Increased epoch-to-epoch parasympathetic cardiac regulation in participants with posttraumatic stress disorder compared to those with panic disorder and control participants.

•Posttraumatic stress disorder (PTSD) is marked by low respiratory sinus arrhythmia.•Traditional respiratory sinus arrhythmia estimates overlook moment-to-moment shifts.•Time series analysis can model more moment-to-moment shifts in parasympathetic activity.•Chronic hyperarousal may promote upregulatory parasympathetic activity in PTSD.