Usually the side effects from hypnosis are powerful personal change and a sense of well being. Hypnosis is a totally naturally occurring state of mind, so side effects are rare.
The side effects that do happen, tend to be related to a rest/relax response (parasympathetic response). For example, someone might experience the heart rate slowing down, the blood pressure reducing, the person might perceive time speeding up or slowing down.
Because of these changes, I generally recommend that people do not stand up too quickly immediately after trance, as standing too quickly could cause dizziness or a headaches in rare cases. As long as the person hypnotized spends several seconds to several minutes allowing themselves to transition from the hypnotic state to a regular state, the side effects from emerging are incredibly rare.
Rarely, when profound change work takes place, there can be an effect that can last up to several hours after the end of the hypnosis session. While the brain is integrating change at the deepest level the client may notice up to several hours of difficulty concentrating. I have never had a client report this feeling lasting longer than 2 to 3 hours. I have only ever had a client experience this feeling after positively making a powerful personal change.
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