Pain has always been, along our evolution, an important signal that allowed us to defend ourselves by the dangers of the environment. Let’s imagine of inadvertently moving our arm towards something that emits a very strong heat: surely, the burning perception we would feel would induce us to avoid that situation in the future. The International Association for the Study of Pain (IASP) defines pain as an “unpleasant sensory and emotional experience that is associated to tissue damage, actual or potential, or that is described in terms of damage”. This type of definition expresses the conception of pain as psycho-somatic experiential unit. In a painful experience, nociception (the transmission and elaboration of painful stimuli by the central nervous system) can’t be dissociated from subjective unpleasant sensations caused by noxious stimuli. For this reason also, a traumatic event often make us feel pain and, accordingly, physical pain is more intense when we think about it. The role of expectation is pervasive in certain kinds of pain and makes its evaluation extremely complex. Thus, it isn’t surprising that hypnotic processes, acting on the cognitive and emotional representations of a situation, can profoundly influence pain perception. Hypnosis revealed to be an extremely useful instrument to treat pain, both acute and chronic. Generally speaking, a hypnotic suggestion consists in an hypnotic induction followed by suggestions in which the person is invited to imagine certain situations.
Imaginative suggestions, on the contrary, consist in imagining certain situations without previous hypnotic inductions.
In a recent study1, the analgesic effect of hypnosis was compared with that of a placebo treatment. 172 volunteers were assigned to 4 different groups:
-          A control group which didn’t receive any analgesic treatment.
-          A placebo group that received a placebo treatment to induce analgesia.
-          An imaginative group that received an analgesic suggestion without no hypnotic inductions.
-          A hypnosis group that received the suggestion after a hypnotic induction.
Results showed that all treated groups felt a pain reduction compared to the control group. Furthermore, hypnotic treatment was more effective compared to placebo and to the sole imaginative suggestion (these two did not show significant differences). It is now clear that the expectation of hypnotically induced analgesia can play an important role in experiencing pain. Additionally, in another experiment that involved imaginative and hypnotic suggestions, researchers have identified specific brain regions that are active during pain inductions2. In this study, subjects underwent a functional magnetic resonance (fMRI) in three different conditions: true thermal pain experience, hypnotic suggestion of thermal pain without any stimulation, imagination of thermal pain without stimulation.
Results showed that hypnotic suggestions activate a brain pattern that is similar to real painful experiences. Interestingly, thalamus – a fundamental cerebral structure involved in sensory perception -, cingulate cortex and prefrontal areas – which are active during attention and emotional modulation tasks – and the insula – responsible for the individual emotional response – activated during the experiment. As opposed to hypnotic suggestion, imagining pain produces minimal activations of the “pain-matrix”, that is, the group of areas that are active during painful experiences.
During hypnotic induction, the activation of brain areas involved in both sensory perception and emotional response of pain demonstrates that hypnosis can profoundly act on cognitive levels and confirms that pain is a complex phenomenon that goes beyond simple nociception.