Psychological and attentional outcomes following acute mindfulness induction among high anxiety individuals: A systematic review and meta-analysis

Training outcomes of mindfulness interventions for anxiety have been extensively researched. Less is known about the acute effects of mindfulness induction and associated mechanisms. This systematic review aimed to identify 1) the effect of mindfulness induction on pre-post measures of state anxiety and attention among adults experiencing high levels of anxiety; and 2) the impact of predictors, mediators and moderators on post-induction changes in anxiety and attention. State distress and mindfulness were included as secondary outcomes. A systematic search was conducted in November 2021 in electronic databases using relevant search terms. Five studies (four randomised controlled trials and one non-randomised controlled trial) were included, comprising a total of 277 participants with elevated trait/generalised anxiety. Each study used a brief audio-based mindfulness induction exercise. The meta-analysis indicated mindfulness induction had medium and large effects on state anxiety (k = 3, n = 100, g = −0.60, 95%CI [-1.04, −0.16]; p = .008) and state mindfulness (k = 2, n = 110, g = 0.91, 95%CI [0.52, 1.30], p < .001), respectively, when compared with non-therapeutic control conditions. Furthermore, two studies showed small and moderate effects of mindfulness on state anxiety when compared to therapeutic active controls, but were not pooled in a meta-analysis. While results could not be pooled for attention, there was limited evidence of behavioural improvements on tasks measuring aspects of attention following mindfulness induction. However, one study found an increase in Low Beta to High Beta ratio and a reduction in Beta activity in the Anterior Cingulate Cortex following mindfulness induction. Moreover, another study found aspects of state mindfulness mediated reductions in state anxiety. A small number of studies were included in the review, with high risk of bias and low certainty of evidence present. The findings support the use of mindfulness induction to reduce state anxiety in anxious individuals but suggest gains in state mindfulness may be a more realistic expected outcome. Further controlled trials are needed to delineate the relative effects of objectively assessed anxiety outcomes from mindfulness induction in clinically defined samples.