Psilocybin use results in an increase in positive mood by decreasing activation of the amygdala

Psilocybin-Induced Decrease in Amygdala Reactivity Correlates with Enhanced Positive Mood in Healthy Volunteers 
Conclusion:  These results demonstrate that acute treatment with psilocybin decreased amygdala reactivity during emotion processing, and that this was associated with an increase of positive mood in healthy volunteers. These findings may be relevant to the normalization of amygdala hyperactivity and negative mood states in patients with major depression.
Kraehenmann R, Preller KH, Scheidegger M, Pokorny T, Bosch OG, Seifritz E, Vollenweider FX. 
Biol Psychiatry. 2014 Apr 26. pii: S0006-3223(14)00275-3. 
PMID: 24882567 
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This research was conducted by the Department of Psychiatry, Psychotherapy and Psychosomatics, Psychiatric Hospital, University of Zurich, Switzerland.  Among the well know academics associated with this institution is Carl Jung.

Do individuals with PTSD experience depression or negative thoughts?  Might psilocybin, given therapeutically with the proper mindset and in a supportive environment, assist in their recovery? Research in this area needs to be furthered by those who have a responsibility for treatment of individuals with PTSD.

The amygdala is hyperactive in those with PTSD.  "The amygdalocentric model of PTSD proposes that it is associated with hyperarousal of the amygdala and insufficient top-down control by the medial prefrontal cortex and the hippocampus in particular during extinction. This is consistent with an interpretation of PTSD as a syndrome of deficient extinction ability." (Wikipedia: PTSD)

So how does the amygdala relate to mindfulness?  The passage below may shed some light on this matter.

"Mindfulness mediation is designed to alter peoples’ perception of the world by making them disengage from ruminations and attention to negative thoughts and become aware of and accept thoughts non-judgmentally without trying to change them. An 8-week course of mindfulness meditation increased grey matter in brain regions involved in learning and memory, emotion regulation, self-referential processing and perspective taking in healthy people. In stressed individuals, the decrease in perceived stress after an 8-week course of mindfulness meditation was associated with a decrease in the right basolateral amygdala grey matter density. If the changed perception of the world brought about by mindfulness meditation over a period of 8 weeks can cause changes in the brain, this raises the possibility that the change in perception due to psilocybin may result in changes in the brain over a matter of weeks. How such brain changes may interact with the changes in psychology is not known. There is need for more work on the long-term psychological changes associated with psilocybin, as well as research on the long-term brain changes and their possible association with the psychological changes." (From: Young SN. J Psychiatry Neurosci. 2013 Mar;38(2):78-83. Review.)

Psilocybin appears to be uniquely structured (structure determines function) to calm those areas of the brain that are overactive in those suffering from PTSD, plus its effects are long lasting.  If there is another substance or therapy that has similar or better potential, I'd sure like to read about it.