A self-induced receptive, hypnotic state which is believed to improve the body's ability to help itself. Doctors have long realised that if they suggested to a patient that a particular treatment would work, it often did – a type of placebo effect. Some techniques now make use of this idea. For instance, people can be taught muscular relaxation to control their anxiety states – the BIOFEEDBACK principle.

Schematic diagram of autonomic nervous system. (Left) Sympathetic nerves leaving middle section of spinal cord to connect via the vertebral ganglion (sympathetic trunk) to organs. (Right) Parasympathetic nerves leaving the brain and lower spinal cords to connect to organs.