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PubMed2026

Effects of six weeks of guanidinoacetic acid supplementation with and without creatine monohydrate on cognitive function and markers of health in healthy adults.

BACKGROUND: Guanidinoacetic acid (GAA) supplementation has been reported to increase brain creatine content more effectively than creatine monohydrate (CrM). However, the effects on cognitive function are unclear. PURPOSE: The purpose of this proof-of-concept exploratory clinical trial was to determine whether GAA supplementation with and without CrM affects cognitive function and/or markers of health. METHODS: In a double-blind, randomized, and counterbalanced manner, 58 healthy and active adults (33 females, 35.5 ± 14 years, 76.2 ± 14 kg) ingested a PLA (PLA, 2 × 6 g/d maltodextrin), GAA (2 × 1 g/d) + PLA (2 × 5 g/d), or GAA (2 × 1 g/d) + CrM (2 × 5 g/d) for six weeks. The participants donated fasting blood samples and completed a battery of tests and questionnaires assessing various aspects of function, mood, stress, sleep quality, and markers of health at baseline and after six weeks of supplementation. Data were analyzed using General Linear Model (GLM) multivariate and univariate with repeated measures, and mean changes from baseline with 95% confidence intervals, and Chi-squared analysis, and considered significant when the probability of error was 0.05 or less, and approaching significance (p > 0.05-p < 0.10). RESULTS: GAA supplementation tended to improve overall reaction time (-241.8 ms [-533, 50], p = 0.10) while significant interaction effects were observed in overall reaction time (p = 0.031-330 ms [-629, -31]) and YES reaction time (-290 ms [-484, -96], p = 0.004) while recalled correct reaction time (-178 ms [-374, 21], p = 0.078) and recalled correct YES (7.4 % [-1, 15.8], p = 0.084) approached significance compared to PLA. Limited to no effects were observed on the Delayed Picture Recognition Task Test, Digit Vigilance Task Test, Corsi Block Task Test, or Stroop Color-Word Task Test. The amount of time engaged in moderate physical activity was significantly greater (p < 0.05) in the GAA group compared to PLA. Participants in the GAA group reported a lower frequency of controlling irritations (p = 0.036), and feeling like difficulties are mounting (p = 0.053) on the Perceived Stress Scale. Some positive and potentially undesirable effects were observed in sleep quality assessments. The quality of life assessment revealed that participants in the GAA group reported less frequent feelings of being worn out (p = 0.068) and that their health was excellent (p = 0.092) while those in the GAA + CrM group reported more frequent limitations when bending, kneeling, or stooping (p = 0.053), more often feeling full of life (p = 0.081), and less frequency in feeling downhearted and depressed (p = 0.066). No clinically meaningful changes were observed in blood markers or self-reported side effects among the groups. CONCLUSION: Dietary supplementation with GAA (2 g/d) and the combination of CrM (10 g/d + GAA 2 g/d) for six weeks improved delayed verbal episodic recognition memory and retrieval speed and some measures of perceived stress, sleep quality, and quality of life. However, most cognitive tests were not affected, particularly when comparing the GAA to the PLA group; there were some inconsistencies in the findings, and several differences only approached significance. Additional research is needed before conclusions can be drawn. Clinical trial registration: ISRCTN68542582.

Humans↗

PubMed2026

Effects of carbohydrate mouth rinse on psychophysiological responses, kinematic variables and technical actions during small-sided soccer games.

BACKGROUND: This study investigated the effects of carbohydrate mouth rinsing (CHOMR) on various psychophysiological, kinematic, and technical actions during 4-a-side small-sided soccer games (SSGs). METHODS: In a randomized, crossover, double-blind design, 16 young male soccer players (age: 15 ± 1 years; height: 172.6 ± 7.0 cm; body mass: 57.8 ± 7.9 kg) participated in two 4-a-side SSGs separated by one week following either CHOMR or placebo (PLA). During each SSGs, heart rate (HRmean, %HR, and HRmax), rating of perceived exertion (RPE), enjoyment, visual analogue scale (VAS) to perceived mental fatigue, mood states, total distance (TD), high-speed running distance (HSRD), average metabolic power (AMP), high metabolic load distance (HMLD), sprint distance (SD), acceleration (ACC), deceleration (DEC), and technical actions (e.g. passing, tackling, shooting, and interceptions) were assessed. RESULTS: Compared with PLA, CHOMR resulted in significantly higher RPE (p = 0.025, g = 0.86) and significantly lower VAS scores (p = 0.010, g = -0.71). In addition, the CHOMR condition showed significantly higher values for interceptions, successful tackles, unsuccessful tackles, unsuccessful shots, and goals (p < 0.05, g = 0.96-2.02), whereas block values were significantly higher in the PLA condition. There were no statistically significant differences in HRmean, %HR, HRmax, enjoyment, TD, HSRD, AMP, HMLD, SD, ACC, DEC, successful passes, unsuccessful passes, successful shots, or mood states between the conditions (p > 0.05). CONCLUSION: The current study findings suggest that CHOMR may enhance selected technical actions and lower VAS scores during 4-a-side SSGs, although it was also associated with higher RPE and did not alter the kinematic responses. In conclusion, CHOMR was associated with higher RPE, lower mental fatigue, and selective improvements in technical actions, with no significant effects on kinematic variables or HR.

Humans↗

PubMed2026

Efficacy and Safety of Psychedelic Microdosing on Psychological Outcomes in Healthy Adults: A Systematic Review and Meta-analysis.

BACKGROUND: Psychedelic microdosing has gained increasing popularity for enhancing mood and cognition, yet its effects on psychological outcomes in healthy adults remain unclear. We aim to evaluate the efficacy and safety of psychedelic microdosing on psychological outcomes in healthy/non-clinical adult population. METHODS: This review was registered in the International Prospective Register of Systematic Reviews (PROSPERO; CRD420251035294). We searched Embase, MEDLINE, and PsycINFO from inception to February 2026 for original studies in healthy adults using sub-hallucinogenic psychedelic doses on separate days. We included randomized studies, nonrandomized prospective studies, cross-sectional studies, and observational longitudinal designs and stratified meta-analyses by design. Random-effects models were used; safety in randomized controlled trials (RCTs) was pooled as risk differences (RDs). Risk of bias was assessed using the Joanna Briggs Institute (JBI) critical appraisal tools appropriate for each study design. RESULTS: 24 studies (3,681 participants) met inclusion criteria, 6 contributed to meta-analyses. RCTs of psilocybin and LSD microdosing showed subjective and neurophysiological effects but minimal impact on cognition, creativity, or sustained mood. Psilocybin altered EEG and speech with little behavioral change, while LSD caused transient mood and minor physiological effects without lasting cognitive or personality benefits. Observational studies indicated mood and personality improvements, likely influenced by expectancy or lifestyle factors. Meta-analyses included two parallel RCTs (3 comparisons; n = 117) and three non-RCT studies (n = 1,013). Adverse event analyses included two RCTs (4 comparisons; n = 109). RCTs showed no clear evidence of immediate symptom reduction: depressive symptoms (SMD = -0.19; 95% CI -0.56, 0.19; I2 = 0%), anxiety (SMD = -0.20; 95% CI -1.11, 0.71; I2 = 82.3%),and stress (SMD = 0.02; 95% CI -0.39, 0.43; I2 = 0%). Non-RCT within-arm estimates were imprecise and heterogeneous for depressive symptoms (SMCC -0.33; 95% CI -0.75, 0.08) and anxiety (SMCC -0.29; 95% CI-0.84, 0.26). Exploratory pooling across all designs suggested decreases in depressive symptoms and stress, while anxiety remained uncertain. Adverse event risks were similar between treatment and control. CONCLUSIONS: Microdosing does not show consistent immediate benefits for depressive, anxiety, or stress symptoms in healthy adults, and evidence from RCTs remains inconclusive. Although improvements were observed in some studies, these effects were not significantly different from placebo. Larger, well-designed RCTs are needed to clarify the efficacy and safety of psychedelic microdosing beyond placebo.

Humans↗

PubMed2026

Effectiveness of transcranial direct current stimulation with and without positive mood induction on worry and transdiagnostic cognitive-emotional processes: A randomized controlled trial.

The present study investigated the effectiveness of transcranial direct current stimulation (tDCS), with and without positive mood induction, on worry and key transdiagnostic cognitive-emotional processes, including attentional bias, working memory, problem solving, and emotion regulation, in individuals with high levels of worry. This single-blind randomized controlled trial included 45 individuals with high levels of worry. After a structured clinical interview, participants were randomly assigned, with gender balancing, to one of three groups: (1) tDCS alone, (2) tDCS combined with positive mood induction, or (3) a sham control group. Outcome measures were administered at three time points (pretest, posttest, and one-month follow-up) and assessed attentional bias (Dot Probe Task), working memory (1-back task), problem solving (Tower of London task), emotion regulation (Gross's Emotion Regulation Questionnaire), and worry severity (Penn State Worry Questionnaire; PSWQ). Repeated-measures ANOVA showed that both active groups (tDCS alone and tDCS + positive mood induction) significantly improved attentional bias, worry, working memory, problem solving, and emotion regulation compared to controls (p < 0.05). The combined intervention produced significantly greater gains than tDCS alone in working memory, problem solving, emotion regulation (p < 0.05), and reductions in attentional bias and worry (p < 0.001). All effects persisted at one-month follow-up (p < 0.05). tDCS reduces worry and attentional bias and enhances cognition and emotion regulation in individuals with high levels of worry. The combined intervention produced larger and more sustained improvements than tDCS alone across the assessed behavioral outcomes. These findings support further investigation of combining tDCS with structured positive mood induction while the mechanisms underlying the additional benefits remain to be established.

Humans↗

PubMed2026

Affective reactivity to a remote computer-based Trier Social Stress Test during a planned quit attempt: associations with short-term cigarette smoking lapse risk.

BACKGROUND: The Trier Social Stress Test (TSST) elicits affective responses and has been linked to smoking behavior. However, its remote use during a planned quit attempt-when stress reactivity may influence early lapse-remains understudied. OBJECTIVE: To quantify affective reactivity to a remotely administered TSST on a planned quit date following overnight abstinence and evaluate associations with cigarette use and lapse within 48 h. METHODS: This secondary analysis used data from a randomized controlled trial of adult smokers completing a remotely administered TSST following overnight nicotine abstinence. Urge, anxiety, and stress were assessed using visual analog scales and summarized using area under the curve (AUC) metrics. Smoking outcomes included cigarette count and lapse within 48 h. Associations were estimated using generalized estimating equations. RESULTS: In adjusted models, anxiety reactivity-but not urge or stress-was associated with cigarette count and lapse. Greater anxiety exposure (AUCtot) and change above baseline (AUCab) were associated with higher cigarette count (IRR=1.0004, 95%CI:1.0002-1.001, p=.002; IRR=1.01, 95%CI: 1.002-1.01, p=.002) and increased odds of lapse (OR=1.001, 95%CI: 1.0001-1.002, p=.03; OR=1.02, 95%CI: 1.001-1.03, p=.03). Effect sizes were small. CONCLUSIONS: Anxiety reactivity under nicotine deprivation was associated with increased cigarette use and lapse 48 h post quit attempt, suggesting individual differences in stress-evoked anxiety may serve as a behavioral marker for early lapse. Remote TSST administration appears feasible for eliciting affective responses on a quit date.

Humans↗