The vagus nerve is a key component of the parasympathetic nervous system, regulating diverse systemic effects such as digestion, heart and respiratory rate, immune function, and more.  It is considered part of the "rest and digest" aspect of the nervous system, versus that of the sympathetically driven "fight, flight, or freeze" response.  When our systems are in balance, both aspects of the nervous system work together for optimal health and well-being.  But when balance is disrupted, under-activation of the vagus nerve can result in systemic effects: digestive disruption; vasovagal problems including syncope and orthostatic changes; dysregulation of heart and respiratory rate, blood pressure and blood sugar; headaches and pain throughout the body especially neck, back, and abdomen; and altered response to stress, increasing the potential for anxiety and affecting other components of mental health and wellbeing.