Journal of Psychopharmacology

Psilocybin shows therapeutic promise for several psychiatric disorders, but the acute perceptual and cognitive alterations produced by conventional doses (10-25 mg) require in-clinic supervision, which limits scalability. Whether the therapeutically relevant pharmacology of psilocybin can be separated from its hallucinogenic activity remains unresolved. To address this gap, we conducted a Phase 1, randomized, double-blind, placebo-controlled, single ascending dose study to characterize the safety, pharmacokinetics and pharmacodynamics of low doses of psilocybin. Fifty-six healthy adults received a single oral dose of psilocybin (0.5, 1.0, 1.5, 2.5, 3.5 or 4.0 mg) or matching placebo across seven sequential cohorts, with each dose escalation reviewed by a Drug Safety Review Committee. All participants completed the study with no serious adverse events or discontinuations. Treatment-emergent adverse events were comparable to placebo and most prominently arose as somnolence. Plasma psilocin appeared rapidly with a median time to maximum concentration < 1 h with dose-proportional exposure and a short terminal half-life. Subjective drug effects were dose-related and became distinguishable from placebo at doses at or below 2.5 mg. Peak subjective ratings increased with dose, while any signs of hallucinations or altered-states scores remained low and not different than placebo. Psychophysiological engagement was confirmed by a clear dose-dependent pupillary dilation while cognitive performance (attention, vigilance, working memory, impulse control) showed no dose-dependent decrement and state anxiety did not increase at any dose. These findings indicate that the perceptible pharmacology of psilocybin can be dissociated from significant perceptual alterations and cognitive impairment at low doses. They further support controlled investigations in outpatient Phase 2 studies evaluating the safety and feasibility of repeated, self-administered low-dose psilocybin. ClinicalTrials.gov #NCT07710027

BackgroundSerotonergic psychedelics are advancing as psychiatric treatments, yet acute responses vary between individuals and the contribution of sex, a fundamental biological variable, remains largely unexamined. MethodsWe pooled two double-blind, placebo-controlled studies in healthy volunteers (N = 72; 31 male, 41 female) comparing psilocybin 15 mg, 2C-B 20 mg, and LSD 50 {micro}g. Linear mixed models tested sex differences in acute subjective effects (visual analogue scales), retrospective altered-states ratings (5D- and 11-ASC), empathy (Multifaceted Empathy Test), and peak plasma blood concentrations (Cmax, AUC), with treatment, sex, their interaction, as fixed factors, and age as a covariate. ResultsFemale participants reported numerically higher subjective ratings than male participants on most measures. After adjustment for age, sex differences remained significant for feeling under the drugs influence, reduced vigilance, and impaired control and cognition, with medium-to-large effects. These effects were largely consistent across the three drugs. No sex differences emerged on any empathy measure or in peak drug concentrations. ConclusionsFemale participants may experience more intense acute subjective effects and greater perceived impairment under psychedelics, independent of age and not explained by drug exposure. These preliminary findings, implicating pharmacodynamic rather than pharmacokinetic mechanisms, have implications for dosing, informed consent, and safety monitoring, and underscore the need to treat sex as a biological variable in adequately powered psychedelic trials.

Psychedelic drugs are emerging as potentially efficacious tools for treating psychiatric conditions and probing the neural basis of consciousness. Although drug administration context is widely believed to shape psychedelic effects, it remains unclear whether it can independently generate placebo and nocebo effects resembling psychedelic experiences and side effects. In a pre-registered experiment, 78 non-clinical participants inhaled inert medical air under placebo and control conditions while completing a time perception task and a resting-state period. In the placebo condition, the gas was presented as nitrous oxide, whereas in the control, it was correctly identified. Placebo administration increased altered states of consciousness, ego dissolution, dissociation, and side effects, but did not significantly impact time perception. Predictive modelling indicated that placebo-induced psychedelic effects were predicted by trait responsiveness to verbal suggestion and absorption. These findings demonstrate that context alone can induce psychedelic effects, with implications for its causal role in psychedelic action.

Background: The incidence of antidepressant withdrawal reactions in longer-term users and the influence of dosage is insufficiently understood. Objectives: Informed by neuropharmacological models and user surveys, this study examined symptom change during tapering and if increases were specifically associated with reductions below 75% of the minimum effective dose. Design: This was a prospective longitudinal cohort study with seven assessments over six months. Methods: Altogether 32 Swiss adult primary care patients who were on antidepressants for at least six months and in stable remission were assessed at baseline (week 0) before they started tapering and after 2, 4, 6, 8, 16, and 26 weeks. Withdrawal symptoms were measured repeatedly using an adapted version of the Discontinuation-Emergent Signs and Symptoms Scale (DESS) and the main outcome was intra-individual symptom change during intervals. Antidepressant dose was standardized relative to the minimum effective dose in the treatment of depressive and anxiety disorders. Results: Across intervals, reductions below 75% of the minimum effective dose were associated with symptom increases, while reductions above that threshold or no reductions were associated with symptom decreases. After adjusting for potential confounders, the rate of clinically relevant symptom increases contingent on dose reductions below 75% of the minimum effective dose was 33%, as compared to 13% during intervals with no dose reductions (OR=3.2, 1.4 to 7.4). We thus estimated that 60% of the risk of clinically relevant symptom increases was attributable to pharmacological withdrawal effects. The adjusted incidence rates for clinically relevant and severe withdrawal reactions were 32% and 11%, respectively. Conclusions: Consistent with neuropharmacological research findings, we found that antidepressant withdrawal symptoms emerge mostly following reductions below 75% of the minimum effective dose, affecting about one-third of patients. Even small reductions may trigger clinically relevant withdrawal reactions in this lowest dose-range, stressing the need for personalized tapering plans.

Background: Hyperbolic tapering is an increasingly recognized approach for discontinuing serotonin reuptake inhibitor (SRI) antidepressants that involves non-linear dose reductions with equal stepwise reductions in serotonin transporter (SERT) occupancy to mitigate withdrawal symptoms. Its theoretical basis is the hyperbolic relationship between SRI dose and SERT occupancy reported in radioligand imaging studies. Hyperbolic tapering implicitly assumes that changes in SERT occupancy approximate changes in biologic effect and withdrawal risk. Because SERT occupancy plateaus across the therapeutic dose range of SRIs, this framework predicts relatively small biologic effects and withdrawal risk within this range. However, SERT occupancy influences serotonergic activity only indirectly via its effects on extracellular serotonin concentrations, and the relationship between these two variables is poorly characterized. Methods: We developed a two-pathway clearance model derived from mass-action kinetics to evaluate the steady-state relationship between SERT occupancy and extracellular serotonin concentrations under chronic SRI treatment. Results: Our analysis indicates that serotonin concentrations increase hyperbolically as transporter occupancy increases, suggesting that biologically meaningful differences in serotonergic signaling persist across the therapeutic dose range of SRIs despite plateauing occupancy. Conclusions: Our model predicts a hyperbolic relationship between SERT occupancy and extracellular serotonin concentrations, suggesting that changes in occupancy may not map proportionally onto serotonergic effect. These findings provide a potential mechanistic explanation for dose-dependent clinical effects of SRIs despite plateauing transporter occupancy and generate testable hypotheses regarding antidepressant tapering strategies. Empirical validation is warranted.

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.

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.

Sleep is fundamental to metabolic regulation, cognitive performance, immune function, and cardiovascular health, and evening screen exposure is widely proposed as a behavioural contributor whose adult evidence base remains thin. Here we analyze 350,600 paired screen-day and following-night observations from 3,086 Ultrahuman Ring AIR adult users. Sleep quality was assessed via the rings composite sleep score, derived from heart-rate variability, nightly movement, and skin temperature. At the user level, users in the highest screen-time quintile had lower sleep scores (Cohens d = -0.30), shorter sleep duration (d = -0.25), and lower sleep efficiency (d = -0.14) than the lowest screen-time quintile (all q [&le;] 0.005). Further, 45+ min of screen use in the last hour before bed was associated with mean sleep scores at the bottom of the cohort range, whereas the same dose 4-5 hours earlier showed no detectable cost, so the timing of screen use, not just its total, mattered. We next asked whether the way users distribute their screen time across the 24 hours, independent of total dose, separates users by sleep outcome. K-means clustering on 24-hour screen-use profiles identified three phenotypes: Daytime Peakers (DP), Late-Night Users (LNU), and Round-the-Clock Users (RCU), distinguished primarily by their nighttime share of 24-h screen use (DP 8.2%, LNU 16.9%, RCU 29.3%). Despite comparable total daily screen time, the phenotype gap in mean sleep score between DP (75.2 {+/-} 0.3 SEM) and RCU (66.7 {+/-} 0.6) was 8.5 points. We further identified users who transitioned phenotypes across four sequential quarters of follow-up; in this longitudinal subcohort, the magnitude of sleep-score change tracked the magnitude of the behavioural shift, with DP [-&gt;] LNU transitioners declining by 5.16 {+/-} 0.94 points and LNU [-&gt;] RCU transitioners by 4.79 {+/-} 1.87 points (both p < 0.05). Together, these findings position the temporal distribution of screen use, alongside its daily total and its concentration immediately before bed, as a behavioural correlate of objectively measured sleep quality in adults.

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.

Young people with major depressive disorder (MDD) exhibit altered thermoregulation, which has also been linked to vigilance and sustained attention. However, whether peripheral skin temperature is associated with cognitive vulnerability around sleep onset is unknown. We examined the relationship between the distal-proximal skin temperature gradient (DPG) and vigilance in 38 young people with MDD (20.1{+/-}3.7 years, 65.9% female) using an in-laboratory protocol spanning 4h before, to 2h after, habitual sleep time. Participants were classified into DPGwarm and DPGcold subgroups based on being above or below median DPG before sleep onset. Linear mixed models adjusted for age and sex examined psychomotor vigilance task performance across timepoints. The DPGwarm subgroup (n=19) showed significantly worse performance than DPGcold (n=19) across the evening for mean reaction time (RT), reciprocal reaction time, number of lapses, and fastest 10% of RT (all p[&le;]0.003). Significant GroupxTime interactions were observed for mean RT (F(3,90.4)=5.00, p=0.003) and lapses (F(3,93.6)=6.73, p<0.001), with DPGwarm participants showing progressively worse performance approaching sleep onset. At 2h post-habitual sleep onset, DPGwarm participants exhibited slower RT ({Delta}=129ms, p<0.001) and nearly four times more lapses (14.9 vs 4.1, p<0.001). Performance decrements were not accompanied by differences in melatonin timing, subjective sleepiness or mood, suggesting DPG may index cognitive vulnerability independently. Of note, younger age was associated with greater vigilance decrements. These findings demonstrate that elevated peripheral skin temperature before sleep onset is associated with reduced vigilance in young people with MDD, and may therefore have potential utility as a non-invasive thermoregulatory biomarker of cognitive vulnerability.

Abstract Background Ketamine has emerged as an effective rapid-acting treatment for treatment-resistant depression (TRD), producing significant antidepressant effects within hours of administration. Given ketamine's capacity to induce states of heightened neuroplasticity and psychological openness, psychotherapy may represent a meaningful complement to its pharmacological effects - facilitating emotional processing, cognitive restructuring, and the consolidation of therapeutic gains. However, the adjunctive potential of structured psychotherapeutic support in ketamine-based interventions remains largely unexplored. Methods This preliminary, non-randomized, open-label clinical trial evaluated the adjunctive effects of ketamine-assisted psychotherapy (KAP) in an outpatient setting. Forty-six patients with TRD received eight weekly sessions of subcutaneous esketamine (0.5-1.0 mg/kg) and were allocated into two groups: esketamine without psychotherapeutic support (n = 23) and esketamine combined with structured KAP encompassing preparation, dosing accompaniment, and post-session integration (n = 23). Depressive symptoms were assessed using the Montgomery-Asberg Depression Rating Scale (MADRS) and the Beck Depression Inventory-II (BDI-II) at multiple timepoints during treatment and at follow-up assessments up to six months after protocol completion. Results Both groups showed significant reductions in depressive symptoms throughout treatment. The KAP group demonstrated greater clinical improvement by the end of treatment, with between-group differences on the MADRS emerging at sessions 7 and 8. MADRS response and remission rates were 52.2% and 34.8% in the KET group, and 78.3% and 78.3% in the KAP group, respectively. BDI-II scores indicated earlier subjective improvement in the KAP group, with between-group differences emerging as early as the second session and persisting across multiple timepoints. No significant between-group differences were observed during the six-month follow-up, with both groups maintaining symptom reductions comparable to end-of-treatment levels. Conclusions These findings suggest that structured psychotherapeutic support may be associated with early clinical response and remission rates in subcutaneous esketamine treatment for TRD, potentially through facilitation of emotional processing, psychological flexibility, and behavioural change. Further controlled studies are needed to clarify the specific contribution of psychotherapy, investigate the mechanisms underlying this interaction, and optimize integrated treatment approaches for TRD. The trial was registered at https://ensaiosclinicos.gov.br/rg/RBR-1072m6nv . Keywords: esketamine; treatment-resistant depression; ketamine-assisted psychotherapy; innovative therapies.

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.

Serotonergic psychedelics induce altered states of consciousness characterised by profound changes in emotional experience. Although psychedelics modulate autonomic arousal, sympathetic engagement during their affective effects remains poorly characterised. We recorded cardiac, electrodermal, and respiratory activity in 19 participants following inhalation of 20 or 40 mg of freebase N,N-dimethyltryptamine (DMT) under a semi-naturalistic blinded design, alongside time-resolved retrospective phenomenological reports. DMT induced robust increases across all autonomic markers, integrated into a multimodal index that selectively tracked subjective emotional intensity. Dose-dependent divergence followed modality-specific profiles: heart rate and respiratory differences emerged within the first 2 min post-inhalation, whereas electrodermal activity diverged only during the later phase, with higher doses showing prolonged autonomic engagement. DMT thus produces a transient sympathetic activation co-varying with emotional arousal, followed by gradual disengagement accompanied by pleasantness and bliss. By combining time- and cost-effective peripheral physiological measures with time-resolved phenomenological reports, this work contributes to the objective characterisation of psychedelic-induced affective states and provides a methodological basis for future biomarker research in clinical applications.

Background/ObjectivesPersistent cognitive impairments are prevalent in methamphetamine (meth) use disorder and contribute to maladaptive decision-making and increased relapse vulnerability. There are currently no effective treatments for meth-associative cognitive deficits, and their neurobiological underpinnings remain incompletely understood. This study investigated the effects of chronic meth self-administration on episodic-like recognition memory and evaluated whether pharmacological potentiation of metabotropic glutamate receptor subtype 2 (mGlu2) could rescue these deficits. MethodsAdult male Sprague-Dawley rats underwent 7 days of limited- (1h/day) followed by 14 days of extended-access (6h/day) meth self-administration, followed by 30 days of abstinence. Recognition memory was assessed using the object-in-place (OIP) task. A positive allosteric modulator of mGlu2 receptors, LY-487379 (25 mg/kg, s.c.), was administered prior to the memory test. In parallel, changes in total and surface mGlu2/3 protein levels in the prelimbic and perirhinal cortices were evaluated. ResultsRats with extended access to meth self-administration exhibited escalated drug intake and persistent deficits in OIP memory. Administration of LY-487379 reversed this deficit. Total mGlu2/3 protein levels were unaltered; however, meth exposure was associated with a significant increase in surface mGlu2/3 receptor expression in both cortical regions examined. ConclusionsThese results demonstrate that chronic meth produces persistent cognitive dysfunction that can be rescued by mGlu2 receptor potentiation. The observed increase in surface mGlu2/3 expression may represent a compensatory response to chronic glutamatergic dysregulation, but it appears to be insufficient to restore cognitive function alone, without pharmacological enhancement. The current data encourage further exploration of mGlu2 role in stimulant-associated cognitive dysfunction. HighlightsChronic methamphetamine self-administration produced persistent deficits in episodic-like recognition memory in male rats and dysregulation of mGlu2/3 receptors in the prelimbic and perirhinal cortices. Systemic pharmacological potentiation of mGlu2 receptors rescued meth-associated memory deficits. mGlu2 receptor potentiation may represent a promising therapeutic strategy for treating stimulant-associated cognitive dysfunction. Increased surface mGlu2/3 expression may represent a compensatory adaptation to post-methamphetamine glutamatergic dysfunction, but it is not sufficient to restore cognition alone, without pharmacological enhancement.

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.

Psilocybin and other serotonergic psychedelics show therapeutic promise for psychiatric disorders, yet objective neural correlates linking the acute psychedelic state to persisting psychological outcomes remain limited. Electroencephalography (EEG) microstate analysis characterizes the rapid spatiotemporal organization of large-scale brain activity, offering a millisecond-resolution window into neural dynamics. Here, we examined resting-state EEG microstates in 15 healthy volunteers who participated in a double-blind, randomized, placebo-controlled crossover study of psilocybin, using both data-driven (three-microstate) and canonical (four-microstate) analysis solutions. EEG was recorded at five time points spanning pre-drug baseline, peak intoxication, and recovery. Psilocybin significantly increased the number of global field power (GFP) peaks and reduced microstate lifespan while increasing frequency of occurrence during peak intoxication (50-100 min post-administration), consistent with accelerated transitions between brain states. Notably, microstate coverage was largely preserved, with only a transient difference at peak intoxication in the 2-20 Hz band-width, suggesting that access to the repertoire of canonical brain states is broadly maintained despite altered temporal dynamics. Critically, individual differences in microstate dynamics during peak intoxication correlated with both acute subjective experience intensity and self-reported psychological changes measured 28 days post-administration, providing exploratory evidence for a link between acute neural dynamics and longer-term experiential outcomes in healthy volunteers. These findings suggest that psilocybin is associated with altered temporal organization of large-scale brain dynamics with largely preserved microstate coverage, and identify EEG microstates as candidate neural markers for psychedelic-induced alterations in consciousness with potential relevance to therapeutic research.

Regular cannabis use has been associated with alterations in reward-related neural processes, yet findings remain inconsistent and the relationship between neural activity and behavioural performance is not fully understood. The present study aimed to characterise neural and behavioural correlates of reward processing in regular cannabis users (CU) compared with matched non-users (NU) using the Monetary Incentive Delay Task (MIDT). Firstly, we assessed behavioural performance through reaction times, accuracy and monetary earnings to determine whether potential neural alterations were reflected in task performance. Secondly, focusing on reward-related brain regions, we examined group differences in BOLD functional MRI activity during anticipation and outcome phases separately for monetary win and loss conditions. Finally, we explored the association between behavioural performance and neural activation. Our findings indicate that regular cannabis use is associated with altered engagement of key nodes within the mesocorticolimbic circuit during both anticipatory and outcome phases of reward processing, accompanied by impaired behavioural performance. Particularly, compared with NU, CU showed (I) lower striatal activity during anticipation of monetary win and higher ventral striatum and frontal pole activity during anticipation of monetary loss; (II) greater VTA activation during outcome of successful monetary win and loss avoidance and lower frontal pole activity during outcome of unsuccessful loss avoidance; (III) impaired behavioural performance, reflected in lower monetary rewards and a trend towards slower reaction times and reduced accuracy; (IV) disrupted brain-behaviour coupling. Results from this study may help inform future research on the neurobiological mechanisms underlying changes in reward function and the resultant behavioural consequences of cannabis use.

Treatment-resistant depression and anxiety remain major challenges in psychiatry, particularly in female patients, who are disproportionately affected yet remain underrepresented in preclinical ketamine research. The present study investigated short- and long-term anxiolytic effects of acute subanesthetic ketamine administration in female Wistar-Kyoto (WKY) rats, a validated genetic model of treatment-resistant affective dysfunction. Subjects received a single intraperitoneal injection of saline vehicle or racemic ketamine (5, 10, or 15 mg/kg), followed by acoustic startle response (ASR) testing 24 hours and 7 days later. Oxidative stress was assessed using 8-oxo-2'-deoxyguanosine (8-oxo-dG) immunofluorescence in the basolateral amygdala (BLA), prefrontal cortex (PFC), and hippocampus, alongside analysis of parvalbumin-positive (PV+) interneurons. Ketamine treatment produced dose- and time-dependent behavioral effects with 10 mg/kg eliciting the strongest delayed anxiolytic-like response at 7 days, while 15 mg/kg showed more immediate behavioral effects at 24 hours. While ketamine did not alter PV+ cell count, it significantly increased oxidative stress markers globally in the BLA and prelimbic region of the PFC and specifically in the PV+ interneurons in the BLA. The findings suggest that ketamine's therapeutic effects in female WKY rats may involve region-specific modulation of stress circuitry and oxidative signaling rather than gross interneuron loss. Overall, the study provides evidence for sex-dependent and temporally dynamic effects of ketamine in a translational model of treatment-resistant anxiety and depression.

Electroencephalographic (EEG) microstates provide a compact framework for characterizing the temporal organization of large-scale brain activity, yet their sensitivity to altered brain states remains insufficiently explored. In this study, we applied broadband and frequency-resolved EEG microstate analysis to resting-state EEG data from two publicly available datasets acquired under markedly different altered-state conditions: psilocybin microdosing and acute inhaled N,N-dimethyltryptamine (DMT). The aim was to determine whether narrowband microstate analysis reveals structured alterations in resting-state brain dynamics beyond those captured by broadband analysis alone. Psilocybin microdosing was associated with relatively subtle effects, including reduced global field power and frequency-specific alterations in delta- and theta-band microstate parameters, while no significant broadband spatiotemporal changes were observed. In contrast, acute inhaled DMT was associated with broader microstate alterations spanning broadband, delta, theta, and alpha activity, indicating more extensive reorganization of temporal microstate expression. Across both datasets, a descriptive overlap was observed in the delta band, where microstate C showed increased duration and microstate D showed decreased occurrence. Given the substantial differences between datasets in dose, route of administration, temporal dynamics, and study context, these overlapping effects should be interpreted cautiously. Overall, the findings support frequency-resolved EEG microstate analysis as a useful approach for characterizing altered resting-state brain dynamics and for detecting frequency-specific effects that may be obscured in broadband summaries.

Alcohol demand is commonly assessed using hypothetical alcohol purchase tasks (APTs), from which individual demand curves are constructed and yield multiple indices of reinforcing value. Procedurally, APTs can confer participant burden, and existing brief alternatives cannot produce demand curves or derived indices. Thus, we evaluated a novel, adjusting APT that efficiently and idiographically assesses alcohol demand while preserving the benefits of a full task. Adults reporting past-six-month alcohol use (n=897) completed either the adjusting or full APT, the former utilizing a binary-search-style algorithm to administer six prices from the full APT's price set based on level of alcohol demand. The adjusting APT reduced item burden by 49% and produced well-fitting individual demand curves. Average demand intensity and elasticity estimates did not differ significantly by modality, whereas Omax and breakpoint estimates were significantly higher on the adjusting APT, though only by $3 each. All demand indices from both APTs were positively associated with alcohol use and problems, with similar magnitude by modality. Results provide support for the adjusting APT as a brief measure of alcohol demand that retains demand-curve-based indices of reinforcing value.