Easy to use, cost-effective methods and devices for evaluating and treating stress and thereby disorders caused or exacerbated by stress are provided. More particularly methods and devices for identifying RSA waves during respiration which provide a subject with real-time RSA wave information are provided. These methods and devices also can be used to identify drop points in RSA waves. Such methods and devices provide subjects with the ability to maintain parasympathetic outflow and thereby prevent and/or reduce levels of stress.