Meta-analyses suggest that mindfulness interventions have positive effects on mental health. Yet, how mindfulness interventions exert their effects is still largely unknown. Self-reported mindfulness may partially mediate the association between mindfulness interventions and change in self-reported mental health. We present the results of a novel application of three-level meta-analysis on the pre-post intervention data of 146 RCTs of mindfulness interventions (total N = 10,979), probing the efficacy of a broad range of mindfulness interventions and meditation training against active, treatment-as-usual (TAU), and wait-list control groups. We found that self-reported mindfulness not only increased in mindfulness interventions (d = 0.54, 95% CI [0.47, 0.61]), but also in active (nonmindfulness) controls (d = 0.27 [0.18, 0.36]) and wait-list controls (d = 0.10 [0.04, 0.17]; but not TAU controls: d = 0.04 [−0.03, 0.12]). In addition, change in mindfulness accounted for change in self-reported mental health (mindfulness interventions: d = 0.65 [0.57, 0.73]; active controls: d = 0.49 [0.36, 0.62]; TAU controls: d = 0.20 [0.12, 0.29]; wait-list controls: d = 0.22 [0.14, 0.30]) in all treatment and control groups alike. Thus, self-reported mindfulness apparently is no unique mediator of mindfulness interventions. It may either be more universal, merely a correlate of self-reported mental health, or both. Research should focus on the common denominator of mindfulness interventions and clinically relevant constructs with which self-reported mindfulness shares some of its characteristics. Limitations pertain to the indirect evidence of the three-level meta-analytic approach, the self-report nature of the data, and small-study effects, which suggest the presence of publication bias. The risk of bias may have led to the overestimation of effects and results could further be subjected to effects of shared method variance. Public Significance StatementThis meta-analysis suggests that increases in self-reported mindfulness may explain the treatment efficacy of various mindfulness-based interventions, but also of nonmindfulness-based controls. Selfreported mindfulness thus may be no unique mediator of the effects of mindfulness interventions. The current evidence leaves open whether self-reported mindfulness might be a universal mediator of treatment effects, merely reflects changes of self-reported mental health in general, or both.

Introduction: Nimodipine is routinely administered to aneurysmal subarachnoid hemorrhage patients to improve functional outcomes. Nimodipine can induce marked systemic hypotension, which might impair cerebral perfusion and brain metabolism. Methods: Twenty-seven aneurysmal subarachnoid hemorrhage patients having multimodality neuromonitoring and oral nimodipine treatment as standard of care were included in this retrospective study. Alterations in mean arterial blood pressure (MAP), cerebral perfusion pressure (CPP), brain tissue oxygen tension (pbtO2), and brain metabolism (cerebral microdialysis), were investigated up to 120 minutes after oral administration of nimodipine (60 mg or 30 mg), using mixed linear models. Results: Three thousand four hundred twenty-five oral nimodipine administrations were investigated (126±59 administrations/patient). After 60 mg of oral nimodipine, there was an immediate statistically significant (but clinically irrelevant) drop in MAP (relative change, 0.97; P<0.001) and CPP (relative change: 0.97; P<0.001) compared with baseline, which lasted for the whole 120 minutes observation period (P<0.001). Subsequently, pbtO2 significantly decreased 50 minutes after administration (P=0.04) for the rest of the observation period; the maximum decrease was −0.6 mmHg after 100 minutes (P<0.001). None of the investigated cerebral metabolites (glucose, lactate, pyruvate, lactate/pyruvate ratio, glutamate, glycerol) changed after 60 mg nimodipine. Compared with 60 mg nimodipine, 30 mg induced a lower reduction in MAP (relative change, 1.01; P=0.02) and CPP (relative change, 1.01; P=0.03) but had similar effects on pbtO2 and cerebral metabolism (P>0.05). Conclusions: Oral nimodipine reduced MAP, which translated into a reduction in cerebral perfusion and oxygenation. However, these changes are unlikely to be clinically relevant, as the absolute changes were minimal and did not impact cerebral metabolism.

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