PTSD, Mindfulness and Psilocybin

From the article Psilocybin and meditation have same effect on posterior cingulate cortex (that effect being a massive decrease in activity in the PCC):

•  decreased coupling between the PCC and mPFC with psilocybin corresponds with the subjective experience of a less egoic state, or less “self.” 

In a patient whose PCC was resected,

The surgeons reported "the patient reported experiencing no rumination for almost a month after the surgery and to be in a contemplative state with a subjective feeling of absolute happiness and timelessness."