Interoception Underlies The Therapeutic Effects of Mindfulness Meditation for Post-Traumatic Stress Disorder: A Randomized Clinical Trial

Mindfulness-based interventions have proven its efficacy in treating post-traumatic stress disorder (PTSD), but the underlying neurobiological mechanism is unknown. To determine the neurobiological mechanism of action of mindfulness-based stress reduction (MBSR) treating PTSD, we conducted a randomized clinical trial (RCT) in which 98 veterans with PTSD were randomly assigned to receive MBSR therapy (n = 47) or present-centered group therapy (PCGT; n = 51; an active-control condition). Pre- and post-intervention measures of PTSD symptom severity (PTSD Checklist) and brain activity measures of electroencephalography (EEG) were assessed, including spectral power of spontaneous neural oscillatory activities during resting and meditation periods, time-frequency (TF) power of cognitive task-related brain responses, and TF power of heartbeat-evoked brain responses (HEBR) that reflect cardiac interoceptive brain responses during resting and meditation. Compared to controls, the MBSR group had greater improvements in PTSD symptoms, spontaneous EEG alpha (8-13 Hz) power in posterior sites, task-related frontal theta power (4-7 Hz in 140-220 ms post-stimulus), and frontal theta HEBR (3-5 Hz and 265-328 ms post-R-peak). Latent difference score modeling found that only the changes in the frontal theta HEBR mediated the MBSR treatment effect. Brain source-level analysis found that the theta HEBR changes in the anterior cingulate cortex, anterior insular cortex, and the lateral prefrontal cortex predicted PTSD symptom improvements. These results indicated that mindfulness meditation improves spontaneous brain activities reflecting internally oriented relaxation and brain functions of attentional control. However, interoceptive brain capacity enhanced by MBSR appears to be the primary cerebral mechanism that regulates emotional disturbances and improves anxiety symptoms of PTSD.