Hypnosis poses no danger in a safe setting where hypnosis can be the appropriate focus. For example, if we're doing a hypnotherapy session in a room, you're online or listening to a recording in your home, you can ensure it's safe. However, if you're listening to a hypnosis recording whilst walking, driving or on the London Underground, these settings introduce unnecessary risk of accident from missing your tube stop to bumping into things.
You are in control of whether you want to be hypnotized and the depth of your level. Often the level of depth will depend on how trusting and comfortable you feel at the time. You might fall asleep, especially if you're already tired. I have during recordings, but woke up during the rousing phase and felt great.
Statistically, about 10-20% of the population are naturally 'highly suggestible' . I worked with one highly-suggestible client online and found that person more difficult to rouse from hypnosis. It took about 30 seconds longer as I repeated, with increasing volume. She had very good results and we problem-solved steps I could take if she feel asleep.
Whilst training, it was suggested it might be 'riskier' to work with those who've experienced psychosis (i.e. perhaps too 'highly imaginative' in breaking with 'reality'). However, other researchers suggest there's no additional risk (Wagstaff, 2006). Regression may pose additional risks such as emotional overwhelm or other unexpected reactions.
NO! I cannot (and would want to!) control you or take away your free will. The best description of being a good hypnotic state is like feeling on the verge of falling asleep. You are aware you're of your surroundings and starting to drift off.
Having been in hypnosis myself using generic recordings, I can say that when I heard a suggestion that didn't suit me, I was able to think to myself "What?! No, I don't think I agree with that.... hope the next statement is better....' (and it was). You are awake enough to still decide. The benefit of personal hypnotherapy is we craft everything specifically to you BEFORE the hypnosis.