Adolescent drug exposure: A review of evidence for the development of persistent changes in brain function

Potential roles for microglia in drug addiction: Adolescent neurodevelopment and beyond

Adolescence is a sensitive period for development of addiction-relevant brain circuits, and it is also when people typically start experimenting with drugs. Unfortunately, such substance use may cause lasting impacts on the brain, and might increase vulnerability to later-life addictions. Microglia are the brain's immune cells, but their roles in shaping neural connectivity and synaptic plasticity, especially in developmental sensitive periods like adolescence, may also contribute to addiction-related phenomena. Here, we overview how drugs of abuse impact microglia, and propose that they may play poorly-understood, but important roles in addiction vulnerability and progression.

A Comprehensive Overview of Stress, Resilience, and Neuroplasticity Mechanisms

Stress is a core concept in the mental health field that expands upon the seminal definition of stress as an acute response to the disruption of homeostasis. Stress is a complex process that involves both environmental challenges and the triggering of internal responses and impacts physiological, psychological, and behavioral systems. The capacity of the human brain to cope with stress is particularly crucial in early life, when neurodevelopment is highly plastic. Early-life stress (ELS), defined as exposure to severe chronic stress during sensitive periods of development, has been shown to cause lasting changes in brain structure and function. However, not all individuals exposed to ELS develop pathological outcomes, suggesting the presence of resilience mechanisms: adaptive processes that allow an individual to cope with adverse situations while maintaining psychological and neurobiological health. The aim of this review was to synthesize recent advances in the understanding of the neuroplasticity mechanisms underlying resilience to ELS. We discussed the neurobiological pathways implicated in stress response and adaptation, including the roles of neurogenesis, synaptic plasticity, and neural circuit remodeling. By focusing on the interplay between stress-induced neuroplastic changes and resilience mechanisms, we aimed to provide insights into potential therapeutic targets for stress-related psychopathology.

School party culture as a driver of cocaine use among Norwegian adolescents: A cross-classified multilevel analysis

BACKGROUND

Adolescent substance use typically occurs within peer contexts and is influenced by characteristics of neighborhoods and the cultural environments of the schools adolescents attend. This study aimed to (i) examine variation in cocaine use among adolescents in Oslo, Norway, based on neighborhood of residence and high school affiliation; (ii) assess the significance of school-based party cultures; and (iii) identify individual-level correlates.

METHODS

The study used data from the Young in Oslo 2023 survey, which collected information from a population-based sample of senior high school students (n = 9741) residing in 95 neighborhoods and attending 25 schools. Participants completed e-questionnaires with information on cocaine use, neighborhood and school affiliation, school-based party cultures, sociodemographic variables, and potential correlates of cocaine use. The data were analyzed using cross-classified multilevel models (CCMM).

RESULTS

Of all adolescents, 9.3 % had used cocaine in the previous year. A CCMM including neighborhood and school showed an intraclass correlation coefficient (ICC) of 0.004 for neighborhood and 0.106 for school, indicating that 10.6 % of the variance in cocaine use was linked to school affiliation, while neighborhood variations were negligible. Including school party culture decreased the ICC for school to 0.055, suggesting this measure accounted for half the school-level variance. Further adjustments for individual-level correlates reduced the ICC to 0.028. The most significant individual factors were male gender, alcohol intoxication, and peers use of illicit drugs.

CONCLUSIONS

Certain youth milieus characterized by heavy-drinking boys and school-based party cultures increased cocaine use. Targeting these environments may be effective in prevention work.

Microglia-dependent peripheral neuropathic pain in adulthood following adolescent exposure to morphine in male rats

Persistent effects of adolescent morphine exposure on neurobiological processes and behaviors in adulthood have been partially identified. Hypersensitivity following adolescent exposure to morphine is a complex and multifaceted phenomenon whose underlying mechanisms remain largely unknown. This study aimed to investigate the involvement of microglia in neuropathic pain sensitivity following adolescent morphine exposure, focused on hippocampal genes expression and plasticity. To achieve this, adolescent male Wistar rats received morphine, along with minocycline, to inhibit microglial activity. The allodynia and hyperalgesia of adult rats were evaluated using von-Frey filaments and the Hargreaves plantar test in both baseline and neuropathic pain conditions. Hippocampal genes expression was analyzed following the behavioral tests. The plasticity of the Schaffer-CA1 hippocampal synapses was also assessed using field potential recording following neuropathy. Results showed that adolescent morphine exposure exacerbated the allodynia and hyperalgesia in both baseline and neuropathic pain states in adult rats, which was significantly reduced by the co-administration of minocycline during adolescence. Neuropathy in adult rats was found to increase hippocampal expression of inflammatory mediators, but adolescent morphine prevented this effect. Additionally, we observed a reduction in the baseline synaptic transmission and long-term potentiation (LTP) at the Schaffer-CA1 hippocampal synapses after neuropathy in adult rats following adolescent exposure to morphine. The reduction of synaptic activity was not altered by the co-administration of minocycline with morphine during adolescence. It is concluded that microglia play an important role in mediating hypersensitivity induced by adolescent morphine exposure, although hippocampal microglia may not be directly involved in this process.

Adult and adolescent antipsychotic exposure increases delay discounting and diminishes behavioral flexibility in male C57BL/6 mice

Second-generation antipsychotics are frequently prescribed to adolescents, but the long-term consequences of their use remain understudied. These medications work via monoamine neurotransmitter systems, especially dopamine and serotonin, which undergo considerable development and pruning during adolescence. Dopamine and serotonin are linked to a wide host of behaviors, including impulsive choice and behavioral plasticity. In a murine model of adolescent antipsychotic use, male C57BL/6 mice were exposed to either 2.5 mg/kg/day risperidone or 5 mg/kg/day olanzapine via drinking water from postnatal days 22-60. To determine whether the adolescent period was uniquely sensitive to antipsychotic exposure, long-term effects on behavior were compared to an equivalently exposed group of adults where mice were exposed to 2.5 mg/kg risperidone from postnatal days 101-138. Motor activity and body weight in adolescent animals were assessed. Thirty days after exposure terminated animal's behavioral flexibility and impulsive choice were assessed using spatial discrimination reversal and delay discounting. Antipsychotic exposure produced a modest change in behavior flexibility during the second reversal. There was a robust and reproducible difference in impulsive choice: exposed animals devalued the delayed alternative reward substantially more than controls. This effect was observed both following adolescent and adult exposure, indicating that an irreversible change in impulsive choice occurs regardless of the age of exposure.

Understanding alcohol use and alcohol use disorders from a developmental psychopathology perspective: Research advances, challenges, and future directions

As part of the special issue of Development and Psychopathology honoring the remarkable contributions of Dr Dante Cicchetti, the current paper attempts to describe the recent contributions that a developmental psychopathology perspective has made in understanding the development of alcohol use and alcohol-related problems over the lifespan. The paper also identifies some of the future challenges and research directions. Because the scope of this task far exceeds the confines of a journal length article this paper does not attempt a comprehensive review. Rather, it builds on an earlier review and commentary that was published in Development and Psychopathology in 2013, with a similar goal.)Building on that work and updating its conclusions and suggestions for future directions, the current paper emphasizes findings from the research areas that were identified for further study in 2013 and the findings that have been published since that time.

Hair Cortisol Concentrations in the Prediction of Early Substance Use Engagement in Youth

OBJECTIVE

Understanding factors associated with early onset of substance use is critical as using alcohol or drugs at a young age is a strong predictor of later substance dependency. Experiencing stressful life events is associated with increased risk for early substance use in youth. Hair cortisol concentration (HCC) is considered a biomarker of psychological stress experienced over longer periods of time. We examined whether HCC could predict early substance use engagement in youth followed over 5 years.

METHODS

Participants were 395 young adolescents (50% female, age range 10-15 years, Mage = 12.3, SD = 1.1 at baseline). Demographic data, socioeconomic factors, and substance use habits were collected at four waves between 2015 and 2021. HCC was assayed from hair collected at a home visit between Wave 1 and Wave 2. Analytic models tested a) HCC in relation to latent class membership of substance use and b) whether HCC moderated the relation between self-reports of stress and substance use.

RESULTS

HCC did not add to the prediction of early substance use engagement in any of the models, while self-reports of stressful life events and everyday discrimination predicted early substance use engagement in the models comparing 'Early' vs 'Late/No' substance use class membership.

CONCLUSION

We found no evidence of HCC to be associated with early substance use engagement in youth. Nevertheless, our results do confirm that self-reports of stressful everyday life experiences predict earlier substance use engagement, underscoring the role of psychosocial stressors as significant predictors of substance use engagement in youth.

Acupuncture in the treatment of cocaine addiction: how does it work?

Cocaine is a frequently abused and highly addictive drug that damages brain health and imposes substantial social and economic costs. Acupuncture has been used in the treatment of cocaine addiction and has been shown to improve abnormal mental and motor states. This article mainly focuses on the neurobiological mechanisms involving the central nervous system (CNS) and peripheral nervous system (PNS) that underlie the effects of acupuncture in the treatment of cocaine addiction. The central dopamine system is a key player in acupuncture treatment of cocaine addiction; the ventral tegmental area (VTA)-nucleus accumbens (NAc) signaling pathway, which has a modulatory influence on behavior and psychology after chronic use of cocaine, is a significant target of acupuncture action. Moreover, acupuncture alleviates cocaine-induced seizures or acute psychomotor responses through the paraventricular thalamus and the lateral habenula (LHb)-rostromedial tegmental (RMTg) nucleus circuits. The data suggest that acupuncture can impact various cocaine-induced issues via stimulation of diverse brain areas; nevertheless, the interconnection of these brain regions and the PNS mechanisms involved remain unknown. In this review, we also discuss the effects of specific acupuncture protocols on cocaine addiction and note that variations in needling modalities, current intensities and traditional acupuncture point locations have led to different experimental results. Therefore, standardized acupuncture protocols (with respect to stimulation methods, point locations and number of sessions) may become particularly important in future studies.

Development of the modified Highly Processed Food Withdrawal Scale (mProWS)

The Highly Processed Food Withdrawal Scale (ProWS) is a 29-item measure that operationalizes physical and psychological indicators of withdrawal symptoms associated with cutting down on the consumption of ultra-processed foods. The current study developed a briefer 7-item version of the ProWS (modified ProWS; mProWS) using the participant sample from the ProWS validation paper (n = 231). Then, in an independent sample recruited from Amazon Mechanical Turk, 244 participants (55.3% females) completed the mProWS, the ProWS, and measures of eating-related constructs in order to evaluate the psychometric properties of the mProWS, relative to the ProWS. The mProWS and the ProWS performed similarly on indexes of reliability, convergent validity with addictive-like eating behavior (e.g., Yale Food Addiction Scale 2.0 symptom count), discriminant validity with distinct measures (e.g., cognitive desire to restrict food consumption), and incremental validity evidenced by associations with weight cycling above and beyond body mass index (BMI) and YFAS 2.0 symptoms. The mProWS may be an appropriate choice for studies with higher participant burden (e.g., ecological momentary assessment) to assess withdrawal symptoms in real-time when they occur in response to cutting down on ultra-processed foods.

The acute effects of cannabis, with and without cannabidiol, on attentional bias to cannabis related cues: a randomised, double-blind, placebo-controlled, cross-over study

RATIONALE

Attentional bias to drug-related stimuli is hypothesised to contribute towards addiction. However, the acute effects of Δ9-tetrahydrocannabinol (THC) on attentional bias to cannabis cues, the differential response in adults and adolescents, and the moderating effect of cannabidiol (CBD) are unknown.

OBJECTIVES

Our study investigated (1) the acute effects of vaporised cannabis on attentional bias to cannabis-related images in adults and adolescents and (2) the moderating influences of age and CBD.

METHODS

We conducted a randomised, double-blind, placebo-controlled, cross-over study where three weight-adjusted vaporised cannabis preparations: 'THC' (8 mg THC for a 75-kg person), 'THC + CBD' (8 mg THC and 24 mg CBD for a 75-kg person) and PLA (matched placebo). Cannabis was administered on 3 separate days to 48 participants, who used cannabis 0.5-3 days/week: 24 adolescents (12 females, aged 16-17) and 24 adults (12 females, aged 26-29). Participants completed a visual probe task with cannabis cues. Our primary outcome was attentional bias to cannabis stimuli, measured using the differential reaction time to a cannabis vs. neutral probe, on 200-ms trials.

RESULTS

In contrast to hypotheses, attention was directed away from cannabis cues on placebo, and there was a main effect of the drug (F(2,92) = 3.865, p = 0.024, η2p = 0.077), indicating THC administration eliminated this bias. There was no significant impact of CBD nor an age-by-drug interaction.

CONCLUSIONS

Acute THC intoxication eliminated attentional bias away from cannabis cues. There was no evidence of differential response in adolescents compared to adults and no evidence that a moderate vaporised dose of CBD altered the impact of cannabis on attentional bias.

TRIAL REGISTRATION

This study was listed with the US National Library of Medicine and registered on ClinicalTrials.gov, URL: Do Adolescents and Adults Differ in Their Acute Response to Cannabis?-Full Text View-ClinicalTrials.gov, registration number: NCT04851392.

Oral administration of coenzyme Q10 ameliorates memory impairment induced by nicotine-ethanol abstinence through restoration of biochemical changes in male rat hippocampal tissues

Substance abuse among adolescents has become a growing issue throughout the world. The significance of research on this life period is based on the occurrence of neurobiological changes in adolescent brain which makes the individual more susceptible for risk-taking and impulsive behaviors. Alcohol and nicotine are among the most available drugs of abuse in adolescents. Prolonged consumption of nicotine and alcohol leads to drug dependence and withdrawal which induce various dysfunctions such as memory loss. Coenzyme Q10 (CoQ10) is known to improve learning and memory deficits induced by various pathological conditions such as Diabetes mellitus and Alzheimer's disease. In the present study we investigated whether CoQ10 treatment ameliorates memory loss following a nicotine-ethanol abstinence. Morris water maze and novel object recognition tests were done in male Wistar rats undergone nicotine-ethanol abstinence and the effect of CoQ10 was assessed on at behavioral and biochemical levels. Results indicated that nicotine-ethanol abstinence induces memory dysfunction which is associated with increased oxidative and inflammatory response, reduced cholinergic and neurotrophic function plus elevated Amyloid-B levels in hippocampi. CoQ10 treatment prevented memory deficits and biochemical alterations. Interestingly, this ameliorative effect of CoQ10 was found to be dose-dependent in most experiments and almost equipotential to that of bupropion and naloxone co-administration. CoQ10 treatment could effectively improve memory defects induced by nicotine-ethanol consumption through attenuation of oxidative damage, inflammation, amyloid-B level and enhancement of cholinergic and neurotrophic drive. Further studies are required to assess the unknown side effects and high dose tolerability of the drug in human subjects.

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.

Cognitive training interventions for substance use disorders: what they really offer?

Cognitive training (CT) has emerged as a potential therapeutic approach for substance use disorders (SUD), aiming to restore cognitive impairments and potentially improve treatment outcomes. However, despite promising findings, the effectiveness of CT in real-life applications and its impact on SUD symptoms has remained unclear. This perspective article critically examines the existing evidence on CT for SUD and explores the challenges and gaps in implementing CT interventions. It emphasizes the need for clarity in expectations and decision-making from a public health standpoint, advocating for comprehensive studies that consider a broader range of SUD consequences and utilize measures that reflect patients' actual experiences.

Neuron enriched extracellular vesicles' MicroRNA expression profiles as a marker of early life alcohol consumption

Alcohol consumption may impact and shape brain development through perturbed biological pathways and impaired molecular functions. We investigated the relationship between alcohol consumption rates and neuron-enriched extracellular vesicles' (EVs') microRNA (miRNA) expression to better understand the impact of alcohol use on early life brain biology. Neuron-enriched EVs' miRNA expression was measured from plasma samples collected from young people using a commercially available microarray platform while alcohol consumption was measured using the Alcohol Use Disorders Identification Test. Linear regression and network analyses were used to identify significantly differentially expressed miRNAs and to characterize the implicated biological pathways, respectively. Compared to alcohol naïve controls, young people reporting high alcohol consumption exhibited significantly higher expression of three neuron-enriched EVs' miRNAs including miR-30a-5p, miR-194-5p, and miR-339-3p, although only miR-30a-5p and miR-194-5p survived multiple test correction. The miRNA-miRNA interaction network inferred by a network inference algorithm did not detect any differentially expressed miRNAs with a high cutoff on edge scores. However, when the cutoff of the algorithm was reduced, five miRNAs were identified as interacting with miR-194-5p and miR-30a-5p. These seven miRNAs were associated with 25 biological functions; miR-194-5p was the most highly connected node and was highly correlated with the other miRNAs in this cluster. Our observed association between neuron-enriched EVs' miRNAs and alcohol consumption concurs with results from experimental animal models of alcohol use and suggests that high rates of alcohol consumption during the adolescent/young adult years may impact brain functioning and development by modulating miRNA expression.

Fine-Regional Role of the Claustrum in Anxiety and Higher Sensitivity to Cocaine in Adolescent Cocaine-Exposed Male Mice during Adulthood

Adolescent cocaine exposure (ACE) induces anxiety and higher sensitivity to substances abuse during adulthood. Here, we show that the claustrum is crucial for controlling these psychiatric problems in male mice. In anxiety-like behavioral tests, the CaMKII-positive neurons in the median portion of the claustrum (MClaustrum) were triggered, and local suppression of these neurons reduced the anxiety-like behavior in ACE mice during adulthood. In contrast, the CaMKII-positive neurons in the anterior portion of the claustrum (AClaustrum) were more activated in response to subthreshold dose of cocaine induced conditioned place preference (CPP), and local suppression of these neurons blocked the acquisition of cocaine CPP in ACE mice during adulthood. Our findings for the first time identified the fine-regional role of the claustrum in regulating the anxiety and susceptibility to cocaine in ACE mice during adulthood, extending our understanding of the claustrum in substance use disorder.

Adolescent morphine exposure changes the endogenous vlPAG opioid response to inflammatory pain in rats

Adolescence is one of the most critical periods for brain development, and exposure to morphine during this period can have long-life effects on pain-related behaviors. The opioid system in the periaqueductal gray (PAG) is highly vulnerable to drug exposure. However, the impact of adolescent morphine exposure (AME) on the endogenous opioid system in the PAG is currently unknown. This study aims to investigate the long-lasting effects of AME on the endogenous opioid system and its involvement in altering nociceptive behaviors. Adolescent rats were given escalating doses of morphine (2.5-25 mg/kg, subcutaneous) or an equal volume of saline twice daily for 10 consecutive days (PND 31-40). After a 30-day washout period, adult rats underwent formalin tests following microinjection of morphine, naloxone, or saline into the ventrolateral PAG (vlPAG) region. The results indicated that morphine microinjection into the vlPAG of the adolescent morphine-treated group significantly reduced the nociceptive score. However, the analgesic response to morphine in this group was significantly lower compared to the saline-treated group during adolescence. Additionally, the nociceptive score significantly increased following naloxone but not saline microinjection into the vlPAG of the saline-treated group during adolescence, rather than the morphine-treated one. These findings indicate that AME has long-lasting effects on the endogenous opioid system in the vlPAG, which can consequently alter behaviors related to inflammatory pain in adulthood.

Substance Use and Addiction

Efforts to reveal the molecular, cellular, and circuit mechanisms of addiction have largely focused on neurons. Yet accumulating data regarding the ability of glial cells to impact synaptic function, circuit activity, and behavior demands that we explore how these nonneuronal cells contribute to substance use disorders and addiction. Important work has shown that glial cells, including microglia, exhibit changes in phenotype following exposure to drugs of abuse and that modification of glial responses can impact behaviors related to drug seeking and drug taking. While these are critical first steps to understanding how microglia can impact addiction, there are still substantial gaps in knowledge that need to be addressed. This chapter reviews some of the key studies that have shown how microglia are affected by and can contribute to addiction. It also discusses areas where more knowledge is urgently needed to reveal new therapeutic and preventative approaches.

Age-dependent memory impairment induced by co-exposure to nicotine and a synthetic cannabinoid in mice

Co-use of marijuana and tobacco products is the second most common drug combination among adolescents. Nicotine (NIC) and cannabinoid use during adolescence induce similar detrimental changes, raising the hypothesis that simultaneous exposure could result in even more severe outcomes. Thus, we investigated whether the co-exposure to NIC and the synthetic cannabinoid WIN 55,212-2 (WIN) in adolescent mice causes behavioral outcomes different from those observed after exposure to a single drug. Male Swiss mice were exposed twice daily to NIC, WIN, or NIC + WIN during adolescence (PND28-47) or adulthood (PND70-89). Drug combination led to a greater reduction in weight gain in adolescent mice, while NIC-induced weight loss was observed in adults. During administration, NIC provoked hypothermia, and WIN produced hyperlocomotion in adolescent and adult mice. Animals exposed to NIC + WIN presented a profile of changes similar to those exposed to NIC. After drug exposure, changes in locomotion, thigmotaxis, social preference, prepulse inhibition, and working and recognition memory were evaluated. Adolescent but not adult mice exposed to NIC showed withdrawal-related hyperlocomotion unaffected by WIN co-administration. An age-specific impairment in object recognition memory was induced only by drug co-exposure during adolescence, which resolved spontaneously before reaching early adulthood. A transient decrease in hippocampal α7 nAChR subunit and CB1 receptor mRNA levels was induced by NIC exposure, which may be involved but is not enough to explain the memory impairment. Our work confirms the potential of NIC and cannabinoids association to aggravate some of the individual drug effects during critical neurodevelopmental periods.

Omega-3 fatty acids prevent nicotine withdrawal-induced impairment of learning and memory via affecting oxidative status, inflammatory response, cholinergic activity, BDNF and amyloid-B in rat hippocampal tissues

In the present study, the main objective was to reveal whether treatment by Omega-3 fatty acids could prevent the adverse effects of adolescent nicotine withdrawal on spatial and avoidance memory in male rats. For this purpose, Morris water maze and passive avoidance tests were performed on male Wistar rats and the hippocampal levels of oxidative stress markers, inflammatory indices, brain-derived neurotrophic factor, nitrite, amyloid-B and acetylcholinesterase (AChE) were measured. Moreover, density of dark neurons were assessed in CA1 and CA3 regions. Results showed that adolescent nicotine exposure followed by a period of drug cessation exacerbates the behavioral indices of learning and memory through affecting a variety of biochemical markers within the hippocampal tissues. These changes lead to elevation of oxidative and inflammatory markers, reduction of neurotrophic capacity and increased AChE activity in hippocampal tissues. In addition, it was observed that co-administration of nicotine with Omega-3 fatty acids significantly prevents nicotine withdrawal-induced adverse effects through restoration of the mentioned biochemical disturbances. Therefore, we suggest administration of Omega-3 fatty acids as a safe, inexpensive and effective therapeutic strategy for prevention of memory dysfunctions associated with nicotine abstinence during adolescence.

Consequences of adolescent drug use

Substance use in adolescence is a known risk factor for the development of neuropsychiatric and substance use disorders in adulthood. This is in part due to the fact that critical aspects of brain development occur during adolescence, which can be altered by drug use. Despite concerted efforts to educate youth about the potential negative consequences of substance use, initiation remains common amongst adolescents world-wide. Additionally, though there has been substantial research on the topic, many questions remain about the predictors and the consequences of adolescent drug use. In the following review, we will highlight some of the most recent literature on the neurobiological and behavioral effects of adolescent drug use in rodents, non-human primates, and humans, with a specific focus on alcohol, cannabis, nicotine, and the interactions between these substances. Overall, consumption of these substances during adolescence can produce long-lasting changes across a variety of structures and networks which can have enduring effects on behavior, emotion, and cognition.

Understanding the complexity, patterns, and correlates of alcohol and other substance use among young people seeking help for mental ill-health

PURPOSE

Use of alcohol and other substances is a multifaceted issue impacting young people across multiple life domains. This paper aims to elucidate patterns of substance use and associated demographic and clinical factors among young people seeking treatment for their mental health.

METHODS

Young people (12-25 years old) were recruited from five youth-specific primary mental health ("headspace") services in Australia. Self-reported substance use and harms in the past 3 months were measured using WHO-ASSIST. Network analyses were conducted to evaluate interrelationships between use and harms associated with different substances. Subgroups were then identified based on whether participants reported using high centrality substances, and associated demographic and clinical factors were assessed with multinomial logistic regression.

RESULTS

1107 youth participated. 70% reported use of at least one substance in the past 3 months, with around 30% of those reporting related health, social, legal or financial problems. Network analysis highlighted substantial interconnections between use and harm indicators for all substances, with amphetamine-type stimulants (ATS) and cannabis being high central substances. Higher levels of substance use and harms were reported in subgroups with ATS or cannabis use and different risk factors were associated with these subgroups.

CONCLUSIONS

Findings highlight the importance of screening for substance use in youth primary mental healthcare settings, offering a key opportunity for early intervention. Clinicians should be aware of the inner connections of use and harms of different drugs and the role of cannabis and amphetamine use as a marker for more substance use profiles.

Associations between alcohol intake and hospital contacts due to alcohol and unintentional injuries in 71,025 Danish adolescents - a prospective cohort study

Background

Alcohol is a leading risk factor to adolescent health. However, it is unclear how associations between alcohol intake and injuries are shaped. We investigated the dose-response relationship between alcohol intake and risk of hospital contacts due to alcohol and unintentional injuries in adolescents.

Methods

We conducted a prospective cohort study including 71,025 Danish students aged 15-24 years, followed up for five years from 2014 to 2019. The main outcome measures were hospital contacts due to alcohol and unintentional injuries (all injuries and head injuries), obtained from hospital registers.

Findings

Approximately 90% of males and females reported drinking alcohol, and the median intake among those was 11 drinks/week in males and 8 drinks/week in females. During five years of follow-up, 1.3% had an alcohol-attributable hospital contact, the majority of which were due to acute intoxication (70%). Alcohol-attributable hospital contacts were equally frequent in males and females and between age groups (15-17-year-olds vs 18-24-year-olds). Compared with never drinking, the adjusted incidence rate ratios for weekly intake of <7, 7-13, 14-20, 21-27, and >27 drinks/week were 1.70 (95% confidence interval 1.23-2.34), 1.77 (1.27-2.46), 1.91 (1.35-2.70), 2.34 (1.59-3.46), and 3.25 (2.27-4.64) for having an alcohol-attributable hospital contact within five years of follow-up. Restricting follow-up to one year more than doubled risk estimates. During the five years of follow-up, 27% incurred an unintentional injury. The most frequent types of injury were to the wrist or hand (27.6%), ankle or foot (25.2%), or head (12.4%). Injuries were more frequent among males (first-time incidence rate 110 per 1000 person-years) compared to females (82 per 1000 person-years), with no differences between age groups. Compared with never drinking, the adjusted incidence rate ratios for weekly intake of <7, 7-13, 14-20, 21-27, and >27 drinks were 1.09 (1.03-1.15), 1.14 (1.07-1.20), 1.25 (1.17-1.33), 1.38 (1.28-1.49), and 1.58 (1.47-1.69) for having a hospital contact for any type of unintentional injury within five years of follow-up. Results for the one-year follow-up period were comparable. Separate analysis for head injuries showed similar results as the analysis on all injuries. Results were generally similar in males and females.

Interpretation

Adolescents' drinking is associated with a higher risk of acute harm in terms of hospital contacts due to alcohol and unintentional injuries in a dose-response relationship. Thus, increased risk was apparent in those with low alcohol intake, suggesting a need for awareness of and initiatives to prevent youth drinking. Furthermore, initiatives should include a strengthened focus on people younger than 18 years.

Funding

This study was funded by the Tryg Foundation (ID: 153539) and The Helse Foundation (21-B-0359).

Association between vmPFC gray matter volume and smoking initiation in adolescents

Smoking of cigarettes among young adolescents is a pressing public health issue. However, the neural mechanisms underlying smoking initiation and sustenance during adolescence, especially the potential causal interactions between altered brain development and smoking behaviour, remain elusive. Here, using large longitudinal adolescence imaging genetic cohorts, we identify associations between left ventromedial prefrontal cortex (vmPFC) gray matter volume (GMV) and subsequent self-reported smoking initiation, and between right vmPFC GMV and the maintenance of smoking behaviour. Rule-breaking behaviour mediates the association between smaller left vmPFC GMV and smoking behaviour based on longitudinal cross-lagged analysis and Mendelian randomisation. In contrast, smoking behaviour associated longitudinal covariation of right vmPFC GMV and sensation seeking (especially hedonic experience) highlights a potential reward-based mechanism for sustaining addictive behaviour. Taken together, our findings reveal vmPFC GMV as a possible biomarker for the early stages of nicotine addiction, with implications for its prevention and treatment.

Quality of life of services users in psychotropic drug treatment and rehabilitation services: a qualitative study from service user and provider perspectives

Quality of life (QoL) is a widely recognized and valuable social outcome measure in drug treatment and rehabilitation services, but the discrepancies in QoL perceptions between service users and providers remain under-explored. In this study, semi-structured interviews were conducted with service users (n = 22) and providers (n = 29) to capture their perceptions of QoL and explore the similarities and discrepancies between their views. A thematic analysis and contrast exploration revealed a shared understanding of QoL that extends beyond health to six dimensions and prioritizes empowerment and connection. However, divergent views emerged regarding the priorities of material conditions, emotional well-being, and physical health. Findings underscore the importance of using shared decision-making as a strategy to effectively address these discrepancies and promote a more patient-centered approach in treatment and rehabilitation services.

Neuron Enriched Exosomal MicroRNA Expression Profiles as a Marker of Early Life Alcohol Consumption

Background

Alcohol consumption may impact and shape brain development through perturbed biological pathways and impaired molecular functions. We investigated the relationship between alcohol consumption rates and neuron-enriched exosomal microRNA (miRNA) expression to better understand the impact of alcohol use on early life brain biology.

Methods

Neuron-enriched exosomal miRNA expression was measured from plasma samples collected from young people using a commercially available microarray platform while alcohol consumption was measured using the Alcohol Use Disorders Identification Test. Linear regression and network analyses were used to identify significantly differentially expressed miRNAs and to characterize the implicated biological pathways, respectively.

Results

Compared to alcohol naïve controls, young people reporting high alcohol consumption exhibited significantly higher expression of four neuron-enriched exosomal miRNAs including miR-30a-5p, miR-194-5p, and miR-339-3p, although only miR-30a-5p and miR-194-5p survived multiple test correction. The miRNA-miRNA interaction network inferred by a network inference algorithm did not detect any differentially expressed miRNAs with a high cutoff on edge scores. However, when the cutoff of the algorithm was reduced, five miRNAs were identified as interacting with miR-194-5p and miR-30a-5p. These seven miRNAs were associated with 25 biological functions; miR-194-5p was the most highly connected node and was highly correlated with the other miRNAs in this cluster.

Conclusions

Our observed association between neuron-enriched exosomal miRNAs and alcohol consumption concurs with results from experimental animal models of alcohol use and suggests that high rates of alcohol consumption during the adolescent/young adult years may impact brain functioning and development by modulating miRNA expression.

Early life adversity: Epigenetic regulation underlying drug addiction susceptibility

Drug addiction is a leading cause of disability worldwide, with more than 70,000 Americans dying from drug overdose in 2019 alone. While only a small percentage of chronic drug users escalate to drug addiction, little is understood on the precise mechanisms of this susceptibility. Early life adversity is causally relevant to adult psychiatric disease and may contribute to the risk of addiction. Here we review recent pre-clinical evidence showing that early life exposure to stress and/or drugs regulates changes in behavior, gene expression, and the epigenome that persist into adulthood. We summarize the major findings and gaps in the preclinical literature, highlighting studies that demonstrate the often profound differences between female and male subjects.

Intergenerational consequences of adolescent morphine exposure on learning and memory

Drug addiction is a worldwide social and medical disorder. More than 50 percent of drug abusers start their substance abuse in adolescence between the ages of 15-19. Adolescence is a sensitive and crucial period for the development and maturity of the brain. Chronic exposure to morphine, particularly during this period, lead to long-lasting effects, including effects that extend to the next generation. The current study examined the intergenerational effects of paternal morphine exposure during adolescence on learning and memory. In this study, male Wistar rats were exposed to increasing doses of morphine (5-25 mg/kg, s.c.) or saline for 10 days at postnatal days (PND) 30-39 during adolescence. Following a 20-day drug-free period, the treated male rats were mated with naïve females. Adult male offspring (PND 60-80) were tested for working memory, novel object recognition memory, spatial memory, and passive avoidance memory using the Y-Maze, novel object recognition, Morris water maze, and shuttle box tests, respectively. The spontaneous alternation (as measured in the Y-Maze test) was significantly less in the morphine-sired group compared to the saline-sired one. The offspring showed significantly less discrimination index in the novel object recognition test when compared to the control group. Morphine-sired offspring tended to spend significantly more time in the target quadrant and less escape latency in the Morris water maze on probe day when compared to the saline-sired ones. The offspring showed significantly less step-through latency to enter the dark compartment compared to the control group when measured in the shuttle box test. Paternal exposure to morphine during adolescence impaired working, novel object recognition, and passive avoidance memory in male offspring. Spatial memory changed in the morphine-sired group compared to the saline-sired one.

Morphine exposure during adolescence induces enduring social changes dependent on adolescent stage of exposure, sex, and social test

Drug exposure during adolescence, when the 'reward' circuitry of the brain is developing, can permanently impact reward-related behavior. Epidemiological studies show that opioid treatment during adolescence, such as pain management for a dental procedure or surgery, increases the incidence of psychiatric illness including substance use disorders. Moreover, the opioid epidemic currently in the United States is affecting younger individuals raising the impetus to understand the pathogenesis of the negative effects of opioids. One reward-related behavior that develops during adolescence is social behavior. We previously demonstrated that social development occurs in rats during sex-specific adolescent periods: early to mid-adolescence in males (postnatal day (P)30-40) and pre-early adolescence in females (P20-30). We thus hypothesized that morphine exposure during the female critical period would result in adult sociability deficits in females, but not males, and morphine administered during the male critical period would result in adult sociability deficits in males, but not females. We found that morphine exposure during the female critical period primarily resulted in deficits in sociability in females, while morphine exposure during the male critical period primarily resulted in deficits in sociability primarily in males. However, depending on the test performed and the social parameter measured, social alterations could be found in both sexes that received morphine exposure at either adolescent stage. These data indicate that when drug exposure occurs during adolescence, and how the endpoint data are measured, will play a large role in determining the effects of drug exposures on social development.

Substance Use Experiences Among Bisexual, Pansexual, and Queer (Bi+) Male Youth: A Qualitative Study of Motivations, Consequences, and Decision Making

Sexual minority youth are at increased risk of substance use compared to their heterosexual peers, and bisexual youth appear to be at greatest risk. However, little is known about their motivations for and against using substances, how they make decisions, and what consequences they experience. We used qualitative data from a study of 54 cisgender and transgender male youth (ages 14-17 years) who reported attractions to more than one gender or regardless of gender (i.e., bisexual, pansexual, or queer; collectively referred to as bi+) to explore these aspects of substance use. Participants completed a survey and an interview, and interviews were thematically analyzed. Qualitative analyses revealed that participants described diverse motivations for using substances (e.g., to cope with stress, to experiment, to have fun) and for not using them (e.g., concern about consequences, not having access). The most common sources of stress were mental health problems, school, and family. They did not describe sexual orientation-related stress as a motivation for their use, but they acknowledged that it could influence others' use. Participants also described thinking about when, where, and with whom they were going to use prior to doing so (e.g., only using in safe places and with people who they trusted). Finally, they described a range of consequences they experienced (e.g., getting sick, getting in trouble), and a subset of transgender participants described experiencing dependence symptoms. These findings suggest that substance use prevention and harm reduction interventions for bi+ male youth should address diverse motivations for use, including general stressors, which are often overlooked compared to minority-specific stressors. Further, interventions should approach youth as capable of making decisions. Findings also highlight the particular need to address substance use among transgender youth.

Recommendations for Reducing the Risk of Cannabis Use-Related Adverse Psychosis Outcomes: A Public Mental Health-Oriented Evidence Review

Objective: Cannabis use is increasingly normalized; psychosis is a major adverse health outcome. We reviewed evidence on cannabis use-related risk factors for psychosis outcomes at different stages toward recommendations for risk reduction by individuals involved in cannabis use. Methods: We searched primary databases for pertinent literature/data 2016 onward, principally relying on reviews and high-quality studies which were narratively summarized and quality-graded; recommendations were developed by international expert consensus. Results: Genetic risks, and mental health/substance use problem histories elevate the risks for cannabis-related psychosis. Early age-of-use-onset, frequency-of-use, product composition (i.e., THC potency), use mode and other substance co-use all influence psychosis risks; the protective effects of CBD are uncertain. Continuous cannabis use may adversely affect psychosis-related treatment and medication effects. Risk factor combinations further amplify the odds of adverse psychosis outcomes. Conclusions: Reductions in the identified cannabis-related risks factors-short of abstinence-may decrease risks of related adverse psychosis outcomes, and thereby protect cannabis users' health.

Sexual minority status, illicit drug use, and depressive symptoms

Youth who are lesbian, gay, bisexual, and who identify with other sexual orientations (LGB+) are at higher risk for illicit drug use and have higher rates of mental illness. The current study examined the prevalence of illicit drug use among LGB+ persons and assessed the moderating effect of mental illness. Cross-sectional data from the 2015, 2017, and 2019 Youth Risk Behavioral Surveillance System were aggregated. The outcome was any reported use of cocaine, inhalants, heroin, methamphetamines, ecstasy, or hallucinogens. The primary exposure was self-reported sexual orientation category (i.e., heterosexual, gay/lesbian, bisexual, not sure). Self-reported depressive symptoms were tested as a moderator. Logistic regression models assessed main and interactive effects. Gay or lesbian students [AOR=1.87 95%CI: 1.45,2.43], bisexual students [AOR=2.07 95%CI: 1.77,2.42], and those unsure of their sexual orientation [AOR=1.99 95%CI: 1.65,2.39] had increased odds of illicit drug use. Odds were higher among LGB+ youth who did not have depressive symptoms (p<0.001). Odds of illicit substance use was significantly greater in youth identifying as gay and lesbian, bisexual, and students who were not sure about their sexual orientation and among LGB+ youth without depressive symptoms. Targeted, but non-stigmatizing, prevention programs are needed.

Vitamin B12 administration prevents ethanol-induced learning and memory impairment through re-establishment of the brain oxidant/antioxidant balance, enhancement of BDNF and suppression of GFAP

There are growing evidence indicating that the adolescent brain is persistently affected by the use of psychostimulant agents. In this regard, alcohol drinking has become rather common among the adolescents in many societies during the last decade. It is currently well known that long-term ethanol exposure deteriorates various cognitive functions such as learning and memory. Mechanistically, these adverse effects have been shown to be mediated by oxidative damage to central nervous system. On the other hand, Vit-B12 is known to improve cognitive performance by suppression of oxidative parameters. Thus, in the present study we aimed to test whether treatment by Vit-B12 could prevent ethanol-induced complications in mice using behavioral and biochemical methods. Different groups of male Syrian mice received ethanol, ethanol+Vit-B12, Vit-B12 alone, or saline during adolescence and then learning and memory functions were assessed by Morris water maze (MWM) and Passive Avoidance (PA) tests. Finally, mice were sacrificed for measurement of biochemical factors. Results indicated that, adolescent ethanol intake impairs learning and memory function through exacerbation of oxidative stress and Vit-B12 treatment improves these complications by re-establishment of oxidant/anti-oxidant balance in CNS. Moreover, we found that Vit-B12 prevents ethanol-induced reduction of BDNF and enhancement of GFAP and acetylcholinesterase (AChE) activity. In conclusion, it seems that Vit-B12 supplementation could be used as an effective therapeutic strategy to prevent learning and memory defects induced by chronic alcohol intake during adolescence.

Alcohol and cannabinoid binges and daily exposure to nicotine in adolescent/young adult rats induce sex-dependent long-term appetitive instrumental learning impairment

Adolescence is a critical developmental period, concerning anatomical, neurochemical and behavioral changes. Moreover, adolescents are more sensitive to the long-term deleterious effects of drug abuse. Binge-like consumption of alcohol and marijuana, along with tobacco smoking, is a dangerous pattern often observed in adolescents during weekends. Nevertheless, the long-term effect of their adolescent co-exposure has not been yet experimentally investigated. Long-Evans adolescent male (n = 20) and female (n = 20) rats from postnatal day 30 (P30) until P60 were daily treated with nicotine (0.3 mg/kg, i.p.), and, on two consecutive 'binging days' per week (for a total of eight times), received an intragastric ethanol solution (3 g/kg) and an intraperitoneal (i.p.) dose of cannabinoid 1/2 receptor agonist WIN55,212-2 (1.2 mg/kg). These rats were tested after treatment discontinuation at > P90 for associative food-rewarded operant learning in the two-lever conditioning chambers for six consecutive days on a fixed ratio 1 (FR1) schedule followed by another six days of daily FR2 schedule testing, after 42 days rest. We found the main effects of sex x treatment interactions in FR1 but not in FR2 experiments. Treated females show attenuated operant responses for food pellets during all FR1 and the FR2 schedule, whilst the treated males show an impairment in FR2 but not in the FR1 schedule. Moreover, the treated females' percentage of learners was significantly lower than female controls in FR1 while treated males were lower than controls in FR2. Our findings suggest that intermittent adolescent abuse of common drugs, such as alcohol and marijuana, and chronic tobacco exposure can cause significant long-term effects on motivation for natural reinforcers later in adulthood in both sexes. Females appear to be sensitive earlier to the deleterious effects of adolescent polydrug abuse, with both sexes having an increased likelihood of developing lifelong brain alterations.

Adolescent morphine exposure impairs dark avoidance memory and synaptic potentiation of ventral hippocampal CA1 during adulthood in rats

Adolescence is a neurobiological critical period for neurodevelopmental processes. Adolescent opioid exposure can affect cognitive abilities via regional-specific lasting changes in brain structure and function. The current study was therefore designed to assess the long-term effects of adolescent morphine exposure on dark avoidance memory and synaptic plasticity of the ventral hippocampal CA1. Adolescent Wistar rats received escalating doses of morphine for 10 days. Morphine injections were started with an incremental dose of 2.5 mg/kg to reach a dose of 25 mg/kg. 30 days after the last injection, inhibitory memory and in vitro field potential recording were evaluated. Also, the weight of the animals was measured during drug and post-drug exposure. We found that adolescent morphine exposure decreased weight gain during morphine and post-morphine exposure. Passive avoidance memory was impaired in the morphine group. Moreover, adolescent morphine exposure caused an increase in baseline synaptic responsiveness and failed long-term potentiation (LTP) in the ventral hippocampal CA1 during adulthood. In the morphine group, the mean values of the field excitatory postsynaptic potential (fEPSP) slopes required to elicit a half-maximal population spike (PS) amplitude were significantly greater than that of the saline group. Therefore, adolescent morphine exposure has a durable effect on memory functions, synaptic activity, and plasticity of ventral hippocampal CA1. Adults with adolescent morphine exposures may experience maladaptive behaviors and cognitive disabilities.

Adolescent alcohol exposure alters threat avoidance in adulthood

Adolescent binge-like alcohol exposure impairs cognitive function and decision making in adulthood and may be associated with dysfunction of threat avoidance, a critical mechanism of survival which relies upon executive function. The present study investigated the impact of binge-like alcohol exposure during adolescence on active avoidance in adulthood. Male and female rats were subjected to adolescent intermittent ethanol (AIE) exposure by vapor inhalation and then tested in adulthood using a platform-mediated avoidance task. After training to press a lever to receive a sucrose reward, the rats were conditioned to a tone that co-terminated with a foot-shock. A motivational conflict was introduced by the presence of an escape platform that isolated the rat from the shock, but also prevented access to the sucrose reward while the rat was on the platform. During the task training phase, both male and female rats exhibited progressive increases in active avoidance (platform escape) in response to the conditioned tone, whereas innate fear behavior (freezing) remained relatively constant over training days. A history of AIE exposure did not impact either active avoidance or freezing behavior during task acquisition. On the test day following platform acquisition training, female rats exhibited higher levels of both active avoidance and freezing compared to male rats, while AIE-exposed male but not female rats exhibited significantly greater levels of active avoidance compared to controls. In contrast, neither male nor female AIE-exposed rats exhibited alterations in freezing compared to controls. Following 5 days of extinction training, female rats continued to display higher levels of active avoidance and freezing during tone presentation compared to males. Male AIE-exposed rats also had higher levels of both active avoidance and freezing compared to the male control rats. Together, the results demonstrate that female rats exhibit elevated levels of active avoidance and freezing compared to males and further reveal a sex-specific impact of AIE on threat responding in adulthood.

Adolescent brain maturation and the neuropathological effects of binge drinking: A critical review

Adolescence is a transitional stage marked by continued brain development. This period is accompanied by physical and neurochemical modifications in the shape and function of the hippocampus, prefrontal cortex, and other limbic system structures. Brain maturation during adolescence, which is typically governed by intrinsic factors, can be dramatically altered by environmental influences such as drugs and alcohol. Unlike many other addictive substances, binge drinking is very common and normative among teenagers and young adults. This repeated pattern of excessive alcohol consumption in adolescents has been shown to cause behavioral changes and neurocognitive impairments that include increased anxiety, risky decision-making, and learning deficits, which could lead to the development of alcohol use disorder (AUD). This manuscript highlights factors that lead to adolescent binge drinking, discusses maturational changes that occur in an adolescent's brain, and then evaluates the effect of adolescent alcohol consumption on brain structure, function, and neurocognitive abilities in both human studies and animal models. The impact of gender/sex and COVID-19 are briefly discussed. Understanding the factors that promote the onset of adolescent binge drinking and its undesirable consequences could serve as a catalyst for developing therapeutic agents that would decrease or eradicate the damaging effects of alcohol on an adolescent brain.

Effects of prenatal opioid exposure on synaptic adaptations and behaviors across development

In this review, we focus on prenatal opioid exposure (POE) given the significant concern for the mental health outcomes of children with parents affected by opioid use disorder (OUD) in the view of the current opioid crisis. We highlight some of the less explored interactions between developmental age and sex on synaptic plasticity and associated behavioral outcomes in preclinical POE research. We begin with an overview of the rich literature on hippocampal related behaviors and plasticity across POE exposure paradigms. We then discuss recent work on reward circuit dysregulation following POE. Additional risk factors such as early life stress (ELS) could further influence synaptic and behavioral outcomes of POE. Therefore, we include an overview on the use of preclinical ELS models where ELS exposure during key critical developmental periods confers considerable vulnerability to addiction and stress psychopathology. Here, we hope to highlight the similarity between POE and ELS on development and maintenance of opioid-induced plasticity and altered opioid-related behaviors where similar enduring plasticity in reward circuits may occur. We conclude the review with some of the limitations that should be considered in future investigations. This article is part of the Special Issue on 'Opioid-induced addiction'.

Long-lasting BDNF signaling alterations in the amygdala of adolescent female rats exposed to the activity-based anorexia model

Introduction: Anorexia nervosa (AN) is a severe psychiatric disorder characterized by a pathological fear of gaining weight, excessive physical exercise, and emotional instability. Since the amygdala is a key region for emotion processing and BDNF has been shown to play a critical role in this process, we hypothesized that alteration in the amygdalar BDNF system might underline vulnerability traits typical of AN patients. Methods: To this end, adolescent female rats have been exposed to the Activity-Based Anorexia (ABA) protocol, characterized by the combination of caloric restriction and intense physical exercise. Results: The induction of the anorexic phenotype caused hyperactivity and body weight loss in ABA animals. These changes were paralleled by amygdalar hyperactivation, as measured by the up-regulation of cfos mRNA levels. In the acute phase of the pathology, we observed reduced Bdnf exon IX, exon IV, and exon VI gene expression, while mBDNF protein levels were enhanced, an increase that was, instead, uncoupled from its downstream signaling as the phosphorylation of TrkB, Akt, and S6 in ABA rats were reduced. Despite the body weight recovery observed 7 days later, the BDNF-mediated signaling was still downregulated at this time point. Discussion: Our findings indicate that the BDNF system is downregulated in the amygdala of adolescent female rats under these experimental conditions, which mimic the anorexic phenotype in humans, pointing to such dysregulation as a potential contributor to the altered emotional processing observed in AN patients. In addition, since the modulation of BDNF levels is observed in other psychiatric conditions, the persistent AN-induced changes of the BDNF system in the amygdala might contribute to explaining the onset of comorbid psychiatric disorders that persist in patients even beyond recovery from AN.

Development of anxiety-like behaviors during adolescence: Persistent effects of adolescent morphine exposure in male rats

Epidemiological studies show the prevalence of opioid use, misuse and abuse in adolescents, which imposes social and economic accountability worldwide. Chronic opioid exposure, especially in adolescents, may have lasting effects on emotional behaviors that persist into adulthood. The current experiments were therefore designed to study the effects of sustained opioid exposure during adolescence on anxiety-like behaviors. Adolescent male Wistar rats underwent increasing doses of morphine for 10 days (PNDs 31-40). After that the open field test (OFT) and elevated plus maze (EPM) test were performed over a 4-week postmorphine treatment from adolescence to adulthood. Moreover, the weight of the animals was measured at these time points. We found that chronic adolescent morphine exposure reduces the weight gain during the period of morphine treatment and 4 weeks after that. It had no significant effect on the locomotor activity in the animals. Moreover, anxiolytic-like behavior was observed in the rats exposed to morphine during adolescence evaluated by OFT and EPM test. Thus, long-term exposure to morphine during adolescence has the profound potential of altering the anxiety-like behavior profile in the period from adolescence to adulthood. The maturation of the nervous system can be affected by drug abuse during the developmental window of adolescence and these effects may lead to behaviorally stable alterations.

Withdrawal: A key consideration in evaluating whether highly processed foods are addictive

Researchers are currently debating whether theories of addiction explain compulsive overeating of highly processed (HP) foods (i.e., industrially created foods high in refined carbohydrates and/or fat), which contributes to obesity and diet-related disease. A subset of individuals consumes HP foods with behavioral phenotypes that mirror substance use disorders. Withdrawal, the emergence of aversive physical and psychological symptoms upon reduction or cessation of substance use, is a core component of addiction that was central to historical debates about other substances' addictive potential (e.g., nicotine and cocaine). However, no one has systematically considered evidence for whether HP foods cause withdrawal, which represents a key knowledge gap regarding the utility of addiction models for understanding compulsive overeating. Thus, we reviewed evidence for whether animals and humans exhibit withdrawal when reducing or eliminating HP food intake. Controlled experimental evidence indicates animals experience HP food withdrawal marked by neural reward changes and behaviors consistent with withdrawal from other addictive substances. In humans, preliminary evidence supports subjective withdrawal-like experiences. However, most current human research is limited to retrospective recall. Further experimental research is needed to evaluate this construct. We outline future research directions to investigate HP food withdrawal in humans and consider potential clinical implications.

Developing an alcohol and other drug serious game for adolescents: considerations for improving student engagement

OBJECTIVES

To explore perceptions of alcohol and other drug (AOD) education and digital game design preferences among Australian adolescents with the goal of identifying key factors to promote engagement in an AOD serious game for Australian secondary school students.

METHODS

Semi-structured focus groups were conducted with 36 adolescents aged between 13 and 18 years. Qualitative data was analysed using thematic analysis.

RESULTS

Participants described heightened engagement with AOD education that incorporated relatable and relevant real-life stories and interactive discussions. They also expressed a desire for learning to focus on practical strategies to reduce AOD harm and overcome social pressure to use AOD. Participants highlighted the importance of incorporating relatable characters and context-relevant scenarios in promoting engagement, and identified social elements, player choice, and optimal challenge as important game design considerations.

CONCLUSIONS

A focus on meaningful realistic scenarios, relatable characters, relevant information and practical skills may promote high school aged students' engagement with AOD educational content. Game designs incorporating social elements and decision-making opportunities may be conducive to promoting engagement and enhancing learning.

IMPLICATIONS FOR PUBLIC HEALTH

Findings from this study can be used by researchers and game designers for the development of future AOD serious games targeted at Australian adolescents.

Gender and Context Matter: Behavioral and Structural Interventions for People Who Use Alcohol and Other Drugs in Africa

Heavy alcohol consumption and other drug use are prominent across Africa and increase the risk of exposure to violence, HIV acquisition, and other life-threatening injuries. This review synthesizes evidence on alcohol and other drug (AOD) interventions in Africa; evaluates the differences between interventions that do and do not specifically target populations that use AODs; and highlights the impact of comprehensive vs. brief interventions and those that address syndemic issues from a gender and contextualized lens. Literature searches were conducted to identify research outcomes of randomized interventions published between January 2010 and May 2022 that address AOD use in Africa. Thirty-five full-text articles were included in this review. Most of the identified research studies were concentrated in a few countries. Most studies were conducted in South Africa. Many of the studies comprised brief interventions. However, the most comprehensive interventions were the most effective for AOD outcomes. Several studies indicated the importance of addressing AOD use alongside gender-based violence, mental health needs, gender roles, and other social determinants that affect health outcomes. Intervening on AOD use and addressing social determinants from a gender and contextually relevant perspective is essential to ensuring the long-term health and well-being of people in Africa.

Cumulative Stressors and Adolescent Substance Use: A Review of 21st-Century Literature

The aim of this review is to assess empirical studies from the last 2 decades that have examined the association between cumulative stressors and adolescent substance use. Cumulative stressors were measured in these studies with adverse childhood experiences or adolescent stressful life events inventories. The 109 articles meeting the eligibility criteria that emerged from the review demonstrated a consistent, yet modest, association between cumulative stressors and adolescent substance use. Of note, several studies found that the associations were moderated or mediated by genetic factors related to cortisol regulation, intrapersonal factors such as low self-control, or interpersonal factors such as peer substance use. The review's findings thus suggest that efforts to reduce the effects of cumulative stressors on substance use could gainfully identify and target these risk moderators and mediators.

Impairment of spatial memory and dorsal hippocampal synaptic plasticity in adulthood due to adolescent morphine exposure

Opioid exposure during adolescence, a crucial period of neurodevelopment, has lasting neurological and behavioral consequences and affects the cognitive functions in adulthood. This study investigated the effects of adolescent morphine exposure in spatial learning and memory and synaptic plasticity of the CA1 area of the dorsal hippocampus. Adolescent Wistar rats received increasing doses of morphine for 1, 5, and 10 days. Acute morphine group was injected 2.5 mg/kg morphine for 1 day, subchronic morphine group for 5 days, with an increasing dose of 2.5 mg/kg and reached to the dose of 12.5 mg/kg and chronic morphine group for 10 days that began with an increasing dose of 2.5 mg/kg and reached to the dose of 25 mg/kg. Then after 25 days and reaching adulthood, spatial learning and memory were evaluated via the Morris water maze (MWM) test. Moreover, we test the electrophysiological properties of dorsal hippocampal plasticity in adult rats by in vitro field potential recordings. Subchronic and chronic adolescent morphine exposure impaired spatial learning and memory in the MWM test. Baseline synaptic responses in the chronic morphine group were increased and long-term potentiation (LTP) impaired in the CA1 area in subchronic and chronic morphine groups. In adulthood, the slope of the field excitatory postsynaptic potential (fEPSP) required to elicit a half-maximal population spike (PS) amplitude was significantly larger in subchronic and chronic adolescent morphine exposure compared to the saline group. Therefore, subchronic and chronic adolescent morphine exposure altered synaptic transmission and plasticity in addition to learning and memory. Long-term morphine exposure during adolescence can interfere with neurodevelopment, making a persistent impression on plasticity and cognitive capability in adulthood.

A Longitudinal Study of E-Cigarette, Cigarette, and Marijuana Use Sequence in Youth

Objective

There is evidence linking youth use of electronic (e-) cigarettes to subsequent cigarette and marijuana use, raising public health concerns. We examined the sequence of use of e-cigarettes, conventional cigarettes, and marijuana in a longitudinal sample of adolescents, to determine if use of e-cigarettes often preceded use of other substances.

Methods

We collected self-reports from 1123 Oregon adolescents (52% female; 37% Hispanic) longitudinally from 8th to 11th grade (8 total surveys) regarding their lifetime (ever use) and current use (last 30 days) of e-cigarettes, cigarettes, and marijuana. If applicable, students also reported the delivery method of their current marijuana use.

Results

Almost 10% of adolescents reported using e-cigarettes prior to use of cigarettes or marijuana, and the majority of these youth initiated use of marijuana, cigarettes, or both by 11th grade. More youth transitioned from e-cigarette use to marijuana use then from e-cigarettes to use of conventional cigarettes. Participants who were co-using e-cigarettes and marijuana in 11th grade had an increased likelihood of consuming marijuana via vaping, dabbing, and edibles, compared to those who were only using marijuana.

Discussion

E-cigarettes were often the first substance used in this longitudinal sample, and more of these youth subsequently used marijuana compared to cigarettes. While research has focused on the progression from e-cigarettes to cigarettes in youth, these findings indicate that more attention should be focused on the subsequent initiation of marijuana.

Administration of the sigma-1 receptor agonist PRE-084 at emerging adulthood, but not at early adolescence, attenuated ethanol-induced conditioned taste aversion in female rats

Ethanol-induced conditioned taste aversion (CTA) is greater in late adolescence or young adulthood than in early adolescence. The role of the sigma receptor system in this age-related difference has not been extensively explored, particularly in female rats. This study assessed the effects of the activation of sigma-1 receptors (S1-R), via the selective S1-R agonist PRE-084, on ethanol-induced CTA at early or at terminal adolescence/emerging adulthood (28 or 56 days-old at the beginning of the procedures, respectively) in female Wistar rats. The modulation of binge-like ethanol intake by PRE-084 was assessed at terminal adolescence. S1-R activation at the acquisition of ethanol-induced CTA attenuated such learning at terminal but not at early adolescence. PRE-084 did not significantly affect ethanol binge drinking in the terminal adolescents. These results highlight the role of S1-R in ethanol-induced CTA and suggest that differential functionality of this transmitter system may underlie age-specific sensitivities to the aversive effects of ethanol.