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Received May 21, 2017; Revised Jul 25, 2017; Accepted Sep 7, 2017
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1. Introduction
Anxiety is a normal human emotion that serves to alert and enable the person to deal with perceived stressful situation. The anticipatory and adaptive responses stimulated by anxiety when out of proportion to the stressful situation can result in significant psychological and social impairment [1]. Disproportionate anxiety or that occurring in the absence of a stressor can be controlled by pharmacotherapy. However, anxiolytics are associated with problems of habit formation, withdrawal effects, overdosage, or other undesirable effects [2]. A number of randomized and nonrandomized controlled trials have tested yoga as an intervention with respect to anxiety and anxiety disorders [3]. Yoga, a commonly practiced mind-body intervention, involves a combination of physical activity, breathing exercise, and meditation. It is purported to be potentially useful in a number of physical and mental illnesses [4]. However, owing to the diversity of conditions treated and methodological issues in many studies, the evidence to support the effectiveness of yoga in treating anxiety or anxiety disorders, in general, requires further research [3].
Among the various yoga practices, the alternate nostril breathing (ANB) is a fairly simple and commonly performed exercise. The practice of ANB is traditionally considered to relieve mental unrest and promote physical and mental balance [5, 6]. There have been studies to assess the effects of ANB technique on specific physiological and cognitive functions [7]. There is evidence for a balancing effect of ANB on the activity of both cerebral hemispheres [8]. Also, the practice of ANB has been shown to improve visuospatial memory and improve performance in letter cancellation task [9]. A more recent study also showed that ANB exercise produced better cancellation task scores as measured by the effect on P300 auditory event-related potential. Letter cancellation task requires selective...