Search Results (454)

This study investigates the return and volatility transmissions between petroleum prices and stock sector indices of 7 net petroleum-exporting and 19 net petroleum-importing countries over the period from January 2005 to September 2018. Given that indices representing sectors of most considered countries are not available, a unique approach is implemented to manually construct sector indices using daily data of 5768 stocks listed in 10 sectors. The VAR-GARCH model is applied that allows to capture bilateral volatility interactions. Furthermore, the estimates of the model are employed to analyse optimal portfolio holdings and hedge ratios. The findings reveal significant volatility transmissions between petroleum prices and stock sector indices of exporters and importers. However, the direction and magnitude of spillover effects are country- and sector-specific. The optimal portfolio weights and hedge ratios indicate that sector indices of Saudi Arabia (net exporter) and China (net importer) offer better opportunities with respect to hedging petroleum price risks. Full article

The literature on derivative pricing in illiquid markets has mostly focused on computing optimal hedging controls, but empirical microstructure studies show that large order flow generates persistent and predictable price effects. Therefore, these controls can themselves induce endogenous market manipulation because traders can internalize the impact of their own trades. We identify the key shortcoming as the absence of a formal separation between a large trader’s informational advantage and the mechanical price impact and temporary cost-of-hedging. To address this gap, we introduce a counterfactual informed observer—an agent who knows the large trader’s strategy but does not face trading frictions—and use this device to isolate informational order-flow effects from mechanical price impact, a distinction explicitly observed in microstructure data. We prove the existence of information-neutral probability measures under which the discounted asset is a martingale for this observer and derive a hedging framework that jointly accounts for transaction costs and permanent market impact. Numerical experiments show that because price pressure and order-flow effects create non-linear execution costs, the optimal hedge for an out-of-the-money call can deviate substantially from the Black–Scholes hedge, with implications for risk management and regulatory monitoring. Full article

Raw material price volatility, freight rates, and foreign exchange all pose significant uncertainty for lithium-ion battery manufacturers, jeopardising procurement planning and financial stability. In this paper, we formulate a discrete Conditional Value-at-Risk (CVaR) optimisation model to design implementable robust hedging strategies for multi-factor cost exposure. Unlike conventional continuous hedge models, which are often severely parameter-sensitive and require frequent rebalancing, the discrete approach takes hedge ratios to be fixed at a finite implementable grid (0%, 50%, 100%) and simultaneously minimises the expected cost and tail risk. We conduct two case studies: the first evaluates the model behaviour under stochastic price shocks using a multi-market simulation data set, and the second subjects the model to stress testing on correlation drift and tail amplification in order to examine systemic robustness. Our results show that, compared with an OLS-based hedge or a fully hedged benchmark, the discrete CVaR framework yields smoother hedge patterns, lower tail losses, and improved liquidity stability; in addition, our results indicate that, when combined with tail-risk penalisation, decision discretisation can endogenously confer robustness to the industrial procurement horizon. This work contributes to the stochastic optimisation literature and provides a practical tool for mitigating volatility in the global lithium supply chain. Full article

Background: Psychedelic-assisted therapy is gaining renewed attention as a potential treatment for various mental disorders. Despite increasing numbers of randomized controlled trials (RCTs) and meta-analyses, a comprehensive synthesis of the evidence across different substances and indications is lacking. This umbrella review aims to evaluate the effectiveness and safety of psychedelic-assisted therapy—primarily psilocybin, MDMA, and LSD—across major psychiatric disorders, including depression, post-traumatic stress disorder (PTSD), and substance use disorders. Methods: We systematically identified and synthesized data from 23 meta-analyses encompassing over 100 primary studies. Outcomes were standardized and re-expressed as Hedges’ g to enable cross-study comparisons. Study quality was assessed using AMSTAR2, and certainty of evidence was evaluated via the GRADE framework. Results: The number of identified meta-analyses differed markedly depending on the substance and clinical indication: psilocybin for depression (n = 9) and MDMA for PTSD (n = 10) had the strongest evidence base, while fewer meta-analyses were available for LSD in alcohol use disorder (n = 2) and depression (n = 2), ayahuasca in depression (n = 2), and MDMA in autism spectrum disorder (n = 2). Psilocybin demonstrated large effect sizes in major depression (Hedges’ g ≈ 1.05), with some evidence of sustained benefits up to six months. MDMA showed very large effects in reducing PTSD symptoms (Hedges’ g ≈ 1.24), often after 2–3 sessions. LSD yielded short-term benefits for alcohol use disorder (OR ≈ 2.0), though effects declined over time. Across studies, adverse events were generally mild and transient, with no consistent signal for serious harm. Considerable methodological variability was observed, including small and sometimes overlapping samples, heterogeneity, risk of bias, and limited long-term data. These constraints should be taken into account when interpreting the overall findings. Conclusions: Current evidence supports the short-term efficacy and safety of psychedelic-assisted therapy for selected psychiatric disorders, particularly depression and PTSD. However, the low methodological quality of studies and most meta-analyses, as well gaps in long-term safety data highlight the need for high-quality studies. Full article

The use of financial derivatives to hedge economic risks presents several operational and financial reporting challenges to corporations. Special hedge accounting treatment is stringent and complex; different accounting treatments may be used for similar instruments, and risk management strategies, expertise, and judgment are necessary in valuing certain instruments; and careful monitoring and internal controls processes and procedures are necessary to ensure that risks are properly hedged. This study examines whether the use and the extent of the use of financial derivatives are associated with audit risk, financial restatements, and internal control weaknesses. Using a sample of over 6000 firms across non-financial industries from 2012 to 2022, I find that derivative use is associated with an increase in audit fees, restatements, and internal control weaknesses. The fair value of total derivatives used is associated with an increase in audit fees and internal control weaknesses. These findings provide evidence on the hidden costs of derivatives; the auditor’s price increased audit risk in audit fees, and the additional resources needed to support derivative hedges expose firms to additional financial reporting and internal control risks. Full article

Background: Mild cognitive impairment (MCI) is a high-risk prodromal stage of dementia. While tablet/computer-based computerized cognitive training (CCT) is widely used, its efficacy and gamification’s role need clarification. Objective: This study aimed to evaluate the effect of tablet/computer-based CCT on global cognition in older adults with MCI and explore the impact of gamification. Methods: We systematically searched five databases for RCTs (through October 2025) involving individuals aged ≥55 with MCI. The intervention was task-based CCT via tablets/computers. Primary outcome was global cognition. We used random-effects meta-analysis and subgroup analyses. Results: Nineteen RCTs (1013 participants) were included. CCT demonstrated a significant, moderate positive effect on global cognition (Hedges’ g = 0.57, 95% CI [0.36, 0.78]). A trend suggesting greater benefits with higher gamification was observed: high (g = 0.71), medium (g = 0.46), and low (g = 0.45) degrees. However, subgroup differences were not statistically significant (p = 0.4333). Results were robust in sensitivity analyses. Conclusions: Tablet/computer-based CCT effectively improves global cognition in MCI. The potential additive value of gamification highlights its promise for enhancing engagement and effects, warranting further investigation in larger trials. This systematic review was registered with PROSPERO (CRD420251231618). Full article

This study investigates cross-market dependence and dynamic hedging performance between the U.S. equity market and major commodity assets across distinct crisis regimes. Using daily data for the S&P 500 index and four key commodities (WTI crude oil, gold, wheat, and natural gas), we examine how market linkages evolve during systemic disruptions by applying Multifractal Detrended Cross-Correlation Analysis (MFCCA) and the q-dependent detrended correlation coefficient. Hedging performance is assessed using optimal hedge ratios estimated under two multivariate GARCH frameworks: the Asymmetric Dynamic Conditional Correlation (ADCC-GARCH) and the Generalized Orthogonal GARCH (GO-GARCH) model. The findings reveal strong multiscale and time-varying dependencies that intensify during high-volatility periods, reducing the benefits of conventional portfolio diversification. Hedging effectiveness proves to be regime dependent and strongly influenced by nonlinear cross-market interactions. The GO-GARCH model captures volatility spillovers and asymmetric co-movements more effectively, delivering superior hedging results compared with ADCC, especially during episodes of extreme market stress. Among the analysed commodities, crude oil and gold offer the most reliable hedging properties, whereas wheat and natural gas show unstable performance due to supply side shocks. These results emphasize the need for flexible, dynamically adjusted risk-management strategies during crisis environments. Full article

This paper tested the use of the surplus efficient frontier (a minimum tracking error portfolio selection method) to select the optimal hedging portfolio that replicates the best Mexican #4 lemon price in a t + 1 and t + 4 week hedging scenario. Using data on the nine most traded agricultural futures in the US from January 2000 to February 2025, we tested hedging effectiveness across 502 futures portfolios in a weekly backtest. The results suggest that a corn and wheat portfolio increases the hedging effectiveness of the lemon price by 0.7033 or 70.33%. A result that, including the impact of trading fees and taxes, leads to a reduction in income risk to a lemon seller in a t + 1 week hedging horizon. The results suggest that a public or private financial institution could take a short position in such a portfolio to provide a hedge at a price that finances the spot/future price difference at minimum cost to Mexican taxpayers. Full article

This paper analyzes the effectiveness of some defensive assets inside global stock portfolios by applying a standard VaR approach to daily data from 2021 to 2024. The 5Y US note is by far the best hedging instrument for single-hedged portfolios, while in multiple-hedged portfolios further VaR reductions are obtained including commodities, utilities, and real estate stocks. Bitcoin’s hedging performance is strongly negative, displaying an average VaR difference of more than two basis points with respect to the best-performing multiple-hedged portfolio in moderately defensive scenarios. This gap implies much higher maximum potential daily losses for Bitcoin’s single-hedged portfolios. Dynamic risk profiles of multiple-hedged portfolios display a smoother pattern than single-hedged portfolios, particularly during turbulent periods corresponding to the start of the Russia–Ukraine war, emphasizing the crucial benefits of higher asset diversification. Full article

Dynamic canal-system scheduling faces the fundamental challenge of determining the optimal reduction in the current period’s water allocation to reserve sufficient water for remaining periods, thereby hedging against potentially greater future water shortages. Although forecast information has been widely incorporated to address this hedging problem, its effectiveness is heavily dependent on forecast accuracy. Integrating abundant historical canal scheduling data with forecast information provides a promising pathway to improve scheduling performance, yet relevant studies remain limited. This study introduces the concept of Target Residual Lump-Sum Water Quota (TRLSWQ) for each time interval and develops a novel “Bi-level, Two-stage” (BT) model for dynamically updated canal-system scheduling that jointly leverages TRLSWQ and forecast information. The model defines clear canal scheduling rules and effectively adapts to the hierarchical structure in canal system scheduling. The model is applied to the summer–autumn irrigation scheduling of the Yongji main canal and six associated sub-canals in the Hetao Irrigation Area, Inner Mongolia, China. The results indicate that compared with the conventional model, the BT model reduces the total water shortage index of sub-canals from 40.81 to 31.44 (a decrease of 22.9%) and increases the utilization rate of the water quota from 89.3% to 92.9% (an increase of 3.9%). Furthermore, this study clarifies the mechanism of canal scheduling deviations caused by forecast errors: early-stage rainfall under-forecasting induces excessive early-stage allocation, leaving no water for later periods, whereas early-stage over-forecasting leads to withheld early allocation and unused residual lump-sum quota in later stages. The BT model effectively balances shortage risks between current and future periods and offers a practical and robust strategy for improving dynamic canal scheduling in irrigation districts. Full article

This study examines the diversification and hedging potential of non-conventional assets like cryptocurrency (Bitcoin), FinTech equities (FINXs), and green bonds (QGREENs) against traditional equity benchmarks, namely the MSCI World and MSCI Emerging Markets indices using daily data from 2016 to 2021. Employing Time-Varying Parameter Vector Autoregression (TVP-VAR), network connectedness analysis, and the Minimum Connectedness Portfolio (MCoP) approach, the study uncovers dynamic interdependencies among these markets. The results reveal that Bitcoin consistently acts as a net receiver of shocks, providing strong diversification benefits during crisis periods, such as the COVID-19 pandemic. FinTech assets show moderate resilience, while green bonds primarily serve as shock transmitters with limited hedging ability. Optimal portfolio weights indicate the highest allocation to Bitcoin, followed by FinTech and green assets, supporting their inclusion in diversified portfolios. Overall, the findings underscore Bitcoin’s superior risk-mitigating role and highlight the strategic importance of digital assets in achieving portfolio stability and sustainability in volatile global markets. Full article

Using a time-frequency and quantile connectedness approach, our study examines the complex return spillovers dynamics between BRICS Plus stock markets, the volatility index (VIX), and the global geopolitical risk index (GPRD). By employing advanced models such as TVP-VAR, quantile connectedness, and spectral decomposition, we demonstrate how these markets interact across different market conditions and periods. Our results indicate that the VIX consistently acts as the dominant net transmitter of shocks, especially during periods of heightened uncertainty such as the COVID-19 pandemic, the Russian-Ukraine conflict, and the Trump-era U.S.-China trade tensions. In contrast, the GPRD functions predominantly as a net receiver of shocks, indicating its potential role as a hedge during geopolitical crises. BRICS Plus markets exhibit heterogeneous behavior: Brazil, South Africa, and Russia frequently emerge as net transmitters, while China, India, Egypt, Saudi Arabia, and the UAE primarily act as net receivers. Spillovers are strongest at the extremes of the return distribution and are mainly driven by short-term dynamics, underscoring the importance of high-frequency reactions over persistent long-term effects. These findings highlight the asymmetric, nonlinear, and state-dependent nature of global financial contagion, offering important insights for risk management, asset allocation, and macroprudential policy design in emerging market contexts. Full article

Oxygen–ozone (O₂–O₃) therapy is widely used for treating lumbar disc herniation. However, controversy remains regarding the safest and most effective route of administration. While intradiscal injection is purported to show clinical efficacy, it has also been associated with serious complications. In contrast, the intramuscular route can exhibit a more favourable safety profile and comparable pain outcomes, suggesting its potential as a safer alternative in selected patient populations. This mixed-method study combined computed tomography (CT) imaging, biophysical diffusion modelling, and a meta-analysis of clinical trials to evaluate whether intramuscular O₂–O₃ therapy can achieve disc penetration and therapeutic efficacy comparable to intradiscal nucleolysis, while minimizing procedural risk. Literature searches across PubMed, Scopus, and Cochrane databases identified seven eligible studies (four randomized controlled trials and three cohort studies), encompassing a total of 120 patients. Statistical analyses included Hedges’ g, odds ratios, and number needed to harm (NNH). CT imaging demonstrated gas migration into the intervertebral disc within minutes after intramuscular injection, confirming the plausibility of diffusion through annular micro-fissures. The meta-analysis revealed substantial pain reduction with intramuscular therapy (Hedges’ g = −1.55) and very high efficacy with intradiscal treatment (g = 2.87), though the latter was associated with significantly greater heterogeneity and higher complication rates. The relative risk of severe adverse events was 6.57 times higher for intradiscal procedures (NNH ≈ 1180). O₂–O₃ therapy offers a biologically plausible, safer, and effective alternative to intradiscal injection, supporting its adoption as a first-line, minimally invasive strategy for managing lumbar disc herniation. Full article

The cumulative global incidence of long COVID is around 400 million individuals, yet effective treatment options remain limited. A recent systematic review published in 2025 highlighted promising results for non-invasive brain stimulation in alleviating long COVID symptoms. Given the growing use of repetitive transcranial magnetic stimulation (rTMS) for people with long COVID, a focused meta-analysis on the therapeutic effectiveness of rTMS is warranted. To address this gap, this protocol outlines the planned procedures for a systematic review and meta-analysis. A comprehensive search will be conducted across CINAHL Ultimate, MEDLINE, ScienceDirect, and Scopus. Retrieved studies will be managed using Rayyan, with two independent reviewers screening titles and abstracts, followed by full-text review. Data extraction will follow PRISMA and Cochrane guidelines using a standardised form, with dual independent extraction and reconciliation of discrepancies. Risk of bias will be assessed using Cochrane RoB 2.0. Meta-analytical procedures will include calculation of standardised effect sizes (e.g., Hedges’ g), use of random-effects models, and assessment of heterogeneity via I², Cochran’s Q, and tau². Subgroup and moderator analyses will explore variations in rTMS protocols, participant characteristics, and symptom domains. Sensitivity analyses and meta-regression will be conducted where data permit. Results will be visualised using forest and funnel plots, and the GRADE framework will be used to assess the quality of evidence. Full article

Background/Objectives: Lumbar degenerative disease drives numerous elective spine surgeries, and anesthetic choice significantly influences airway risk, hemodynamics, analgesia, mobilization, and recovery. Interest in awake lumbar surgery, typically using spinal anesthesia (SA) with light sedation, has grown as comparative studies suggest comparable safety to general anesthesia (GA) with potential reductions in opioid use, nausea, time to ambulation, and efficiency metrics. However, these benefits may be context-dependent under standardized perioperative care. Therefore, the aim of this umbrella review is to synthesize previously published meta-analyses that compare postoperative outcomes between SA and GA in patients undergoing lumbar spine surgery. Methods: A systematic literature search was executed with defined criteria across PubMed, Embase, and Web of Science. Data analysis was performed using the metaumbrella R package to report equivalent Hedges’ g values. Each meta-analysis was evaluated with the AMSTAR2 tool, and the credibility of the evidence was determined with Ioannidis criteria. Results: Seven meta-analyses were included. Pooled data showed that SA was associated with shorter operative time, reduced length of stay, and lower intraoperative blood loss, supported by class III credibility for operative time and length of stay and class IV for blood loss in the setting of high between study heterogeneity. SA was also associated with lower odds of postoperative nausea and vomiting and reduced postoperative analgesic requirements, both graded as class IV with prediction intervals that encompassed the null. Intraoperative hypotension and bradycardia did not differ significantly between SA and GA, and postoperative pain scores and overall complication rates were similarly neutral. Conclusions: This umbrella review identifies potential advantages of SA in lumbar spine surgery, including shorter operative time, reduced length of stay, lower intraoperative blood loss, and lower postoperative nausea and analgesic requirements, while finding no consistent differences in hemodynamic events or overall complications. These findings suggest SA as an alternative pathway to general anesthesia for selected lumbar procedures but highlight substantial heterogeneity and low-to-intermediate credibility for several endpoints, underscoring the need for additional high-quality, protocolized comparative studies to refine effect sizes and define optimal patient and procedural selection. Full article