use disorder (AlUD) have neurobiological consequences. This meta-analysis of proton magnetic resonance spectroscopy (MRS) studies aimed to assess the differences in brain metabolite levels in alcohol misuse and AUD relative to controls (PROSPERO registration: CRD42020209890). Hedge's g with random-effects modeling was used. Sub-group and meta-regression techniques explored potential sources of demographic and MRS parameter heterogeneity. A comprehensive literature review identified 43 studies, resulting in 69 models across gray and white matter (GM, WM). Lower N-acetylaspartate levels were found in frontal, anterior cingulate cortex (ACC), hippocampal, and cerebellar GM, and frontal and parietal WM, suggesting decreased neuronal and axonal viability. Lower choline-containing metabolite levels (all metabolites contributing to choline peak) were found in frontal, temporal, thalamic, and cerebellar GM, and frontal and parietal WM, suggesting membrane alterations related to alcohol misuse. Lower creatine-containing metabolite levels (Cr; all metabolites contributing to Cr peak) were found in temporal and occipital cortical GM, while higher levels were noted in midbrain/brainstem GM; this finding may have implications for using Cr as an internal reference. The lack of significant group differences in glutamate-related levels is possibly related to biological and methodological complexities. The few studies reporting on GABA found lower levels restricted to the ACC. Confounding variables were age, abstinence duration, treatment status, and MRS parameters (echo time, quantification type, data quality). This first meta-analysis of proton MRS studies consolidates the numerous individual studies to identify neurometabolite alterations within alcohol misuse and AUD. Future studies can leverage this new formalized information to investigate treatments that might effectively target the observed disturbances.

Acinetobacter calcoaceticus is Well Adapted to Withstand Intestinal Stressors and Modulate the Gut Epithelium

Background: The gastrointestinal tract has been speculated to serve as a reservoir for Acinetobacter, however little is known about the ecological fitness of Acinetobacter strains in the gut. Likewise, not much is known about the ability of Acinetobacter to consume dietary, or host derived nutrients or their capacity to modulate host gene expression. Given the increasing prevalence of Acinetobacter in the clinical setting, we sought to characterize how A. calcoaceticus responds to gut-related stressors and identify potential microbe-host interactions. Materials and Methods: To accomplish these aims, we grew clinical isolates and commercially available strains of A. calcoaceticus in minimal media with different levels of pH, osmolarity, ethanol and hydrogen peroxide. Utilization of nutrients was examined using Biolog phenotypic microarrays. To examine the interactions of A. calcoaceticus with the host, inverted murine organoids where the apical membrane is exposed to bacteria, were incubated with live A. calcoaceticus, and gene expression was examined by qPCR. Results: All strains grew modestly at pH 6, 5 and 4; indicating that these strains could tolerate passage through the gastrointestinal tract. All strains had robust growth in 0.1 and 0.5 M NaCl concentrations which mirror the small intestine, but differences were observed between strains in response to 1 M NaCl. Additionally, all strains tolerated up to 5% ethanol and 0.1% hydrogen peroxide. Biolog phenotypic microarrays revealed that A. calcoaceticus strains could use a range of nutrient sources, including monosaccharides, disaccharides, polymers, glycosides, acids, and amino acids. Interestingly, the commercially available A. calcoaceticus strains and one clinical isolate stimulated the pro-inflammatory cytokines Tnf, Kc, and Mcp-1 while all strains suppressed Muc13 and Muc2. Conclusion: Collectively, these data demonstrate that A. calcoaceticus is well adapted to dealing with environmental stressors of the gastrointestinal system. This data also points to the potential for Acinetobacter to influence the gut epithelium.

Cardiovascular Consequences of Excessive Alcohol Drinking via Electrocardiogram: A Systematic Review

ABSTRACT

There is a link between excessive alcohol drinking and an increased risk to develop cardiovascular disease, including alcoholic cardiomyopathy. This association warrants further research on the potential utility for the electrocardiogram (ECG) in the participatory management of the chronic consequences of alcohol use disorder (AUD). Our goal is to enhance understanding about the pernicious role alcohol plays on cardiac health using the ECG, an accessible, cost-effective, validated tool to inform novel targeted treatments for AUD. In this systematic review of human studies, we examine the relationship between abnormal clinically significant changes to ECG variables and excessive alcohol drinking with the goal of identifying key patterns specific to quantity of alcohol consumed. Three independent reviewers and one consensus reviewer, adhering to the PRISMA guidelines, conducted an initial review on studies published from database inception to April 19, 2019, using PubMed, Embase, CINAHL and COCHRANE databases. The initial search generated 2,225 articles. The final selected number included 153 original articles. This systematic review provides evidence of patterns of clinically significant changes to ECG variables as a consequence of excessive alcohol consumption. Future directions include investigating whether a real-time assessment, such as the ECG, in conjunction with other key behavioral and cardiac measures, can help clinicians and patients realize the progressive and insidious cardiac damage because of excessive alcohol consumption. This theory-guided nurse science review supports the development of personalized symptom monitoring to deliver tailored feedback that illuminate risk factors as a potentially transformative approach in the management of AUD.

Leptin Gene and Leptin Receptor Gene Polymorphisms in Alcohol Use Disorder: Findings Related to Psychopathology

Comorbidity between alcohol use disorder (AUD) and other addictive and psychiatric disorders is highly prevalent and disabling; however, the underlying biological correlates are not fully understood. Leptin is a peptide hormone known for its role in energy homeostasis and food intake. Furthermore, leptin plays a key role in the activity of the hypothalamic-pituitary-adrenal (HPA) axis and of several neurotransmitter systems that regulate emotionality and behavior. However, human studies that have investigated circulating leptin levels in relation to AUD and affective disorders, such as anxiety and depression, are conflicting. Genetic-based analyses of the leptin gene (LEP) and leptin receptor gene (LEPR) have the potential of providing more insight into the potential role of the leptin system in AUD and comorbid psychopathology. The aim of the current study was to investigate whether genotypic variations at LEP and LEPR are associated with measures of alcohol use, nicotine use, anxiety, and depression, all of which represent common comorbidities with AUD. Haplotype association analyses were performed, using data from participants enrolled in screening and natural history protocols at the National Institute on Alcohol Abuse and Alcoholism (NIAAA). Analyses were performed separately in European Americans and African Americans due to the variation in haplotype diversity for most genes between these groups. In the European American group, one LEP haplotype (EB2H4) was associated with lower odds of having a current AUD diagnosis, two LEPR haplotypes (EB7H3, EB8H3) were associated with lower cigarette pack years and two LEPR haplotypes (EB7H2, EB8H2) were associated with higher State-Trait Anxiety Inventory (STAI-T) scores. In the African American group, one LEP haplotype (AB2H8) was associated with higher cigarette pack years and one LEP haplotype (AB3H2) was associated with lower Fagerström Test for Nicotine Dependence (FTND) scores. Overall, this study found that variations in the leptin and leptin receptor genes are associated with measures of alcohol use, nicotine use, and anxiety. While this preliminary study adds support for a role of the leptin system in AUD and psychopathologies, additional studies are required to fully understand the underlying mechanisms and potential therapeutic implications of these findings.

Effects of exogenous ghrelin administration and ghrelin receptor blockade, in combination with alcohol, on peripheral inflammatory markers in heavy-drinking individuals: Results from two human laboratory studies

The ghrelin system has been garnering interest for its role in different neuropsychiatric disorders, including alcohol use disorder (AUD). Accordingly, targeting the ghrelin system is under investigation as a potential novel therapeutic approach. While alcohol provokes the immune system and inflammatory responses, ghrelin has potent immunomodulatory and anti-inflammatory properties. The present study aimed to shed light on the "crosstalk" between ghrelin and inflammation by examining the effects of exogenous ghrelin administration and ghrelin receptor blockade on peripheral inflammatory markers in the context of two human laboratory studies with alcohol administration. Non-treatment-seeking, heavy-drinking individuals with alcohol dependence, the majority of whom were African American males, were enrolled. In the first randomized, crossover, double-blind, placebo-controlled human laboratory study, participants underwent two experimental paradigms - an intravenous alcohol self-administration (IV-ASA) and an intravenous alcohol clamp (IV-AC) - each consisting of two counterbalanced sessions (ghrelin, placebo). A loading dose of intravenous ghrelin (3 mcg/kg) or placebo, followed by a continuous ghrelin (16.9 ng/kg/min) or placebo infusion was administered. In the second dose-escalating, single-blind, placebo-controlled human laboratory phase 1b study, participants were dosed with an oral ghrelin receptor blocker (PF-5190457) and underwent an oral alcohol challenge. Repeated blood samples were collected, and plasma concentrations of the following inflammatory markers were measured: C-reactive protein (CRP), interleukin (IL)-6, IL-10, IL-18, and tumor necrosis factor alpha (TNF-α). During the IV-ASA experiment, significant drug × time interaction effects were observed for IL-6 (F_3,36 = 3.345, p = 0.030) and IL-10 (F_3,53.2 = 4.638, p = 0.006), indicating that ghrelin, compared to placebo, significantly reduced blood concentrations of the proinflammatory cytokine IL-6, while increasing blood concentrations of the anti-inflammatory cytokine IL-10. No significant drug × time interaction effects were observed during the IV-AC experiment, possibly because of its much shorter duration and/or smaller sample. Treatment with PF-5190457, compared to placebo, had no significant effect on the inflammatory markers investigated. In conclusion, a supraphysiologic pharmacological challenge with exogenous ghrelin in heavy-drinking individuals produced anti-inflammatory effects in the context of intravenous alcohol administration. On the contrary, ghrelin receptor blockade did not lead to any change in the inflammatory markers included in this study. Mechanistic studies are required to better understand the interaction between ghrelin, alcohol, and inflammatory processes.