i see. I've experienced panic attacks at the end of two psilocybin trips, which i attribute solely to excessive thc ingestion.
I think it is possible that, because psilocybin increases hippocampal neurogenesis and fear response learning, this can go both ways. With a profoundly positive trip, you can have extinction of fear. and with a deeply negative experience, you can have a stronger learned fear response than before.
however, i still think that it possesses potential for ptsd treatment. there is more and more research coming out in favor of its anxiety-ameliorating effects. from unadulterated psilocybin itself, i think that it is rather hard to have a negative experience (assuming set and setting are appropriate, as this is extremely important). At least for myself, I am planning on a "hair of dog" approach, and will be re-ingesting soon, in hopes of extinguishing my habituated fear responses. I think that psilocybin has this potential because, on my second "bad trip" i experienced a major reduction in anxiety/panic symptoms, and it was only until co-ingestion of thc that i relapsed.
Here are a few references as to why psilocybin may be effective in this respect:
http://www.scienceda...40507095756.htm - Psilocybin inhibits the processing of negative emotions in the brain
www.biologicalpsychiatryjournal.com/article/S0006-3223(14)00275-3/abstract - Psilocybin-Induced Decrease in Amygdala Reactivity Correlates with Enhanced Positive Mood in Healthy Volunteers
http://www.ncbi.nlm....pubmed/23727882 - Effects of psilocybin on hippocampal neurogenesis and extinction of trace fear conditioning.
Obviously, this is a scary route for someone that is suffering directly as a result of their psychedelic substance use. however, i think that with appropriate set, setting, and research, it can be a wholly beneficial experience. Of course, this advice is only directed towards psilocybin use, and the use of any other chemical for treatment would not be recommended. I would strongly advise reading this text as preparation for any trip - http://www.sacred-te...tib/psydead.htm
Outside of re-ingesting psychedelics, exercise is probably the best alternative (/supplementary option). There is a large body of evidence indicating that cardio exercises significantly increase hippocampal neurogenesis, speeding up the process of conditioned fear learning (and extinction). Ultimately, you can't go wrong with exercising more.
http://www.scirp.org...23#.U9bonhbWFWk - Reduction of Fear by Intense Aerobic Exercise Approaching Physical Exhaustion
http://www.sciencedi...16643280900610X - Voluntary exercise improves both learning and consolidation of cued conditioned fear in C57 mice
http://www.ncbi.nlm....pubmed/15869081 - The impact of an exercise program on posttraumatic stress disorder, anxiety, and depression.