Andre d.:
My question is, might it be possible that due to the fact that he is been doing yoga for several years, his state of mind is some sort of "preconditioned" regarding spiritual progress ?
Could it be that he might experience a quick progress of insight ?
I'm a bit afraid that he is having good progress in Insight-Meditation, getting some good insights and then falling back into unpleasant states of mind (for example due to realising the impermanence), what on the other hand is counterproductive regarding his therapy!
Hi Andre, the simple answer is yes. Yoga (integration) is a part of the whole ball of wax and thus the focus (mindfulness) which it fosters (physically and mentally) leads naturally to insight. As to your fears about your friend: If he believes that meditation will help him so be it! If you feel confident that this is also a good way to end suffering and believe that despite that great end there are phases along the path that can exaggerate the negative aspects of our experience then you can warn him of that possibility (probability).
I see this whole thing as "therapy". It may be that what he is experiencing already is due to the stages of insight but it could be that he has issues which can best be handled by standard medical paths. Good luck.