Disclosed herein are methods, systems, and apparatus for treating a chronic medical condition in a patient. A time of beat sequence of the patient's heart is determined. A regulatory system parameter is determined based on the time of beat sequence. The parameter is indicative of a stress level of the patient's regulatory adaptation systems. The determined regulatory system parameter is compared with a threshold regulatory system parameter value. An electrical signal is applied to a neural structure of the patient to treat the chronic medical condition if the determined regulatory system parameter exceeds the threshold regulatory system parameter value.