What happens to the brain under hypnosis

Since 1988, Brian Weiss's bestseller Many Lives, Many Masters has continued to fuel an enduring fascination. The story of Catherine, the patient who allegedly recalled past existences during hypnotic regression—thereby achieving an improvement in her condition—has captivated millions of readers. However, when psychiatry, cognitive psychology, and neuroscience examine the phenomenon through the scientific method, the picture changes: it does not become less interesting, it becomes more complex.

The first step is to separate hypnosis from the content that emerges during a session.

Hypnosis is neither simply sleep nor a loss of willpower: it is a condition of focused attention and heightened responsiveness to suggestions. Clinical research documents its applications, particularly in pain modulation and certain procedural contexts. This, however, does not mean that what is remembered under hypnosis is necessarily true.

This is where memory comes into play. The brain does not function like a digital archive that stores unchanged copies of the past. To remember means to reconstruct: every memory can integrate sensory fragments, emotions, expectations, and information acquired later on. Under highly suggestive conditions, extremely vivid narratives can emerge, perceived as authentic, without their subjective intensity guaranteeing their historical accuracy.

For this very reason, hypnotic regression cannot be considered a reliable tool for proving the existence of past lives. Suggestions, prior knowledge, source-attribution errors, and false memories represent alternative explanations that science must rule out before accepting extraordinary hypotheses.

Yet an interesting question remains: how can we explain the clinical improvement reported in some cases? In medicine, the efficacy of a therapeutic experience does not automatically prove the correctness of the theory used to interpret it. The relationship with the therapist, expectations, emotional processing, anxiety reduction, and the construction of new meanings can yield benefits without transforming a symbolic narrative into a historical fact. It is here that the Weiss case takes on a different value: not as proof of reincarnation, but as a conceptual laboratory on the constructive power of the mind. Hypnosis demonstrates how much attention, expectation, and suggestion can alter subjective experience and even the perception of pain.

Science is not tasked with denying spirituality, nor with turning every inner experience into an error to be corrected. It does, however, have the duty to distinguish what is lived from what is proven, and to keep the question open without confusing it with a conclusion. And this is perhaps the most modern lesson: a story can be psychologically true, clinically significant, and even transformative without being, for that reason, historically real. It is within this boundary that medicine finds its most fertile ground.

Editorial by Prof. Antonio Giordano for the column “Medicina gli Highlights” published in Il Mattino