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Background: Evidence-based psychological interventions exist for individuals with obsessive-compulsive disorder (OCD), but many individuals with OCD are unable to access them because of barriers, such as geographical isolation, treatment cost, and stigma etc. Unguided self-help psychological intervention has emerged as a potential solution to this problem. However, there is limited research on its overall effectiveness. This study aimed to address this gap. Methods: Comprehensive searches from inception to 1st Jan 2023 were conducted in both international (PubMed, Embase, PsycINFO, International clinical trials registry platform of WHO) and Chinese (China National Knowledge Infrastructure, WeiPu, WanFang, Chinese Clinical Trial Registry) databases. The registered protocol is accessible at https://doi.org/10.17605/OSF.IO/FKB5W. We included randomized controlled trials (RCTs) comparing unguided self-help psychological interventions to control groups for individuals with OCD. The primary outcome was OCD symptom severity, with Hedges' g calculated post-intervention. Heterogeneity was deemed to be low, moderate, and high if the I2 value was quantified 25%, 50%, and 75% respectively. Relative Risks (RRs) was calculated for dropout rates post-intervention. Random-effects models were used for all analyses. Results: 12 RCTs comparing unguided self-help psychological interventions to control groups were identified, with a total of 20 comparisons and 769 OCD patients. Overall, unguided self-help psychological interventions demonstrated a significant moderate effect on reducing OCD symptom severity (g = −0.42; 95% CI [−0.69; −0.14]) compared to control groups, with a moderate heterogeneity (I2 = 59%; 95% CI [22.73; 78.38]). This finding remained significant in sensitivity analyses for the self-rated Yale-Brown Obsessive-Compulsive Scale (Y-BOCS; k = 7, g = −0.46; 95% CI [−0.71; −0.2]) and after removing an outlier (g = −0.37; 95% CI [−0.55; −0.19]), but not for the clinician-rated Y-BOCS (k = 4, g = −0.78; 95% CI [−2.75; 1.19]) and Obsessive Compulsive Inventory-Revised (k = 6, g = −0.26; 95% CI [−0.53; 0]). Subgroup analyses revealed a significant difference in effect size between studies conducting intention-to-treat and completers-only analyses (p = .01). The completers-only analyses demonstrated a moderate significant effect (g = −0.65; 95% CI [−1.08; −0.21]), whereas the effect of the intention-to-treat analyses was not significant (g = −0.18; 95% CI [−0.36; 0]). Participants in the unguided self-help groups exhibited a significantly higher dropout rate (RR = 2.08; 95% CI [1.53; 2.81]) compared to control groups. Furthermore, participants recruited from the community had a higher likelihood of dropping out compared to those recruited from clinical settings (p

Objective: This study aimed to examine (1) the independent effects of hypoxia on cognitive function and (2) the effects of exercise on cognition while under hypoxia. Methods: Design: Systematic review with meta-analysis. Data sources: PubMed, Scopus, Web of Science, PsychInfo, and SPORTDiscus were searched. Eligibility criteria for selecting studies: randomized controlled trials and nonrandomized controlled studies that investigated the effects of chronic or acute exercise on cognition under hypoxia were considered (Aim 2), as were studies investigating the effects of hypoxia on cognition (Aim 1). Results: In total, 18 studies met our inclusionary criteria for the systematic review, and 12 studies were meta-analyzed. Exposure to hypoxia impaired attentional ability (standardized mean difference (SMD) = –0.4), executive function (SMD = –0.18), and memory function (SMD = –0.26), but not information processing (SMD = 0.27). Aggregated results indicated that performing exercise under a hypoxia setting had a significant effect on cognitive improvement (SMD = 0.3, 95% confidence interval: 0.14 – 0.45, I2 = 54%, p < 0.001). Various characteristics (e.g., age, cognitive task type, exercise type, exercise intensity, training type, and hypoxia level) moderated the effects of hypoxia and exercise on cognitive function. Conclusion: Exercise during exposure to hypoxia improves cognitive function. This association appears to be moderated by individual and exercise/hypoxia-related characteristics.