Continued intention and devotion to apply what is being learned is essential.
And you can't just declare PTSD and depression "gone" in the space of a few hour's trip... that's a somewhat over ambitious conclusion. Neither of those disorders are things that are mere instantaneous sensations, but rather disorders that express themselves over extended periods of time in a variety of repeated events.
I doubt any single trip is going to effect an instant "cure"... but the experience CAN be used to instruct the individual, to give them A SENSE OF HOPE at the demonstration that it is POSSIBLE for them to feel well again... that is the true value of what they have experienced.