| Summary: | Anxiety disorders are an important cause of morbidity worldwide. Existing treatments for anxiety disorders have considerable shortcomings and new treatments are needed. Anxiety impairs attentional control through effects on central executive functions, whereas Mindfulness training has effects on executive function and attention. This thesis explores the potential for using mindfulness and transcranial direct current stimulation (tDCS) as treatment modalities for anxiety disorders, beginning with a literature review, and going on to describe a series of investigations in healthy volunteers. The first study compared the effects of two types of mindfulness training: focused attention (FA) vs. open monitoring (OM), on attention network function, using the Attention Network Test (ANT). The second study explored the effects of a strengthened, integrated FA and OM mindfulness training on attention to threat, using an antisaccade task. A third study examined the effects of a single session of guided FA vs. OM mindfulness on attention to threat (measured using an antisaccade task), during inhalation of air enriched with 7.5% carbon dioxide (CO2). The fourth study evaluated the effect of a single session of tDCS on attention network function (measured using the ANT). The final study examined the effect of a single session of tDCS on attention to threat (measured using the antisaccade task), during inhalation of 7.5% CO2. The main findings of these studies are as follows: A literature review demonstrated that Mindfulness-based interventions have a substantial evidence base for efficacy in depression and a growing evidence base in anxiety disorders. A meta-analysis of randomised controlled trials (RCTs) comparing active vs. sham tDCS in depression found that in patients with major depressive episodes, tDCS offers an effective and tolerable alternative to antidepressant medication for those who do not wish to take or cannot take tolerate medication, or cannot tolerate it: current evidence does not support the use of tDCS in treatment resistant depression, or as an augmentation treatment with antidepressant medication or Cognitive Control Training (CCT). There are no published RCTs of tDCS in anxiety disorders. Mindfulness interventions were associated with enhanced executive control function on the ANT, and attenuated the effects of 7.5% CO2 inhalation on anxiety A single session of tDCS was associated with enhanced executive control function on the ANT, but did not protect against anxiety during inhalation of 7.5% CO2. These findings suggest tDCS may be best utilised during the early stages of depression treatment pathways, and have implications for future design of mindfulness interventions for anxiety.
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