If you consider something as dangerous is of course a matter of definition.
In a certain way everything in this world is dangerous: Driving a car, travelling by train, leaving the house...
Maybe we should ask:
What's the most dangerous thing that might happen when you are trying lucid dreaming?
And how many people actually experience it?
I was searching literature about this topic and I found some information about this topic. Paul Tholey writes in his very readable book 'Schöpferisch Träumen' (which has unfortunately not been published in English) as follows:
- As a guide of lucid dreaming groups with students and interested volunteers he accompanied a lot of people having lucid dreams. None of them had long lasting problems. Also the lucid dreamers known from history (e.g. Ann Faraday) got benefits from learning lucid dreaming. The dreamers became more courageous, creative and got interesting insights into their own psyche.
- Usually lucid dreams go together with very pleasant feelings.
Sometimes dreamers have unpleasant experiences in lucid as well as in nonlucid dreams. But according to my own experience the most unpleasant thing in a lucid dream is hearing facts about myself which I simply don't want to hear.
Becoming lucid in a nightmare usually turns the experience from a frightening to an interesting and joyful one. Paul Tholey reports about a dreamer who dreamt being chased by a tiger. After becoming lucid he decided to face the beast and finally it transformed into his father.
- Spontaneous lucid dreamers experience the fact of knowing that they are dreaming as a feeling of being locked into a state, not knowing how to get out.
But if you know about the phenomenon of being aware that you are dreaming, there is no need to worry about not waking up any more:
Lucid dreams at beginners level take part at the REM-state which is limited in time. After 10 to 40 minutes REM-sleep is over and the dreamer either wakes up or enters a state of deep sleep.
Experienced lucid dreamers probably developed their own methods for waking up. But most probably they don't want to.
Sleep paralysis is a state of half sleeping, being half awake in which your body is sleeping and paralysed and your mind is fully awake, sometimes starting to dream.
People who experience this state with no knowledge about it feel fear and start to panic, which even stabilizes this state.
According to some non-representative polls in Germany's biggest lucid dreamers community (Klartraumforum.de) the opposite of this claim might be true:
Lucid dreaming doesn't further unintentional sleep paralysis but makes it less likely to occur.
First: Knowing about the nature of sleep paralysis makes it appear less threatening. Most dreamers who struggled with sleep paralysis had less problems after learning lucid dreaming.
Schöpferisch Träumen by Paul Tholey (German Edition) at Amazon.com