Tapping into a trance: The neuroscience of hypnosis

Can I hypnotize you in 500 words? Probably not — this isn’t a movie or Vegas stage show — but a professional may be able to in just one. 

Hypnosis is a trance-like state during which the brain experiences a noticeable change in theta wave activity. Theta waves are brain waves synonymous with the subconscious mind, and they are highly active during REM sleep. Although we normally associate hypnosis and sleep with relaxation, nightmares are proof that they are not corequisite, just commonly together.

Hypnosis begins with induction, the process of converting a patient from a waking, conscious state to a trance. The most common induction centers around relaxation. For instance, a guided meditation in which the patient is given a visual aid like slowly descending a spiral staircase or warmth inching up arms and legs until it blankets the entire body. An alternative method is rapid induction, which is the primary induction used by stage hypnotists. These can be as simple as a handshake and telling the participant to sleep. Rapid inductions rely heavily on the participant’s hypnotizability, which is why many hypnosis shows call up several people but may only hypnotize a few of them. 

Hypnotizability is a bell curve: the hypnotizable, the uninducibles, and the superinducibles. While most people are susceptible to hypnosis, one small portion of the population is nearly impossible to hypnotize, and the other small subset will happily cluck like a chicken onstage. Originally, hypnotizability was believed to be controlled by the brain’s right hemisphere. Instead, newer research shows that it seems to be about brain flexibility, the frontal lobe, and theta waves.

During the initial studies on hypnosis and right brain activity, electroencephalograms (EEGs) showed increased activity throughout the brain among highly hypnotizable people. From this activity emerged a theory: hypnosis selectively activates various cortical and subcortical processes. Subcortical processes generally aggregate information from multiple sources, such as the formation of memories, while cortical processes involve breaking down large amounts of information into pieces. Those who can quickly switch from analytical to holistic thinking are more easily hypnotizable. 

Instead of the right hemisphere, the new study showed that hypnotizable people had increased inhibition of their frontal lobe, the center for voluntary movements and active decision-making. By inhibiting this region, particularly the prefrontal cortex, hypnotists remove the patient from the driver’s seat. Several studies on the default mode network (DMN) build on this idea. The DMN is a group of areas in the brain that activate during non-goal-oriented activity, such as daydreaming, zoning out, and self-reflection. While in a trance, highly hypnotizable people show decreased brain activity in the anterior parts of the DMN. After all, hypnosis is a state of improved focus and concentration where the listener heavily focuses on the hypnotist’s words.

Another significant determinant of hypnotizability is age. Children are practically impossible to hypnotize, likely due to a lack of development in the prefrontal cortex. Hypnotizability peaks in the early 20s, when people are naturally more open to others’ suggestions as they attempt to craft a self-image. It slowly declines until the late 50s, when it sharply decreases. 

Although the mechanisms of hypnosis are not fully understood, continuing study is vital, as hypnosis has many implications in healthcare. Recently, hypnosis has begun to be used in clinical settings to aid those with PTSD, depression, and chronic pain. One trial found that women who have PTSD-induced insomnia were more readily able to fall asleep after receiving sleep-directed hypnosis. Additionally, its most promising usage is as an analgesic. While under hypnosis, certain pain signals will stop firing altogether. Hypnosis could serve as an easier, cheaper painkiller for patients, particularly those with allergies to certain medications. The exploration of the neuroscience behind hypnosis has highlighted the potential benefits of hypnosis in a clinical setting, and there is likely more to be discovered. When compared to the multi-billion-dollar pharmaceutical industry, talk is cheap.

“When compared to the multi-billion-dollar pharmaceutical industry, talk is cheap.”