There have been several threads about the "DANGERS' of qigong. Or about 'Qigong Psychosis'. Etcetera.
Dr. Yang's book ALL discuss the general dangers of incorrect Qigong practice.
Im just a beginner myself, but it seems to me that people, in general, enjoy negativity. These 'problems', and 'dangers', make their lives seem more exciting, and help them to remain in a state of confused ignorance where they are not actually training anything, and are able to continue to delay facing true reality and looking inward.
It is also more 'dramatic' to discuss this negativity than to sit in Qigong meditation, or train some Internal Art technique, and actually experience their Internal side which generally leads to more introspection than speculation or needless worry.
No offense to you John.
Better to read a lot and answer these questions until you have no doubt and understand what you intend to train. And then train in the way described by the Masters before worrying too much.
One thing I suggest to ANYONE interested, is to start with candle training. Light a candle in a dark room and stare at it. Don't think of anything else but following the flickering light with your eyes, and focusing on the in and out of deep breathing. Don't think yet at all about Qi or channels or Qigong, or of any 'words' or 'concepts' at all for that matter. Somehow, the experiences gained through this exercise builds a foundation for moving on to conciously circulating your Qi and storing it. Eventually you don't need the candle anymore to reach this state of focused awareness. I suggest that THAT's when you should start training Qigong.
The internal arts are thousands of years old. Internal martial arts like Xingyi and Bagua are not meant to be trained without their Qigong techniques.
Qigong means 'Energy Work'. This is not a mysterious thing. The energy in your body keeps you alive. Its not scary. Qigong is the art of turning your attention inward, being aware of your energy, and learning to enhance its natural function.
IF you train for a while (months or years depending) and are actually able to store significant Qi in your Dan Tian, it can at that time become dangerous to haphazardly start leading Qi through your body, if you don't know the theory behind it. However, it is unlikely that you will store the required Qi for it to become dangerous if you don't know the theory of Qigong, so there is little need for concern.
Dangers include forcing Qi through the channels before they are given time to gradually widen, or allowing excess Qi to go into the legs and fry the nerves during sitting Qigong. Never lead Qi to the heart, it is usually too Yang already. It is generally considered dangerous to lead Qi up the Spine (Wind Path) or into the brain until you are Intermediate or Advanced. If you don't have a teacher, it is best to just do Wai Dan qigong, unless you truly understand all of the theory.
Or so I read.
"Avoid Prejudice, Be Objective in Your Judgement, Be Scientific, Be Logical and Make Sense, Do Not Ignore Prior Experience." - Dr. Yang