Drug and Alcohol Dependence

Background and Aims: The North American overdose crisis is increasingly characterized by complex polysubstance use alongside a transition from injecting to smoking unregulated opioids. However, transitions involving multiple substances remain understudied. We characterized longitudinal transitions in the route of administration and frequency of heroin, fentanyl, and methamphetamine use and examined whether these transitions differed by multilevel factors hypothesized to influence patterns of polysubstance use and routes of administration over time. Design: People who inject drugs (PWID) enrolled in a cohort study completed baseline surveys (October 2020-2021) and three biannual follow-up visits (through April 2023). Setting: San Diego, California, and Tijuana, Baja California. Participants: Among 612 PWID, median age was 43 years; most were male (74%), Hispanic, Latino, or Mexican (72%), and San Diego residents (67%). Measurements: Based on past six-month substance use behaviors reported at each visit, we categorized participants according to six indicators over time: low- (< weekly) and high-frequency ([&ge;] weekly) smoking and injecting of heroin, fentanyl, and methamphetamine. We then used latent transition analysis (LTA) to identify distinct subgroups of participants with respect to these indicators at baseline and examine transitions between them over 18 months. We fit models with 2-5 subgroups, selecting the final model based on fit and interpretability and used multiple-groups LTA to examine differences in subgroup transitions by multilevel factors. Findings: We identified four subgroups: Subgroup 1 (Heroin-Methamphetamine Polyroute), characterized by high-frequency heroin and methamphetamine smoking and injection, included 22% of participants at baseline but 0% at 18 months. Subgroup 2 (Methamphetamine-dominant Smoking), characterized by high-frequency methamphetamine smoking, accounted for 14% of participants at baseline and 18 months. Subgroup 3 (Fentanyl-Methamphetamine Smoking), characterized by high-frequency fentanyl and methamphetamine smoking, included 4% of participants at baseline and 21% at 18 months. Subgroup 4 (Heroin-dominant Injecting), characterized by high-frequency heroin injection, included 61% of participants at baseline and 65% at 18 months. Participants in Subgroup 1 primarily transitioned to Subgroups 3 and 4 over time. Larger increases in Subgroup 3 prevalence occurred for participants who, at baseline, experienced homelessness, resided in San Diego (vs. Tijuana), received syringes from a syringe services program, and overdosed in the past six months. Conclusions: PWID in this region increasingly transitioned from high-frequency heroin and methamphetamine injection toward fentanyl and methamphetamine smoking, likely reflecting shifts in drug availability. Results highlight the need for multilevel interventions that address health harms resulting from polysubstance smoking alongside continued injection.

BackgroundEvidence suggests steeper accelerating opioid-related overdose, and non-medical use rates, in middle aged men in recent years compared with younger cohorts. Little is known about whether this is driven by age-related differences in the effects of opioids compared with socio-cultural factors driving non-medical consumption. Rodent models can be useful for dissociating biological from psychosocial factors, however, only minimal evidence exists on the effects of opioids in middle-age rats. ObjectiveTo determine if the anti-nociceptive and rewarding effects of opioids differ between adult and middle-age rats. MethodsFemale and male Wistar rats were obtained in early adulthood and examined across 4 to 11 months of age for nociceptive responses to heroin (0-1.56 mg/kg, s.c.) using a warm-water tail withdrawal assay. Subgroups (N=8 per group) were initiated on intravenous self-administration (IVSA) of heroin at either 5 months or 12 months of age. ResultsAnti-nociceptive effects of heroin did not differ across age. Female rats that initiated IVSA in early adulthood or middle-age obtained significantly more infusions of heroin than male rats of the same age during acquisition, and in dose-substitution under a FR1 schedule. Male, but not female, rats that initiated IVSA in middle age self-administered less heroin then rats that initiated in early adulthood; this was observed in acquisition and in dose-substitution. DiscussionThis study shows that opioid reward is diminished in middle aged male rats. It also found that middle age rats can be used effectively to model opioid-related outcomes, including drug seeking using the IVSA procedure.

Aims and SettingIn the U.S., the emergence of new adulterants and novel psychoactive substances continues to complicate approaches to overdose, treatment, and public safety. Information about this changing drug supply is often gleaned from police drug seizures, but community drug checking services, which test the contents of a persons drug supply and share that data, provide another means to understand local drug supplies. However, it is unclear how seized drugs differ from those collected in the community, whether one approach is potentially more instructive, and what can be learned about local drug supplies from each source. We therefore compared drug samples tested from police departments (PDs) and community partner (CP) drug checking programs to examine what, if any, differences existed in sample content, form, submitter characteristics, and emerging substance presence. DesignWe conducted a retrospective cohort analysis of drug samples collected and tested between April 2018 and December 2025 by the Massachusetts Drug Supply DataStream derived from CPs and PDs operating in the same geographic area across eight locations. Bivariate analyses (Chi-square, Fishers exact) tested for differences in sample and submitter characteristics by source. FindingsThere were 2,430 unique samples submitted by CPs (68.1%) and PDs (31.9%) from the same location. Compared to CP samples, proportionally more PD samples showed fentanyl as primary substance (74.2% PD vs. 64% CP, p<.001) and less often contained additives (xylazine 15.0% PD vs. 27.4% CP; medetomidine 0.6% PD vs. 2.2% CP, both p<.001). PD samples were typically powders (73.2% vs. 37.9%) and pills (13.6% vs. 3.6%) while CP samples were more often residue (51.9% vs. 2.1%, p<.001). Submitter characteristics, when reported, differed by source: gender (n=528, male: 78.6% PD vs. 50.1% CP, p<.001), race/ethnicity (n=468, Black: 15.8% PD vs. 7.8% CP; Hispanic: 6.7% PD vs. 13.2% CP, p<.05), and associated overdose (n=242, fatal: 62.9% vs. 10.9%, p<.001). Emergent substances were detected a median of 249 days sooner in CP than co-located PD samples, though drugs exhibiting concerning patterns (e.g., unexpected fentanyl in stimulants) had similar, swift detection times. ConclusionDrug samples differ based on PD vs. CP source in significant ways that may introduce bias when drawing conclusions about drug supply trends but also offer unique insights for public health and responses to emerging drugs. Modern drug monitoring should include a broad range of sources to best prepare for changes the illicit supply may bring to overdose prevention, public safety, and health systems.

BackgroundIntravenous self-administration (IVSA) of opioids by rats has been shown frequently to exhibit no sex differences, in many cases a higher intake of females, and only rarely higher rates in males. A diversity of methodological parameters (opioid identity, training doses, rat strain, session duration) makes it difficult to identify consistent contributions to these outcomes. ObjectiveTo determine if Heterogeneous Stock (HS) rats derived from 8 founder strains differ by sex in the IVSA of opioids. MethodsMale and female Heterogeneous Stock (N=7-8 per sex) rats were permitted to self-administer heroin (20 {micro}g/kg/infusion) in 2 hour sessions under a Fixed Ratio 1 schedule of reinforcement. After acquisition, animals completed sessions in which different infusion doses of heroin (0, 15, 30, 60, 120 {micro}g/kg/infusion), oxycodone (0, 30, 60, 150, 300 {micro}g/kg/infusion) and fentanyl (0, 0.625, 1.25, 2.5, 5.0 {micro}g/kg/infusion) were assessed. Next, animals were evaluated on doses of heroin (15, 30, 60, 120 {micro}g/kg/infusion), oxycodone (30, 60, 150, 300 {micro}g/kg/infusion) and fentanyl (0.625, 1.25, 2.5, 5.0 {micro}g/kg/infusion) under a Progressive Ratio schedule. Anti-nociceptive effects of heroin (0.56-2.4 mg/kg, s.c.) were examined with a warm water tail-withdrawal assay. ResultsFemale HS rats consistently self-administered more infusions of opioids, including heroin during acquisition, all three opioids during FR-1 dose substitution and of oxycodone and fentanyl in the PR procedure. Male rats were moderately more sensitive to the anti-nociceptive effects of heroin. ConclusionsFemale rats drawn at random from a genetically diverse population self-administer opioids at higher rates than their male counterparts.

PurposeOpioid overdose deaths disproportionately affect racial and ethnic minority populations in the United States, yet claims-based evidence characterizing the multi-dimensional structure of these disparities across incidence, treatment access, costs, and insurance coverage remains limited. MethodsWe conducted a retrospective cross-sectional and longitudinal cohort analysis using the HealthVerity Launch Sample, a large administrative claims database. The study population comprised 3,675,823 patients across 5 racial groups enrolled between 2020 and 2024. Eight primary analyses were conducted, including age-sex standardized overdose rates, temporal disparity trends, medication-assisted treatment (MAT) receipt, naloxone access, pharmacy costs, insurance payer type, care setting, and multivariable logistic regression for overdose risk. ResultsBlack patients had the highest age-sex standardized overdose rate (363.4 per 100,000; rate ratio [RR] = 1.27 vs. White), and those with opioid use disorder (OUD) received MAT at a rate 35% lower than White patients (19.8% vs. 30.7%; RR = 0.645), driven primarily by a buprenorphine access deficit. AIAN patients demonstrated consistent multi-dimensional disadvantage across naloxone access, MAT engagement, and pharmacy costs. After adjustment for payer type, age, and sex, all non-White groups showed lower adjusted odds of overdose than White patients (Black OR = 0.87; AIAN OR = 0.25), with Medicaid enrollment carrying 7.06 times the overdose odds of commercial insurance. ConclusionInsurance type is the dominant predictor of overdose risk, and the disproportionate Medicaid enrollment of Black patients is both a consequence of structural disadvantage and access disparities. Targeted interventions such as buprenorphine expansion in Medicaid and enhanced naloxone distribution are recommended.

Background and Aims: Synthetic opioids cause tens of thousands of deaths each year in North America, and there are indications that synthetic opioids are also becoming increasingly prevalent in the European drug market. This study aimed to examine high-risk substance use in the German drug-using community with a particular focus on the synthetic opioids fentanyl and nitazenes and related awareness, concerns, overdose experiences, and harm-reduction behavior. Design: Cross-sectional, observational online survey. Setting: Open drug-use scenes, addiction clinics, and substitution practices at numerous geographic locations throughout Germany, August to September 2025. Participants: 235 individuals aged 14+ from the drug using community (mean age 43.4 years; 57.9% male), 79.6% recruited by peers in open drug-use scenes. Measurements: The primary outcome was substances used within the past 12 months. In addition, sources, forms, routes of administration, and perceived changes in availability and price of (synthetic) opioids were assessed as well as risk perceptions, fears, harm-reduction behavior, and overdose-related experiences. Findings: 227 respondents reported substance use with an average of 6.2 substances, and 73.1% (95% confidence interval [CI] = 67.0-78.5%) had used at least one opioid in the past year. Synthetic opioids were consumed in many parts of Germany and across all age and gender groups. Among participants who experienced a shortage of their primary opioid in the past year, 25% (95% CI = 15.8-37.2%) reported having used fentanyl instead. 56.5% (95% CI = 36.8-74.3%) of individuals using synthetic opioids reported having experienced an overdose in the past twelve months. Most of the respondents perceived synthetic opioids as posing a high risk, and a substantial proportion expressed fear that they could be mixed into their own substances. However, only 9.9% (95% CI = 6.6-14.7%) use drug checking, although the vast majority stated they would use it if it were available to them. Conclusions: Synthetic opioids, including fentanyl and nitazenes, have entered the German drug scene, with users reporting high rates of overdose and limited access to harm reduction measures. Germany may be in an early phase of a synthetic opioid transition, warranting urgent expansion of surveillance, naloxone distribution, and drug checking services.

ObjectivesTo evaluate the effectiveness and cultural feasibility of family-supervised disulfiram as a first-line treatment for alcohol use disorder (AUD) in Sri Lanka, and to compare its clinical outcomes with standard therapy delivered at a tertiary psychiatric unit. DesignSingle-blind Randomized Controlled Trial known as ETAT-RCT (Efficacy of Two Alcohol Treatments) was conducted under routine clinical setup with three parallel groups: family-supervised disulfiram, locally developed psychosocial intervention, and routine treatment. Allocation was independently concealed; assessors were blinded. Analyses followed an intention-to-treat approach using repeated-measures ANOVA (group x time). This paper reports the disulfiram (test) versus routine treatment (control) comparison; the psychosocial intervention will be reported separately. SettingUniversity Psychiatry Unit, National Hospital of Sri Lanka, Colombo (UPU, NHSLC). ParticipantsPatients aged [&ge;]14 years with AUD presenting to the unit were recruited consecutively without inducements. Planned allocation ratio was 1:1:1 with 31 participants per arm; key exclusions were lifetime psychotic disorder and current contraindication to disulfiram. RandomisationParticipants were randomised into each treatment arm using an independent concealed paper-based allocation system. Intervention(1) family-supervised disulfiram, with psychoeducation/support only - DT arm, (2) a locally developed denormalization focused psychosocial programme - PT arm, and (3) standard therapy (motivational/cognitive/behavioural input; naltrexone permitted; no disulfiram/denormalisation) - ST arm. Outcome measuresPrimary outcome was Alcohol Use Disorders Identification Test (AUDIT) score at 12 months. Key secondary outcomes were past 30 day alcohol use via Timeline Follow-Back (TLFB); alcohol biomarkers [ALT (alanine aminotransferase), {gamma}-GT (gamma-glutamyl transferase), MCV (mean corpuscular volume)]; locally developed measures of addiction-relevant cognitive, affective, behavioural factors [AARSU (Attitude Assessment Related to Substance Use), BARSU (Behaviour Assessment Related to Substance Use)]; and Quality of Life Enjoyment and Satisfaction Questionnaire Short Form (Q-LES-Q-SF). Outcomes were assessed at baseline, 6, and 12 months. ResultsParticipants in DT (n=33) and ST (n=38) were comparable at baseline. Both groups showed clinically and statistically significant improvement in AUDIT scores over 12 months (DT: F=39.90, p<0.001; ST: F=49.90, p<0.001), with no groupxtime interaction (F<0.001, p=0.98). Biomarkers and AARSU, and BARSU and Q-LES-Q-SF to a lesser degree, mirrored the AUDIT pattern. TLFB did not change significantly over time in either arm (p>0.05). In moderator analyses, improvement in AUDIT was not moderated by baseline motivation (F=0.20, p=0.89) but was moderated by baseline AUD severity (F=7.70, p=0.007). No serious adverse events were attributed to disulfiram. Adherence to supervised dosing was generally high during periods of supervision but intermittent overall. ConclusionsIn this pilot RCT, family-supervised disulfiram achieved 12-month outcomes comparable to standard therapy in a tertiary Sri Lankan setting. Improvements were independent of baseline motivation and varied by baseline AUD severity. These findings may support family-supervised disulfiram as a culturally feasible first-line option in Sri Lanka; larger, adequately powered multicentre trials are warranted to confirm effectiveness and scalability. Trial registrationSLCTR/2014/021 Strengths and limitations of this studyO_LIThis pragmatic randomised controlled trial demonstrates an improved real world applicability and validity as it was conducted in an unmodified public-sector psychiatric setting. C_LIO_LIStrong generalisability of the study with similar health systems due to broad eligibility criteria of patients warranted the inclusion of regular and general patient cohort with alcohol use disorders, strengthening generalisability within similar health systems. C_LIO_LIInterventions were carried out without additional staff or patient monitoring reflecting routine clinical practice. C_LIO_LIComprehensive assessment beyond abstinence alone with multidimensional outcomes such as alcohol related harm, biomarkers, cognitive behavioural change and quality of life. C_LIO_LIMinor potential in performance bias due to the nature of intervention where blinding study subjects and clinicians is not feasible. C_LIO_LISampling bias towards males and variability within the ST arm can affect the generalisability. C_LI

BackgroundDrug checking services (DCS) promote drug supply awareness among people who use drugs (PWUD) by detecting adulterants such as fentanyl and xylazine that are associated with overdose morbidity and mortality. However, there is limited research on DCS implementation in Latin America (LA). MethodsWe conducted a survey of 38 DCS across LA (n=10) and the US (n=28) and compared program characteristics and barriers between these two regions. We also conducted a focus group discussion (FGD) with staff representing six organizations implementing DCS in LA. FGD themes were mapped to constructs quantitatively assessed in the survey. ResultsCompared to US DCS, LA DCS more frequently reported funding gaps as a major implementation barrier (80% vs. 54%), law enforcement confiscating DCS supplies (38% vs. 11%), as well as offering supervised drug consumption (30% vs. 4%) and mental health/counseling (40% vs. 18%), but less frequently reported that DCS equipment was legal (44% vs. 75%). DCS on the Mexico-US border focused on people who inject drugs and offered syringe services, supervised consumption, and rapid sexually transmitted infection testing. DCS in central Mexico, Colombia, Peru, and Chile primarily provided DCS for the nightlife community (e.g., attendees of concerts/raves). Barriers to DCS implementation cited by FGD discussants included inadequate funding, DCS legal ambiguities, lack of government support, and cartel violence. ConclusionDCS in LA would benefit from increased funding, government support, and a more permissive legal environment, thereby strengthening harm reduction efforts and improving safety for PWUD.

Background: Alcohol use disorder (AUD) is marked by high relapse rates often driven by craving, yet less is known about whether in vivo, social, and place-based alcohol cues are differentially associated with craving across affective states. This study examined independent and affect-contingent associations of these cues with momentary craving in adults with AUD enrolled in an alcohol intervention study. Methods: Thirty-three adults with AUD completed up to four daily ecological momentary assessments (EMA) for 28 days. EMA prompts assessed craving, in vivo alcohol exposure, being around usual drinking partners, being in usual drinking places, and high-arousal positive affect (PA) and negative affect (NA). Multilevel mixed-effects models adjusted for demographics, intervention phase (1 = post, 0 = pre), AUD severity, and temporal and contextual covariates. Results: EMA compliance was high (median per-participant = 86.6%). Within-person elevations in in vivo alcohol exposure and being around usual drinking partners were independently associated with greater momentary craving, whereas being in usual drinking places was not. In vivo alcohol exposure was more strongly associated with craving during higher-than-usual PA ({beta} = 0.08, p = .032), whereas being in usual drinking places was more strongly associated with craving during higher-than-usual NA ({beta} = 0.06, p = .036), adjusting for intervention phase, which was associated with lower craving. Conclusions: Findings support the need for personalized just-in-time adaptive interventions tailored to high-risk, momentary cue-affect contexts in AUD, beyond low-frequency clinician-delivered feedback that may reduce average craving but not fully address real-time risk. ClinicalTrials.gov registration: NCT05135767.

BackgroundThe mechanisms underlying pharmacological treatments for stimulant use disorders are poorly understood. This study examined whether changes in craving, depressive symptoms, and/or impulsivity mediate treatment effect in pharmacotherapy with combined naltrexone and bupropion for methamphetamine use disorder. MethodsThe study was based on secondary analysis of data from the Accelerated Development of Additive Pharmacotherapy Treatment for methamphetamine disorder (ADAPT-2) trial which randomized adults with methamphetamine use disorder to combined treatment with injectable naltrexone (380 mg every three weeks) plus oral bupropion (450 mg daily) versus placebo. A total of 403 adults with methamphetamine use disorder participated in the first Stage; 225 of first Stage participants in the placebo arm who did not respond to treatment were re-randomized in the second Stage. Mediation effects were examined using longitudinal multi-level structural equation modeling. ResultsNaltrexone-bupropion treatment was associated with decreases in drug use, craving, depressive symptoms, and impulsivity. The indirect effect of treatment through change in craving was significant (self-reported use=-0.21, 95% Credible Interval [CrI]=-0.35, -0.09; drug screen-ascertained use=-0.36, 95% CrI=-0.63, -0.16). Change in craving mediated 56% of the treatment effect on self-reported use and 45% of the effect on drug screen-ascertained use. Estimates for mediated effects for depressive symptoms and impulsivity were smaller in magnitude and non-significant. ConclusionReduction in craving mediates the effect of naltrexone-bupropion pharmacotherapy in methamphetamine use disorder. Craving may serve as a surrogate measure of treatment efficacy in short-term trials and help identify promising candidate medications to be tested in larger and longer-term trials. Trial RegistrationClinicalTrials.gov number: NCT03078075.

RationaleThe progression of psychostimulant abuse is associated with a shift from recreational to habitual use (R2H-shift). Because this R2H-shift can be modeled using behavioral economics, we developed a novel Behavioral Economic model for the Analysis of Self-administration Time-curve (BEAST) to obtain R2H-shift variable(s). The relationship(s) between R2H-shift variables and drug intake (under normal and/or punishment conditions) is/are unknown. Our goal was to determine if the R2H-shift variable and intake variables obtained during the initial self-administration training phase were related to 1) drug intake at that time, and subsequent drug intake under 2) normal, 3) punishment, 4) post-punishment, and 5) price-constrained conditions. MethodLong Evans rats self-administered methamphetamine (METH, males n = 16, females n = 14), sucrose (males n = 22, females n = 22) and/or saline (males n = 3, females n = 10) under FR1 for 6 h per day for 20 days to obtain 1) followed by the assessment of subsequent drug intake under different conditions (2-5 above). We obtained all variables referenced above. We determined the relationships between all variables (multivariate analysis). ResultsThere were no sex differences detected in the METH and sucrose studies. For METH and sucrose, prior drug intake levels could predict drug intake under normal/punishment but not under price-constrained conditions. The R2H-shift variable could predict drug intake under a consumption-price curve but could not predict intake under normal/punishment conditions. ConclusionsWhile related to economic demand, the recreational-to-habitual shift rate was unrelated to drug intake levels (under normal and punishment conditions).

Pregnant and postpartum people who use drugs in the United States are trying to survive at the intersection of two of the gravest public health crises of the 21st century US: epidemics of (1) maternal mortality and (2) the overdose epidemic. Although extensive evidence documents racial/ethnic disparities in each of these epidemics separately, comparatively little research has characterized racial/ethnic patterns in their collision, that is, in maternal overdose mortality. We analyzed individual-level mortality records from the National Vital Statistics System (NVSS) for 2016-2022 to describe racial/ethnic disparities in pregnancy-associated overdose deaths (PA-OD) and pregnancy-associated substance use disorder-related deaths (PA-SUD). Racial/ethnic-specific mortality rates were calculated per 100,000 live births with exact Poisson confidence intervals. Temporal trends were summarized using annual percent change (APC), and disparities were quantified using rate ratios and differences relative to non-Hispanic White individuals. Overdose-related maternal mortality increased substantially during the study period across multiple racial and ethnic groups. Rates increased nearly threefold among non-Hispanic White individuals and rose more steeply among non-Hispanic Black individuals, producing a Black-White disparity that emerged over time. Rates among Hispanic individuals remained lower but increased rapidly, while estimates among American Indian and Alaska Native individuals were often high but unstable because of small counts. Substance use disorder-related maternal mortality exhibited a pronounced surge during 2019-2021 across several racial and ethnic groups. These findings highlight rapidly evolving racial/ethnic patterns in maternal overdose mortality and underscore the need for targeted prevention and harm-reduction strategies to reduce overdose-related deaths during pregnancy and the postpartum period. FundingWe are grateful to the following NIH grants for supporting this research: U54HD113292 and R01DA059182.

AimsTo examine the longitudinal dynamic interactions of craving and drug use in the course of treatment of stimulant use disorders. DesignCross-lagged residual dynamic structural equation modeling (R-DSEM) was used to examine the reciprocal (bidirectional) longitudinal associations between craving and drug use. SettingPooled data from 11 randomized controlled trials of pharmacotherapies for methamphetamine and cocaine use disorders in the United States sponsored by the National Institute on Drug Abuse. Participants1,936 adults with cocaine or methamphetamine use disorder. MeasurementsCraving was measured using Brief Substance Craving Scale (BSCS), drug use was measured using Timeline Followback and urine drug screen (UDS). FindingsCraving and stimulant drug use were dynamically associated over time (within-person association). Daily craving significantly predicted drug use in subsequent days (estimate=0.092, 95% credible interval [CrI]=0.081, 0.103 for self-reported drug use and estimate=0.081, 95% CrI=0.069, 0.095 for UDS-ascertained drug use). In turn, drug use predicted subsequent craving (estimate=0.361, 95% CrI=0.325, 0.398 and estimate=0.060, 95% CrI=0.028, 0.094, respectively). There was substantial between-person heterogeneity in these cross-lagged effects, as reflected in the coefficients of variation ranging from 0.78 to 2.88. ConclusionsThere is a bidirectional interaction between stimulant drug craving and drug use. The heterogeneity in the interaction of craving with stimulant drug use may partly explain between-person variability in responses to anti-craving medications in treatment of stimulant use disorders.

ObjectivesTo examine the extent to which heat-related causes of death are recorded in fatal drug overdoses, how these patterns vary across states and over time, and how overdose characteristics differ between deaths with, versus without, heat involvement recorded. MethodsDeath certificate data for all drug overdose deaths in US residents from 2001 to 2024 (from the National Center for Health Statistics) were analyzed to identify whether a heat-related cause of death was also listed on the death certificate. Joinpoint regression, descriptive statistics, and nonparametric tests were used to examine temporal trends and compare overdose deaths with versus without recorded heat involvement. ResultsIn 2001, fewer than 10 drug overdose deaths with recorded heat involvement were identified, but this number increased to 558 in 2024. From 2013 to 2024, mortality rates increased significantly, with an estimated annual percent change of 30.1 (95% Confidence Interval, 26.5-47.1). The highest mortality rates and numbers of deaths were observed in residents of Arizona and Nevada. American Indian/Alaska Native, Mexican-heritage, and foreign-born populations accounted for larger shares of overdose deaths with, compared to without, heat involvement recorded. A street or highway was more frequently identified as the place of injury in overdose deaths with (18.9%), versus without (2.2%) heat involvement reported. Psychostimulants such as methamphetamine were involved in 85.9% of overdose deaths with, compared to 28.9% without, recorded heat involvement. ConclusionsAlthough representing only a fraction of all overdose deaths, fatal overdoses involving heat exposure have increased markedly over time and disproportionately impact certain states and demographic groups.

BackgroundThe Adolescent Brain Cognitive Development (ABCD) Study(R) offers rich longitudinal data on environmental, genetic, and other factors related to substance use initiation. Classical marginal structural models (MSMs) require selecting covariates for propensity models, which is challenging in the presence of hundreds of correlated predictors. MethodsWe analyzed longitudinal panel data from 11,868 ABCD participants, where each individual contributed repeated observations over time. Interval-level binary outcomes were defined for initiation of alcohol, nicotine, cannabis, and any substance, restricting analyses to participants at risk prior to initiation. All predictors were constructed as lagged variables to preserve temporal ordering. We implemented a two-stage machine learning-based causal framework. First, we performed graph discovery using a Granger-inspired lagged predictive modeling approach, applying elastic-net logistic regression to identify predictive relationships between lagged environmental variables and future initiation outcomes. Robust candidate edges were selected using subject-level bootstrap stability selection. Second, we estimated adjusted effect sizes for stable edges using double machine learning (DML)-style partialling-out with cross-fitting. For each candidate predictor, the treatment was defined as the lagged variable of interest and adjusted for high-dimensional lagged covariates. Cross-fitting with group-based splitting accounted for within-subject dependence, and nuisance functions were estimated using random forest models. Cluster-robust standard errors were used for inference. ResultsWe identified a set of stable predictors across multiple domains, including sleep patterns, family environment, peer relationships, behavioral traits, and genetic risk. Many predictors were shared across substance outcomes, while some were outcome-specific. Estimated effect sizes were modest, typically ranging from -0.01 to 0.02 per standard deviation increase in the predictor. Both risk-increasing and protective associations were observed. Risk factors included sleep disturbance and behavioral risk indicators, while protective factors included parental monitoring and structured environments. ConclusionsThis study provides a practical framework for analyzing high-dimensional longitudinal data and identifying time-varying predictors of substance use initiation. The approach combines machine learning for variable selection with causal inference methods for effect estimation. The results highlight both shared and substance-specific risk factors and identify modifiable targets, such as family environment and sleep, that may inform prevention strategies.

Current treatments for opioid use disorder (OUD) have major barriers to access. As such, researching new potential therapies for OUD is important to public health. Previous research has implicated glucagon-like peptide-1 (GLP-1) receptor agonists in decreasing the use of addictive substances by animals. In this study, female Wistar rats (N=32) were surgically implanted with jugular catheters and trained to self-administer fentanyl at a fixed-ratio 1 (FR1) schedule of reinforcement for 21 sessions under short- (ShA; 1 hour) or long-access (LgA; 8 hours) conditions. Next, the animals received injections of semaglutide (0.1 mg/kg, s.c.) or saline (0.9% NaCl, s.c.) prior to another FR1 session. The animals underwent a progressive ratio (PR) schedule of reinforcement while receiving saline (i.v.) or fentanyl (0.625-10 {micro}g/kg/inf, i.v.) and semaglutide (0.1 mg/kg, s.c.) or saline (s.c.). Next, the animals underwent a semaglutide (0-0.1 mg/kg, s.c.) dose response procedure at FR1 and a single dose of fentanyl (2.5 {micro}g/kg/inf, i.v.). Following drug discontinuation, spontaneous locomotor activity and withdrawal-like symptoms were measured. Semaglutide dose-dependently decreased fentanyl rewards under ShA and LgA conditions (p<0.05). Under a PR, semaglutide significantly decreased breakpoint (p<0.05), suggesting semaglutide decreases motivation to self-administer fentanyl. Semaglutide-treated ShA animals displayed significantly less withdrawal-like behavior (p<0.05) but not LgA animals. Overall, these findings suggest semaglutide may modulate motivation to seek opioid reward and could be useful in the development of pharmacotherapies to address OUD.

Background and AimsOn April 1st, 2024, Germany implemented the Act on the Handling of Cannabis for Non-Medical Use (KCanG), allowing adults to cultivate and possess recreational cannabis. We assessed whether this policy shift was associated with a change in the prevalence of cannabis use in the general population and in daily or almost daily cannabis use. DesignA series of 21 repeated cross-sectional surveys conducted between April/May 2022 and October/November 2025 (covering the period approximately two years before and one and a half years after the KCanG). SettingPopulation of Germany. ParticipantsA total of 32,991 people aged 14-64 years, including 2,092 (6.3%) people who used cannabis in the past 12 months. MeasurementsPast 12-month cannabis use (at least once). In past 12-month users: daily or almost daily use. To test a potential change in prevalence following the KCanG, we used piecewise binomial logistic regression models using the exact date of each wave as the predictor variable, allowing for a change in the slope at the first full wave after implementation of the KCanG in April 2024, with a random effect for wave. We conducted this analysis for the total sample as well as stratified by gender (male vs. female), age (14-24 vs. 25-64 years), and for daily or almost daily cannabis use in the subgroup of people who used cannabis in the past 12 months. Sensitivity analyses used alternate intervention dates (in-time placebo tests). FindingsThe prevalence of cannabis use and the share of (almost) daily users among 12-month users remained largely stable before and after the law reform. None of the slope coefficients before the introduction of the KCanG were statistically significant (all p [&ge;] .08), and none of the coefficients for the change in the slope were statistically significant (all p [&ge;] .31). Results of sensitivity analyses confirmed the stable trends for both outcomes. ConclusionsThe legislation of cannabis introduced in Germany in April 2024 was not associated with a change in trends of 12-month cannabis use prevalence early (1.5 years) after implementation, and also not with a change in the proportion of heavy users among past-12-month users. We recommend continued close monitoring of trends using multiple data sources and over a longer post-implementation period, as the effects of the legislation may not have fully unfolded yet.

IntroductionCurrent best practice is for primary care physicians (PCPs) to screen patients for problematic substance use at checkups. However, this practice is not routine, is done in an unstandardized manner, and contributes to the overburdening of PCPs. Screening practices also target current, potentially problematic use behaviors, thus limiting their capacity to help patients prevent problems before they start. Recent scientific advances in identifying people at high risk for substance use problems as a means of facilitating prevention efforts have not yet been integrated into medical practice. To address these issues, our research team developed a freestanding platform called the Comprehensive Addiction Risk Evaluation System (CARES). CARES provides personalized information about genetic and behavioral/environmental risk for substance use disorder (SUD) and connects individuals to resources based on their risk profile. The present study evaluated the potential for adoption and implementation of CARES within a health care system through qualitative interviews with key stakeholders. MethodsSemi-structured interviews were developed using the Consolidated Framework for Implementation Research (CFIR) and conducted with N=15 interviewees. Transcripts were analyzed using rapid qualitative analysis. ResultsKey themes included perceived need for new SUD screening tools, current SUD screening procedures and their pros/cons, openness to new ideas and clinical tools, fit of CARES with organizational goals and priorities, considerations for use of CARES with adolescent populations, anticipated patient response to CARES, barriers to implementation and uptake of CARES, changes required for implementation, and possibility for medical record integration. Interviewees generally expressed need for new screening tools and openness to using new tools, but expressed concern that existing provider burden, lack of SUD knowledge, and discomfort/stigma could stymie efforts to implement CARES. Conclusions.There is a clear need for a low-burden, easy-to-use tool for substance use screening. CARES appears to be an acceptable and feasible approach to fill this gap. These findings will be used to inform pilot implementation of CARES in a clinical care setting.

Tobacco use disorder is a chronic condition characterized by compulsive nicotine use, withdrawal, and relapse following abstinence. Impulsivity contributes to persistent nicotine use and poor cessation outcomes. This study examined whether nicotinic acetylcholine receptor (nAChR) modulators alter impulsive action in a nicotine self-administration Go/No-Go task in male and female rats. Rats acquired intravenous nicotine self-administration and were then trained in a Go/No-Go procedure in which active lever presses were reinforced during Go periods but not during No-Go periods. We then assessed the effects of varenicline (0.1-3 mg/kg), nicotine (0.1-0.6 mg/kg), and the nAChR antagonist mecamylamine (0.5-2 mg/kg) in the Go/No-Go procedure. Varenicline and nicotine pretreatment reduced active responding during both Go and No-Go periods, whereas mecamylamine selectively reduced responding during No-Go periods. Mecamylamine decreased the percentage of active responses during No-Go trials, indicating reduced bias toward the nicotine-associated lever. In contrast, nicotine and varenicline did not alter response allocation, suggesting that their effects reflected nonspecific reductions in responding rather than changes in impulsive action. No sex differences were observed. Substituting saline for nicotine during self-administration did not alter active responding during Go periods, but rats in the saline group had fewer active responses during No-Go periods than rats in the nicotine group. These results show that chronic nicotine self-administration increases impulsive action and that nAChR antagonism, but not agonism or partial agonism, reduces nicotine-related impulsive action. This work supports the utility of the Go/No-Go self-administration task for investigating nAChR-dependent mechanisms underlying nicotine-induced impulsivity.

BackgroundExternalizing liability is a strong risk factor for early substance initiation, but the neurobiological pathways linking polygenic risk to initiation remain incompletely characterized. MethodsUsing the ABCD Study, we implemented a four-stage framework linking an externalizing polygenic risk score (extPRS) to baseline multimodal neuroimaging-derived phenotypes (IDPs) and longitudinal substance initiation (alcohol [primary], nicotine, cannabis, and any substance). First, we screened extPRS-IDP associations using covariate-adjusted linear models (age, sex, ancestry principal components, site/scanner variables; modality-specific covariates where applicable) and controlled multiple testing using false discovery rate (FDR) procedures. Second, we estimated direct extPRS associations with time-to-initiation using Cox proportional hazards models. Third, we fit joint Cox models including extPRS and each discovery-significant IDP, retaining outcome-IDP associations after within-outcome FDR correction. Fourth, we conducted mediation analyses for prioritized outcome-IDP pairs using an extPRS [-&gt;] IDP mediator model and an initiation model including both extPRS and IDP, estimating indirect (ACME) and direct (ADE) effects via bootstrap with multiple-testing control. ResultsAmong 10,608 participants, higher extPRS was associated with earlier initiation across outcomes, with the largest effects observed for nicotine and cannabis and a modest but significant effect for alcohol. Stage 1 identified thousands of extPRS-associated IDPs that were highly concordant across robustness specifications. Stage 3 prioritized outcome-specific IDPs associated with initiation beyond extPRS, with the number of retained IDPs varying across sensitivity settings (site-clustered vs. HC3 standard errors; SES covariates on/off) but showing a replicated core set across models. In Stage 4, mediation analyses showed that indirect effects of extPRS through IDPs were small in magnitude (ACME {approx} 10-4) and accounted for less than 2% of the total effect, while direct effects (ADE {approx} 0.02-0.05) remained strong across outcomes. FDR-significant mediation signals were observed only for alcohol and any-substance initiation, whereas no mediation effects survived multiple testing correction for cannabis or nicotine. Across outcomes, direct genetic effects were substantially larger than mediated effects, indicating that genetic liability operates primarily through direct pathways rather than through baseline brain measures. ConclusionsExternalizing polygenic liability is broadly associated with substance initiation, with robust and consistent direct effects across substances. Although specific frontal structural and microstructural phenotypes show statistically significant mediation signals, their contribution is small, suggesting that baseline brain measures explain only a limited proportion of genetic risk. This framework provides a scalable approach to prioritize neurobiological pathways linking genetic liability to early substance initiation while highlighting the dominant role of direct genetic effects.